Molecules and Covalent Bond

1. Covalent bonds are formed when electrons are ……1…… . Covalent compounds have ……2……
electrical conductivity.

Which words correctly complete gaps 1 and 2?

2. The electronic structures of atoms X and Y are shown.

X Y

X and Y form a covalent compound.

What is its formula?

A XY5 B XY3 C XY D X3Y

3. Which diagram does not show the outer shell electrons in the molecule correctly?

A B C D

H H H Cl H C H Cl Cl

1
2

4. Element X has six electrons in its outer shell.

e e key
e = electron
e
e

e e

How could the element react?

A by gaining two electrons to form a positive ion

B by losing six electrons to form a negative ion
C by sharing two electrons with two electrons from another element to form two covalent bonds
D by sharing two electrons with two electrons from another element to form four covalent bonds

5. In which compounds are pairs of electrons shared between atoms?

1 sodium chloride
2 methane
3 lead bromide

A 1 only B 2 only C 1 and 3 D 1, 2 and 3

2
3

6. The diagram shows the electronic structures of atoms P and Q.

e
e e key
e e e e = electron
= nucleus
e e
P e Q e
e e

e e
e

P and Q combine to form a molecule.

What is the formula of this molecule?

A PQ4 B PQ C P2Q D P4Q

7. In the diagrams, circles of different sizes represent atoms of different elements.

Which diagram represents hydrogen chloride gas?

A B C D

8. In the molecules CH4, HCl and H2O, which atoms use all of their outer shell electrons in bonding?

A C and Cl B C and H C Cl and H D H and O

3
4

9. Element X forms an acidic, covalent oxide.

Which row shows how many electrons there could be in the outer shell of an atom of X?

10. Which is a simple covalent molecule?

conducts electricity
volatile
when solid when molten

A   
B   
C   
D   

11. The diagrams show the electron arrangements in the atoms of four elements.

Which element does not form a covalent bond?

A B C
key
e ee ee ee
e electron
ee ee ee ee
e e e nucleus
e e

ee ee ee

4
5

12. Which statement about the bonding in a molecule of water is not correct?

A Both hydrogen and oxygen have a noble gas configuration of electrons.

B Each hydrogen shares its one electron with oxygen.
C Oxygen shares one of its own electrons with each hydrogen.
D Oxygen shares two of its own electrons with each hydrogen.

13. Element X has six electrons in its outer shell.

e e key
e = electron
e
e

e e

How could the element react?

A by gaining two electrons to form a positive ion

B by losing six electrons to form a negative ion
C by sharing two electrons with two electrons from another element to form two covalent bonds
D by sharing two electrons with two electrons from another element to form four covalent bonds

14. Electrons from each element are shared by both of the elements in a compound.

Which compound matches this description?

A lead bromide
B sodium chloride
C water
D zinc oxide

5
6

15. Sodium chloride is an ionic solid.

Which statement is not correct?

A Ions are formed when atoms lose or gain electrons.

B Ions in sodium chloride are strongly held together.
C Ions with the same charge attract each other.
D Sodium chloride solution can conduct electricity.

16. Caesium chloride and rubidium bromide are halide compounds of Group I elements.

Caesium chloride has the formula ……1……, a relative formula mass ……2…… that of rubidium
bromide and bonds that are ……3…… .

Which words correctly complete gaps 1, 2 and 3?

1 2 3

A CaCl different from ionic

B CaCl the same as covalent
C CsCl different from ionic
D CsCl the same as covalent

17. Element X is in Group I of the Periodic Table. X reacts with element Y to form an ionic compound.

Which equation shows the process that takes place when X forms ions?

A X + e – → X+

B X – e – → X–

C X + e – → X–

D X – e – → X+

6
7

18. The electronic structures of atoms X and Y are shown.

X Y

X and Y form a covalent compound.

What is its formula?

A XY5 B XY3 C XY D X3Y

19. In the following diagrams, X and Y are atoms of different elements.

Which diagram correctly shows the arrangement of outer electrons in a molecule of methane?

A B C D

Y Y Y

X Y X Y Y X Y Y X Y

Y Y Y Y

20. In which compounds are pairs of electrons shared between atoms?

1 methane
2 lead bromide
3 sodium chloride

A 1 only B 2 only C 1 and 3 D 1, 2 and 3

7
8

21. Which statement about bonding is not correct?

A Carbon can form four single covalent bonds.

B Chlorine atoms react to gain a noble gas electronic structure.
C Covalent bonding involves losing and gaining electrons.
D Hydrogen molecules have the formula H2.

22. Covalent bonds are formed when electrons are ……1…… .

Most covalent compounds have ……2…… electrical conductivity.

Which words correctly complete gaps 1 and 2?

23. The table shows the electronic structure of four atoms.

Which two atoms combine to form a covalent compound?

A W and X B W and Y C X and Y D X and Z

8
9

24 An atom of element Q contains 19 electrons, 19 protons and 20 neutrons.

What is Q?

A calcium
B potassium
C strontium
D yttrium

25. Which molecule contains only single covalent bonds?

A Cl 2 B CO2 C N2 D O2

26. Ethene is an unsaturated hydrocarbon.

H H

C C

H H

Which description of the bonding in ethene is correct?

A All atoms in the molecule have a share of eight electrons.

B Each carbon atom shares two of its electrons with hydrogen atoms and two of its electrons
with a carbon atom.
C Each carbon atom shares two of its electrons with hydrogen atoms and one of its electrons
with a carbon atom.
D The two carbon atoms share a total of six electrons with other atoms.

9
10

27. Element X forms an acidic, covalent oxide.

Which row shows how many electrons there could be in the outer shell of an atom of X?

28. Which diagram does not show the outer shell electrons in the molecule correctly?

A B C D

H H H Cl H C H Cl Cl

10
11

29 Substances with giant covalent structures can be used as lubricants and as cutting tools for hard
materials.

The diagram shows how the atoms are arranged in two giant covalent substances, X and Y.

X Y

key
strong
covalent
bond
weak
attraction

Which statement is correct?

A Only X is used as a cutting tool and only Y is used as a lubricant.

B Only X is used as a lubricant and only Y is used as a cutting tool.
C X and Y are both used as cutting tools.
D X and Y are both used as lubricants.

30 Which dot-and-cross diagram shows the outer shell electron arrangement in a molecule of
nitrogen?

A B C D

N N N N N N N N

11
12

31 Which dot-and-cross diagram shows the outer shell electron arrangement in a molecule of
carbon dioxide?

A B

O C O O C O

C D

O C O O C O

32 Which dot-and-cross diagram shows the outer shell electron arrangement in a molecule of
carbon dioxide?

A B C D

O C O O C O O C O O C O

33 Which molecule contains exactly two single covalent bonds?

A Cl 2 B CH4 C H2O D HCl

12
13

34 Which electron arrangement for the outer shell electrons in a covalent compound is correct?

A B C D

H Cl H Cl H N H H N H
H H

35 Which statement about a molecule of ammonia, NH3, is correct?

A Each hydrogen atom donates a pair of electrons to a nitrogen atom.

B There are double covalent bonds between the nitrogen atom and the hydrogen atoms.
C There are single covalent bonds between its hydrogen atoms.
D There are three shared pairs of electrons in the molecule.

36 A covalent molecule M contains a total of four shared electrons.

What is M?

A ammonia, NH3
B hydrogen chloride, HCl
C methane, CH4
D water, H2O

13
 14

37 Solid F is an element.
Solid G is a compound.
Neither solid conducts electricity but G conducts electricity when dissolved in water.

These properties suggest that F is ……1…… and that G is ……2…… with ……3…… bonds.

Which words correctly complete gaps 1, 2 and 3?

38 Compound X melts at 801 °C and is a good electrical conductor when dissolved in water.
Compound Y boils at 77 °C, is insoluble in water and is a non-conductor of electricity.

Which type of bonding is present in X and in Y?

14
 15

39 In which row do the properties described match the type of bonding?

electrical conductivity
melting point type of bonding
when liquid

A high does not conduct ionic

B low conducts covalent
C low conducts ionic
D low does not conduct covalent

40 The diagrams, X, Y and Z, show part of a polymer and two giant covalent structures.

X Y Z

Which of X, Y or Z could be used as a cutting tool and which of X, Y or Z could be used to reduce
friction?

15
 16

REVISION WORKSHEET OF BONDING

1 Carbon and silicon are elements in Group IV. Both elements have macromolecular
structures.

(a) Diamond and graphite are two forms of the element carbon.

(i) Explain why diamond is a very hard substance.

....................................................................................................................................

....................................................................................................................................

.............................................................................................................................. [2]

eb
(ii) Give one use of diamond.

nz
.............................................................................................................................. [1]
ha
Ja
za
az
on
M

16
 17

(iii) Explain why graphite is a soft material.

....................................................................................................................................

.............................................................................................................................. [2]

(iv) Give one use of graphite.

............................................................................................................................. [1]

(b) Two of the oxides of these elements are carbon dioxide, CO2, and silicon(IV) oxide,
SiO2.

(i) Draw a diagram showing the arrangement of the valency electrons in one molecule
of the covalent compound carbon dioxide.
Use x to represent an electron from a carbon atom.
Use o to represent an electron from an oxygen atom.

eb
nz
ha
Ja

[3]
za

(ii) A section of the macromolecular structure of silicon(IV) oxide is given below.

az

O
on

Si
M

O O
O

Use this diagram to explain why the formula is SiO2 not SiO4.

....................................................................................................................................

.............................................................................................................................. [2]

(iii) Predict two differences in the physical properties of these two oxides.

....................................................................................................................................

.............................................................................................................................. [2]
17

[Total: 13]
 18

2 The diagrams below show the electron arrangement in two compounds.

+ –
K Cl H O H

(a) In a water molecule, each hydrogen atom is bonded to the oxygen atom by sharing a pair
of electrons.
Why does an oxygen atom share two pairs of electrons rather than just one pair?

...........................................................................................................................................

..................................................................................................................................... [1]

eb
(b) Describe how a potassium atom becomes a potassium ion.

nz
..................................................................................................................................... [1]
ha
(c) Why is there a bond between the ions in potassium chloride?
Ja

...........................................................................................................................................
za

..................................................................................................................................... [1]
az

(d) Solid potassium chloride is a poor conductor of electricity. When dissolved in water it is
a good conductor. Explain.
on

...........................................................................................................................................
M

..................................................................................................................................... [2]

[Total: 5]

18
19

eb
nz
ha
Ja
za

(i) Draw a diagram that shows the formula of this compound, the charges on the ions
az

and the arrangement of the valency electrons around the negative ion.
Use o to represent an electron from an atom of C.
on

Use x to represent an electron from an atom of F.

M

[3]

(ii) Predict two properties of this compound.

[2]

19
[Total: 10]
 20

4 There are three types of giant structure – ionic, metallic and macromolecular.

(a) Sodium nitride is an ionic compound. Draw a diagram that shows the formula of the
compound, the charges on the ions and the arrangement of the valency electrons
around the negative ion.

Use x to represent an electron from a sodium atom.

Use o to represent an electron from a nitrogen atom.

eb
[3]

nz
(b)
b) Describe metallic bonding.
ha
[3]
Ja

(ii) Use the above ideas to explain why

za

metals are good conductors of electricity,

[1]
az

metals are malleable.

on

[2]
M

(c) Silicon(IV) oxide has a macromolecular structure.

(i) Describe the structure of silicon(IV) oxide (a diagram is not acceptable).

[3]

(ii) Diamond has a similar structure and consequently similar properties.

Give two physical properties common to both diamond and silicon(IV) oxide.

[2]
20

[Total: 14]
 21

5 Complete the following table.

electrical electrical
type of
particles present conductivity conductivity of example
structure
of solid liquid

positive and negative

ionic poor
ions

atoms of two different

macro
elements in a giant poor
oor
molecular
covalent structure

eb
nz
metallic and good
ha copper
Ja

[Total: 6]
za
az
on
M

21
 22

6 Magnesium reacts with bromine to form magnesium bromide.

(a) Magnesium bromide is an ionic compound. Draw a diagram that shows the formula of
the compound, the charges on the ions and the arrangement of outer electrons around
the negative ion.
The electron distribution of a bromine atom is 2, 8, 18, 7.

Use x to represent an electron from a magnesium atom.

eb
Use o to represent an electron from a bromine atom. [3]

nz
(b) In the lattice of magnesium bromide, the ratio of magnesium ions to bromide ions is
1:2. ha
(i) Explain the term lattice.
Ja

[2]
za

(ii) Explain why the ratio of ions is 1:2.

az

[1]
on

(iii) The reaction between magnesium and bromine is redox. Complete the sentences.

Magnesium is the agent because it has

M

electrons.

Bromine has been because it has

electrons.
lec

[Total: 10]

22
 23

7 The table shows the melting points, boiling points and electrical properties of the six
substances A to F.

electrical
electrical conductor
conductor of
substance melting point / oC boiling point / oC at room
substance
temperature
dissolved in water

A 961 2193 good does not dissolve

B 113 444 does not conduct does not dissolve

C 0 100 very poor very poor

D 803 1465 does not conduct good

eb
E –5 to -1 102 to 105 good good

nz
F -8 -6 does not conduct does not dissolve
ha
(i) Which three substances are solids at room temperature?
Ja
[1]
za

(ii) Which one is an ionic compound?

[1]
az
on

(iii) Which one is a gas at room temperature?

[1]
M

(iv) Which two substances are liquids at room temperature?

[1]

(v) Which substance is a metal?

[1]

(vi) Which one is an impure substance?

[1]

23
 24

8 (a The structure of a typical ionic compound is a regular arrangement of positive and

negative ions.

– + – +
+ – + –
+ – + –
– + – +
– + – +
+ – + –

(i) What is the name of this regular arrangement of particles?

[1]

eb
(ii) Give two physical properties of ionic compounds.

nz
ha [2]
Ja

(b) Ions are formed by electron loss or gain. The electron distribution of a magnesium
atom is 2 + 8 + 2 and of a nitrogen atom is 2 + 5.
za

(i) Give the formula of the magnesium ion.

az

[1]
on

(ii) Give the formula of the nitride ion.

M

[1]

(iii) What is the formula of the ionic compound, magnesium nitride?

[1]

(iv) In this compound there is an ionic bond. Why are the two ions attracted to each
other?

[1]

24
25

Ions and ionic bonds

1 Which change to an atom occurs when it forms a positive ion?

A It gains electrons.
B It gains protons.
C It loses electrons.
D It loses protons.

2 The electronic configuration of an ion is 2.8.8.

What could this ion be?

S2– Ca2+

A  
B  
C  
D  

3 When sodium chloride is formed from its elements, each chlorine atom ……1…… one ……2…….

Which words correctly complete gaps 1 and 2?

25
 26

4 Which two elements react together to form an ionic compound?

A W and X B X and Y C Y and Z D Z and W

5 The table shows the electronic structures of four atoms.

Which two atoms combine to form an ionic compound?

A W and X B W and Y C X and Y D X and Z

6 The element rubidium, Rb, is immediately below potassium in the Periodic Table.

It reacts with bromine to form the compound rubidium bromide.

Which descriptions of this compound are correct?

26
27

7 The electronic structures of atoms P and Q are shown.

key
P Q = electron

P and Q react to form an ionic compound.

What is the formula of this compound?

A PQ2 B P2Q C P2Q6 D P6Q2

8 The table contains information about four substances.

Which substance is potassium chloride?

9 Rubidium is in Group I of the Periodic Table and bromine is in Group VII.

Rubidium reacts with bromine to form an ionic compound.

Which row shows the electron change taking place for rubidium and the correct formula of the
rubidium ion?

electron change formula of ion formed

A electron gained Rb+

B electron gained Rb–
C electron lost Rb+
D electron lost Rb–
27
 28

10 The electronic structures of atoms P and Q are shown.

P Q

P and Q react to form an ionic compound.

What is the formula of the compound?

A Q7P B QP C QP3 D QP7

11 For which substance is the type of bonding not correct?

type of bonding
substance
ionic
onic cova metallic

A chlorine 
B potassium bromide 
C sodium 
D sodium chloride 

12 Sodium chloride is an ionic solid.

Which statement is not correct?

A Ions are formed when atoms lose or gain electrons.

B Ions in sodium chloride are strongly held together.
C Ions with the same charge attract each other.
D Sodium chloride solution can conduct electricity.

28
 29

13 Caesium chloride and rubidium bromide are halide compounds of Group I elements.

Caesium chloride has the formula ……1……, a relative formula mass ……2…… that of rubidium
bromide and bonds that are ……3…… .

Which words correctly complete gaps 1, 2 and 3?

1 2 3

A CaCl different from ionic

B CaCl the same as covalent
C CsCl different from ionic
D CsCl the same as covalent

14 The electronic structures of two atoms, X and Y, are shown.

X Y

X and Y combine together to form a compound.

What is the type of bonding in the compound and what is the formula of the compound?

15 Element X is in Group I of the Periodic Table. X reacts with element Y to form an ionic compound.

Which equation shows the process that takes place when X forms ions?

A X + e – → X+

B X – e – → X–

C X + e – → X–

D X – e – → X+
29
30

16 Compound X melts at 801 °C and is a good electrical conductor when dissolved in water.

Compound Y boils at 77 °C, is insoluble in water and is a non-conductor of electricity.

Which type of bonding is present in X and in Y?

17 Q+ is an ion of element Q.

What has the highest value in the ion?

A the nucleon number

B the number of electrons
C the number of neutrons
D the proton number

18 Which substance is an ionic compound?

30
31

19 Lithium is in Group I of the Periodic Table. Nitrogen is in Group V of the Periodic Table.

Lithium reacts with nitrogen to form the ionic compound lithium nitride.

What happens to the electrons when lithium atoms and nitrogen atoms form ions?

lithium atoms nitrogen atoms

A each lithium atom loses one each nitrogen atom gains three
electron to form a Li+ ion electrons to form an N3– ion
B each lithium atom loses one each nitrogen atom gains five
electron to form a Li+ ion electrons to form an N5– ion
C each lithium atom gains one each nitrogen atom loses three
electron to form a Li– ion electrons to form an N3+ ion
D each lithium atom gains one each nitrogen atom loses five
electron to form a Li– ion electrons to form an N5+ ion

20 Potassium, K, forms a compound with fluorine, F.

Which statements about this compound are correct?

1 The compound is ionic.

2 The formula of the compound is KF.
3 The compound is soluble in water.

A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

21 Which statement describes positive ions?

A Positive ions have more electrons than neutrons.

B Positive ions have more protons than neutrons.
C Positive ions have more electrons than protons.
D Positive ions have more protons than electrons.

31
 32

22 Which structure represents the sodium chloride lattice?

A B

Na– Cl + Na– Cl + + – + –

Cl + Na– Cl + Na– – + – +

Na– Cl + Na– Cl + + – + –

Cl + Na– Cl + Na– – + – +

C D

– – –
– + – + + + + +
– – –
– – – –
+ – + – + + + +
– – – –
–
–
– + – + + + + +
– – – – –
+ – + – + + + +
– – –
–

23 Magnesium nitride is formed when magnesium burns in air. Magnesium nitride is an ionic
compound.

What is the formula of magnesium nitride?

A MgN2 B Mg2N2 C Mg2N3 D Mg3N2

32
33

24 Which two elements react together to form an ionic compound?

element
element electronic structure

R 2,4
T 2,8
X 2,8,1
Z 2,8,7

A R and T B T and X C X and Z D Z and R

25 Which row describes the type of bonding present in substances 1 and 2?

substance 1 substance 2

A methane has ionic bonding graphite has covalent bonding

B graphite has ionic bonding potassium chloride has covalent bonding
C potassium chloride has ionic bonding methane has covalent bonding
D potassium chloride has ionic bonding graphite has ionic bonding

26 In which row do the properties described match the type of bonding?

electrical conductivity
melting point type of bonding
when liquid

A high does not conduct ionic

B low conducts covalent
C low conducts ionic
D low does not conduct covalent

33
34

27 Four statements about atoms and ions are shown.

1 F– has more electrons than Na+.

2 Mg2+ has the same number of electrons as Na+.
+
3 N has more electrons than Li+.
4 An atom of P has more outer shell electrons than an atom of N.

Which statements are correct?

A 1 and 2 B 1 and 4 C 2 and 3 D 3 and 4

28 Sodium reacts with chlorine to form sodium chloride.

Which statements describe what happens to the sodium atoms in this reaction?

1 Sodium atoms form positive ions.

2 Sodium atoms form negative ions.
3 Sodium atoms gain electrons.
4 Sodium atoms lose electrons.

A 1 and 3 B 1 and 4 C 2 and 3 D 2 and 4

29 The electronic structures of atoms Q and R are shown.

Q R

Q and R form an ionic compound.

What is the formula of the compound?

A QR7 B Q2R4 C QR D Q7R

34
 35

30 Solid F is an element.
Solid G is a compound.
Neither solid conducts electricity but G conducts electricity when dissolved in water.

These properties suggest that F is ……1…… and that G is ……2…… with ……3…… bonds.

Which words correctly complete gaps 1, 2 and 3?

31 The nucleon number and proton number of the lithium atom are shown by the symbol 73 Li.

What is the correct symbol for the lithium ion in lithium chloride?

6 6 7 7
A 2
Li– B 3
Li+ C 3
Li+ D 3
Li–

32 The table shows the structure of different atoms and ions.

particle
articl nucleon number of number of number of
number number protons neutrons electrons

Mg 12 24 12 W 12

Mg2+ X 24 12 12 10

F 9 19 9 Y 9

F– 9 19 9 10 Z

What are the values of W, X, Y and Z?

W X Y Z

A 10 10 9 9
B 10 12 10 9
C 12 10 9 10
D 12 12 10 10
35
36

33 Which element does not form a stable ion with the same electronic structure as argon?

A aluminium
B chlorine
C phosphorus
D potassium

36
37

1 Three ways of making salts are

● titration using a soluble base or carbonate
● neutralisation using an insoluble base or carbonate
● precipitation.
(a) Complete the following table of salt preparations.

method reagent 1 reagent 2 salt

titration ................................... ................................... sodium nitrate

................................... ...................................

B
ZE
neutralisation nitric acid ................................... copper(II) nitrate

AN
...................................

precipitation ................................... ................................... silver(I) chloride

H
JA

................................... ...................................

neutralisation sulfuric acid zinc(II) carbonate ...................................

ZA

...................................
[6]
AZ

(b)
b) Write an ionic equation with state symbols for the preparation of silver(I) chloride.
N

.............................................................................................................................. [2]
O
M

(ii) Complete the following equation.

ZnCO3 + H2SO4 → ............... + ............... + ...............

[2]

[Total: 10]

37
 38

2 Soluble salts can be made by the neutralisation of an acid by a base. Insoluble salts can be
made by precipitation.

(a) The following is a brief description of the preparation of the soluble salt,
nickel(II) chloride-6-water, from the insoluble base nickel(II) carbonate.

Nickel(II) carbonate is added in small amounts to hot dilute hydrochloric acid until it is
in excess. The mixture is filtered. The filtrate is partially evaporated and then allowed to
cool until crystals of nickel(II) chloride-6-water form.

(i) Why is it necessary to use excess carbonate?

....................................................................................................................................

.............................................................................................................................. [1]

B
(ii) Explain why it is necessary to filter.

ZE
.............................................................................................................................. [1]

AN
(iii) Why partially evaporate rather than evaporate to dryness?

....................................................................................................................................
H
JA

.............................................................................................................................. [1]

(iv) What additional steps are needed to obtain dry crystals?

ZA

....................................................................................................................................
AZ

.............................................................................................................................. [2]

(b) Potassium chloride can be made from hydrochloric acid and potassium carbonate.
N
O

(i) Why must a different experimental method be used for this preparation?
M

....................................................................................................................................

.............................................................................................................................. [1]

(ii) Give a description of the different method used for this salt preparation.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

.............................................................................................................................. [4]

38
39

(iii) Two salts of phosphorus acid are its sodium salt, which is soluble in water, and its
calcium salt which is insoluble in water. Suggest a method of preparation for each of
these salts from aqueous phosphorus acid. Specify any other reagent needed and
briefly outline the method.

sodium salt ................................................................................................................

....................................................................................................................................

....................................................................................................................................

.............................................................................................................................. [2]

calcium salt ................................................................................................................

....................................................................................................................................

B
....................................................................................................................................

ZE
.............................................................................................................................. [2]

3- Aluminium sulfate is a soluble salt. AN [Total: 10]

H
Describe how a sample of aluminium sulfate crystals can be prepared from aluminium oxide.
JA

...................................................................................................................................................
ZA

...................................................................................................................................................
...................................................................................................................................................
AZ

...................................................................................................................................................
...................................................................................................................................................
N
O

...................................................................................................................................................
M

...................................................................................................................................................
...................................................................................................................................................
.............................................................................................................................................. [4]

4. Acids are neutralised by alkalis.

(a) Write the ionic equation for the reaction between an acid and an alkali.
...............................................................................................................................................[1]

(b) Sodium sulfate is a soluble salt that can be prepared using a titration method.
(i) Name a sodium compound and the acid that can be used to make sodium sulfate by this
Method.
.............................................................................................................................................[1]

39
40

(ii) Describe how the titration method is used to prepare a colorless solution of
sodium sulfate.
...........................................................................................................................................

...........................................................................................................................................

...........................................................................................................................................

...........................................................................................................................................

...........................................................................................................................................

...........................................................................................................................................

............................................................................................................................................[3]

(iii) Describe how a sample of pure sodium sulfate crystals can be made from aqueous
sodium sulfate.
...........................................................................................................................................

B
...........................................................................................................................................

ZE
...........................................................................................................................................

AN
...........................................................................................................................................

.......................................................................................................................................[2]
H
JA

5- Barium chloride is a soluble salt and barium sulfate is an insoluble salt.

(a) Barium sulfate can be prepared by the reaction between aqueous barium chloride and
ZA

Dilute sulfuric acid.

(i) Describe the preparation of a pure, dry sample of barium sulfate from aqueous
AZ

barium chloride and dilute sulfuric acid.

...........................................................................................................................................
N

...........................................................................................................................................
O

...........................................................................................................................................
M

...........................................................................................................................................

.......................................................................................................................................[3]

(ii) Write the ionic equation, including state symbols, for this reaction.

.......................................................................................................................................[2]

40
41

WORK SHEET 1 /O3

ACIDS AND ALKALIS NAME:
1 Which statements are properties of an acid?
1 reacts with ammonium sulfate to form ammonia
2 turns red litmus blue

1 2

A  
B  
C  
D  
2 Which property is not characteristic of a base?

A It reacts with a carbonate to form carbon dioxide.

B It reacts with an acid to form a salt.
C It reacts with an ammonium salt to form ammonia.
D It turns universal indicator paper blue.

3 A sting from insect X has a pH of 6 and a sting from insect Y has a pH of 8.

The table shows the pH of four substances.

Which substances are used to treat the two stings?

X Y

A hydrochloric acid sodium hydroxide

B sodium hydrogen carbonate vinegar
C sodium hydroxide hydrochloric acid
D vinegar sodium hydrogen carbonate

41
 42

4 Three liquids, P, Q and R, are added to a mixture of hydrochloric acid and Universal Indicator
solution.

The following observations are made.

P the colour of the indicator turns purple.

Q the colour of the indicator does not change.

R there is effervescence and the indicator turns blue.

What are P, Q and R?

5 Which property is not characteristic of a base?

A It reacts with a carbonate to form carbon dioxide.

B It reacts with an acid to form a salt.
C It reacts with an ammonium salt to form ammonia.
D It turns universal indicator paper blue.

42
43

6 The table shows the pH of four aqueous solutions, W, X, Y and Z.

Universal Indicator is added to each solution.

Which row shows the colour of each solution after the indicator is added?

7 Hydrochloric acid is used to clean metals.

The acid reacts with the oxide layer on the surface of the metal, forming a salt and water.

Which word describes the metal oxide?

A alloy
B base
C element
D indicator

43
44

8 Which statement is not correct?

A When a base reacts with an ammonium salt, ammonia is given off.

B When an acid reacts with a base, neutralisation takes place.
C When an acid reacts with a carbonate, carbon dioxide is given off.
D When the acidity of a solution increases, the pH increases.

9 Which reaction is not characteristic of an acid?

A It dissolves magnesium oxide.

B It produces ammonia from ammonium compounds.
C It produces carbon dioxide from a carbonate.
D It produces hydrogen from zinc metal.

10 Which equation for the reaction between sodium carbonate and dilute hydrochloric acid is
correct?

A Na2CO3(s) + HCl (aq) → NaCl (aq) + CO2(g) + H2O(I)

B Na2CO3(s) + HCl (aq) → Na2Cl (aq) + CO2(g) + H2O(I)

C Na2CO3(s) + 2HCl (aq) → NaCl (aq) + CO2(g) + H2O(I)

D Na2CO3(s) + 2HCl (aq) → 2NaCl (aq) + CO2(g) + H2O(I)

44
 45

11 Three chemicals, P, Q and R, were each dissolved in water. The table shows some of the
reactions of these solutions.

reaction when solid sodium reaction when heated with

solution
carbonate is added solid ammonium chloride

P gas evolved no reaction

Q no reaction gas evolved
R no reaction no reaction

The pH of the three solutions was also measured.

What are the correct pH values of these solutions?

P Q R

A 2 7 13
B 2 1 7
C 7 2 13
D 13
3 7 2

12 Which substance is the most acidic?

substance pH

A calcium hydroxide 12
B lemon juice 4
C i
milk 6
D washing up liquid 8

45
 46

13 The graph shows how the pH of soil in a field changes over time.

At which point was the soil neutral?

11 A

pH of 7 B
soil D

5 C

time

14 A colourless solution is tested by the following reactions.

Which reaction is not characteristic of an acid?

A A piece of magnesium ribbon is added. Bubbles are seen and the magnesium disappears.
B A pungent smelling gas is produced when ammonium carbonate is added.
C Copper oxide powder is added and the mixed is warmed. The solution turns blue.
D The solution turns blue litmus red.

15 Which statements about alkalis are correct?

1 When reacted with an acid, the pH of the alkali increases.

2 When tested with litmus, the litmus turns blue.
3 When warmed with an ammonium salt, ammonia gas is given off.

A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

46
47

16 Different plants grow best under different pH conditions.

Which plant grows best in alkaline soil?

grows best in soil at

plant
pH

A ccabbage 6-
B p
potato 4-
C s
strawberry 5-
D wheat
w 6-

17 Which statements about alkalis are correct?

1 When reacted with an acid, the pH of the alkali increases.

2 When tested with litmus, the litmus turns blue.
3 When warmed with an ammonium salt, ammonia gas is given off.

A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

18 Which are properties of an acid?

1 reacts with ammonium sulfate to form ammonia

2 turns red litmus blue

1 2

A  
B  
C  
D  

47
48

19 Carbon dioxide is produced when

X reacts with ethanol.
Y reacts with sodium carbonate.

What are X and Y?

X Y

A H2 HCl
B H2 NaOH
C O2 HCl
D O2 NaOH

20 Ant stings hurt because of the methanoic acid produced by the ant.

Which substance could, most safely, be used to neutralise the acid?

substance pH

A baking soda 8
B car battery acid 1
C lemon juice 3
D oven cleaner 14

48
49

21 The diagram shows an experiment.

blue red
litmus paper litmus paper

aqueous
ammonium chloride
+
aqueous
sodium hydroxide
heat

What happens to the pieces of litmus paper?

blue litmus paper red litmus paper

A changes colour changes colour

B changes colour no colour change
C no colour change changes colour
D no colour change no colour change

49
 50

22 Two indicators, bromophenol blue and Congo red, show the following colours in acidic solutions
and in alkaline solutions.

A few drops of each indicator are added to separate samples of a solution of pH 2.

What are the colours of the indicators in this solution?

23 Which statement about the reaction of acids is correct?

A They react with ammonium salts to form a salt and ammonia only.
B They react with metal carbonates to give a salt and carbon dioxide only.
C They react with metal hydroxides to give a salt and water only.
D They react with metals to give a salt, hydrogen and water only.

24 Which of these pairs of aqueous ions both react with dilute sulfuric acid to give a visible result?

A Ba2+ and Cl

B Ba2+ and CO32

C NH4+ and Cl

D NH4+ and CO32

50
 51

25 Barium hydroxide is an alkali. It reacts with hydrochloric acid.

How does the pH of the hydrochloric acid change as an excess of aqueous barium hydroxide is
added?

A The pH decreases from 14 and becomes constant at 7.

B The pH decreases from 14 to about 1.
C The pH increases from 1 and becomes constant at 7.
D The pH increases from 1 to about 14.

26 The diagram shows two substances, X and Y, being heated together.

damp Universal Indicator

paper

substances X and Y

heat

The Universal Indicator paper turns blue during the experiment.

What are substances X and Y?

A ammonium nitrate and hydrochloric acid

B ammonium nitrate and sodium hydroxide
C sodium carbonate and hydrochloric acid
D sodium carbonate and sodium hydroxide

51
 52

27 A gas is escaping from a pipe in a chemical plant.

A chemist tests this gas and finds that it is alkaline.

What is this gas?

A ammonia
B chlorine
C hydrogen
D sulfur dioxide

28 The graph shows how the pH changes as an acid is added to an alkali.

acid + alkali → salt + water

Which letter represents the area of the graph where both acid and salt are present?

A
14 B
pH

C
7

D
0

29 Dilute hydrochloric acid is added to a solid, S.

A flammable gas, G, is formed. Gas G is less dense than air.

What are S and G?

solid S gas G

A copper
opper hydrogen
B copper carbonate carbon dioxide
C zinc
inc hydrogen
D zinc carbonate carbon dioxide

52
 53

30 An aqueous solution of copper(II) sulfate was made by adding excess copper(II) oxide to dilute
sulfuric acid. The mixture was heated, stirred and then filtered.

dilute copper(II) sulfate

sulfuric acid solution

copper(II) oxide

heat

What was the pH of the acid before adding the copper(II) oxide and of the solution after filtration?

pH of acid before adding pH of solution

copper(II) oxide after filtration

A greater than 7 7
B greater than 7 less than 7
C less than 7 7
D less than 7 greater than 7

31 Which type of reaction always forms a salt and water?

A exothermic
B neutralisation
C oxidation
D polymerisation

53
54

32 An alloy contains copper and zinc.

Some of the zinc has become oxidised to zinc oxide.

What is the result of adding an excess of dilute sulfuric acid to the alloy?

A A blue solution and a white solid remains.

B A colourless solution and a pink / brown solid remains.
C The alloy dissolves completely to give a blue solution.
D The alloy dissolves completely to give a colourless solution.

33 Which is not a typical property of an acid?

A They react with alkalis producing water.

B They react with all metals producing hydrogen.
C They react with carbonates producing carbon dioxide.
D They turn litmus paper red.

34 Which reaction will result in a decrease in pH?

A adding calcium hydroxide to acid soil

B adding citric acid to sodium hydrogen carbonate solution
C adding sodium chloride to silver nitrate solution
D adding sodium hydroxide to hydrochloric acid

54
55

35 The oxide of element X was added to an acid. It reacted to form a salt and water.

oxide of
element X

acid

What is the pH of the acid before the reaction and what type of element is X?

pH type of element X

A greater than 7 metal

B greater than 7 non-metal
C less than 7 metal
D less than 7 non-metal

36 An aqueous solution of the organic compound methylamine has a pH greater than 7.

Which statement about methylamine is correct?

A It neutralises an aqueous solution of sodium hydroxide.

B It reacts with copper(II) carbonate to give carbon dioxide.
C It reacts with hydrochloric acid to form a salt.
D It turns blue litmus red.

55
 56

37 The diagram shows the pH values of four solutions.

Which of these solutions are alkaline?

A P only
B P and Q only
C Q, R and S only
D R and S only

38 The graph shows how the pH of soil in a field changed over time.

At which point was the soil neutral?

11 A

pH of 7 B
soil D

5 C

time

56
57

39 Some reactions of a substance, R, are shown in the diagram.

magnesium
hydrogen

reacts with sodium carbonate

substance R carbon dioxide

copper(II) oxide
copper(II) sulfate

What type of substance is R?

A an acid
B a base
C an element
D a salt

40 Substance K reacts with sodium carbonate to form a gas.

The gas turns limewater cloudy.

What is substance K and which process takes place in the reaction?

K process

A ethanol combustion
B ethanol neutralisation
C hydrochloric acid combustion
D hydrochloric acid neutralisation

57
 58 SALTS PREPARATION WRKSHEET

1 A method used to make copper(II) sulfate crystals is shown.

1 Place dilute sulfuric acid in a beaker.

2 Warm the acid.

3 Add copper(II) oxide until it is in excess.

4 Filter the mixture.
5 Evaporate the filtrate until crystals start to form.
6 Leave the filtrate to cool.

What are the purposes of step 3 and step 4?

step 3 step 4

A to ensure all of the acid has reacted to obtain solid copper(II) sulfate
B to ensure all of the acid has reacted to remove excess copper(II) oxide
C to speed up the reaction to obtain solid copper(II) sulfate
D to speed up the reaction to remove excess copper(II) oxide

2 What is the correct sequence of steps for the preparation of a pure sample of copper(II) sulfate
crystals from copper(II) oxide and sulfuric acid?

A dissolving → crystallisation → evaporation → filtration

B dissolving → evaporation → filtration → crystallisation

C dissolving → filtration → crystallisation → evaporation

D dissolving → filtration → evaporation → crystallisation

3 Salts can be made by adding different substances to dilute hydrochloric acid.

For which substance could any excess not be removed by filtration?

A copper(II) oxide
B magnesium
C sodium hydroxide
D zinc hydroxide

58
 59

4 Four stages in the preparation of a salt from an acid and a solid metal oxide are listed.

1 Add excess solid.

2 Evaporate half the solution and leave to cool.
3 Filter to remove unwanted solid.
4 Heat the acid.

In which order should the stages be carried out?

A 1→3→4→2

B 2→1→3→4

C 4→1→3→2

D 4→2→1→3

5 A salt is produced in each of the following reactions.

P magnesium + dilute hydrochloric acid

Q zinc oxide + dilute sulfuric acid
R sodium hydroxide + dilute hydrochloric acid
S copper carbonate + dilute sulfuric acid

Which statements about the products of the reactions are correct?

1 A flammable gas is produced in reaction P.

2 Water is formed in all reactions.
3 All the salts formed are soluble in water.

A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

6 Zinc sulfate is a soluble salt and can be prepared by reacting excess zinc carbonate with dilute
sulfuric acid.

Which piece of equipment would not be required in the preparation of zinc sulfate crystals?

A beaker
B condenser
C evaporating dish
D filter funnel

59
 60
7 Four steps to prepare a salt from an excess of a solid base and an acid are listed.

1 crystallisation
2 evaporation
3 filtration
4 neutralisation

In which order are the steps carried out?

A 2→
B 3→
C 4→
D 4→

8 Which method is used to make the salt copper sulfate?

A dilute acid + alkali

B dilute acid + carbonate
C dilute acid + metal
D dilute acid + non-metal oxide

9 Which of the following methods are suitable for preparing both zinc sulfate and copper sulfate?

1 Reacting the metal oxide with warm dilute aqueous sulfuric acid.

2 Reacting the metal with dilute aqueous sulfuric acid.

3 Reacting the metal carbonate with dilute aqueous sulfuric acid.

A 1 and 2 only
B 1 and 3 only
C 2 and 3 only
D 1, 2

10 Which two processes are involved in the preparation of magnesium sulfate from dilute sulfuric
acid and an excess of magnesium oxide?

A neutralisation and filtration

B neutralisation and oxidation

C thermal decomposition and filtration
D thermal decomposition and oxidation

60
 61

11 How many different salts could be made from a supply of dilute sulfuric acid, dilute hydrochloric
acid, copper, magnesium oxide and zinc carbonate?

A 3 B 4 C 5 D 6

12 Which salt preparation uses a burette and a pipette?

A calcium nitrate from calcium carbonate and nitric acid

B copper(II) sulfate from copper(II) hydroxide and sulfuric acid

C potassium chloride from potassium hydroxide and hydrochloric acid
D zinc chloride from zinc and hydrochloric acid

13 Which acid reacts with ammonia to produce the salt ammonium sulfate?

A hydrochloric
B nitric
C phosphoric
D sulfuric

14 Copper carbonate reacts with dilute sulfuric acid to make copper sulfate.

CuCO3(s) + H2SO4(aq) → CuSO4(aq) + CO2(g) + H2O(l)

Which row gives the correct order of steps for making copper sulfate crystals?

step 1 step 2 step 3 step 4

A add excess acid to filter evaporate filtrate to leave to cool
the copper carbonate point of crystallisation
B add excess acid to filter evaporate to leave to cool
the copper carbonate dryness
C add excess copper evaporate to point leave to cool filter
carbonate to the acid of crystallisation
D add excess copper filter evaporate filtrate to leave to cool
carbonate to the acid point of crystallisation

15 Which acid reacts with ammonia to produce the salt ammonium sulfate?

A hydrochloric
B nitric
C phosphoric
D sulfuric
61
 62

16 Anhydrous copper(II) sulfate can be made by heating hydrated copper(II) sulfate.

CuSO4.5H2O → CuSO4 + 5H2O

What can be added to anhydrous copper(II) sulfate to turn it into hydrated copper(II) sulfate?

A concentrated sulfuric acid

B sodium hydroxide powder
C sulfur dioxide
D water

17 A compound is a salt if it

A can neutralise an acid.

B contains more than one element.
C dissolves in water.
D is formed when an acid reacts with a base.

18 Salts X and Y are separately dissolved in water.

Samples of the solutions obtained are separately tested with dilute hydrochloric acid and with
aqueous sodium hydroxide.

In two of the tests, a gaseous product is formed. No precipitate is formed in any of the tests.

What are salts X and Y?

X Y

A AgNO3 BaSO4
B BaSO4 Na2CO3
C Na2CO3 NH4Cl
D NH4Cl AgNO3

19 A liquid turns white anhydrous copper sulfate blue and has a boiling point of 103°C.

Which could be the identity of the liquid?

A alcohol
B petrol
C salt solution
D pure water 62
 63

20 A salt is made by adding an excess of an insoluble metal oxide to an acid.

How can the excess metal oxide be removed?

A chromatography
B crystallisation
C distillation
D filtration

21 An excess of copper(II) oxide is added to dilute sulfuric acid to make crystals of hydrated
copper(II) sulfate.

The processes listed may be used to obtain crystals of hydrated copper(II) sulfate.

1 concentrate the resulting solution

2 filter
3 heat the crystals
4 wash the crystals

Which processes are needed and in which order?

A 1, 2
B 1, 2
C 2, 1
D 2, 1

22 Salts can be prepared by reacting a dilute acid

1 with a metal;
2 with a base;
3 with a carbonate.

Which methods could be used to prepare copper(II) chloride?

A 1 and 2 only
B 1 and 3 only
C 2 and 3 only
D 1,
1, 63
 64

1 The energy level diagram for the reaction between sodium hydrogen carbonate and dilute
hydrochloric acid is shown.

sodium chloride + water +

carbon dioxide

energy
sodium hydrogen carbonate +
dilute hydrochloric acid

Which row correctly describes the type of reaction and the energy of the reactants and products?

energy of the reactants

type of reaction
and products

A endothermic the products have more

energy than the reactants

B endothermic the reactants have more

energy than the products

C exothermic the products have more

energy than the reactants

D exothermic the reactants have more

energy than the products

2 The energy level diagram for the reaction between magnesium and hydrochloric acid is shown.

Mg + 2HCl

energy

MgCl 2 + H2

Which statement about the reaction is not correct?

A Energy is given out during the reaction.

B The products are at a lower energy level than the reactants.
C The reaction is endothermic.
D The temperature increases during the reaction.
64
 65

3 The energy level diagram shows the energy of the reactants and products in a chemical reaction.

reactants

energy

products

Which row correctly describes the energy change and the type of reaction shown?

energy change type of reaction

A energy is given out endothermic

to the surroundings
B energy is given out exothermic
to the surroundings
C energy is taken in from endothermic
the surroundings
D energy is taken in from exothermic
the surroundings

4 Which reaction is endothermic?

A acid neutralising alkali causing a temperature increase

B adding magnesium to hydrochloric acid
C calcium carbonate decomposing when heated
D combustion of fossil fuels

65
66

5 Solid hydrated sodium carbonate was added to solid citric acid.

The mixture was stirred and the temperature recorded every 10 seconds.

The results are shown on the graph:

25

20

15
temperature
/ °C
10

0
0 20 40 60 80 100
time / s

Which row describes the reaction?

66
 67

6 Which row correctly describes whether the reaction is exothermic or endothermic?

reaction exothermic endothermic

A calcium carbonate → calcium oxide + carbon dioxide  

B carbon + oxygen → carbon dioxide  
C methane + oxygen → carbon dioxide + water  
D sodium + water → sodium hydroxide + hydrogen  

7 A metal reacts with an aqueous solution.

The graph shows the temperature before, during and after the reaction.

temperature

time

Which row describes the reaction?

67
 68

8 The diagrams show four chemical reactions.

Which reaction is endothermic?

A B

steam flame

water

natural gas
calcium oxide

addition of water to calcium oxide combustion of natural gas

C D

final temperature
initial temperature

alkali

heat acid

thermal decomposition of limestone reaction of acid with alkali

68
 69

9 Limestone can be changed into slaked lime in two chemical reactions.

1 When limestone, CaCO3, is heated it decomposes into lime, CaO.

2 Water is slowly dripped onto the cooled lime. The lime appears to expand and
steam is produced. Slaked lime, Ca(OH)2, is formed.

Which row shows the correct description of each of the chemical reactions?

10 Which statements about exothermic and endothermic reactions are correct?

1 During an exothermic reaction, heat is given out.

2 The temperature of an endothermic reaction goes up because heat is taken in.
3 Burning methane in the air is an exothermic reaction.

A 1, 2 B 1 and 2 only C 1 and 3 only D 2 and 3 only

11 What occurs when a fuel burns?

fuel reacts energy

with oxygen change

A no endothermic
B no exothermic
C yes endothermic
D yes exothermic

69
70

12 Some reactions are endothermic.

How does the temperature and energy change in an endothermic reaction?

temperature change energy change

A decreases energy taken in

B decreases energy given out
C increases energy taken in
D increases energy given out

13 Two chemical processes are described below.

● In the combustion of methane, energy is ......1...... .

● In the electrolysis of molten lead(II) bromide, energy is ......2...... .

Which words correctly complete gaps 1 and 2?

1 2

A given out given out

B given out taken in
C taken in given out
D taken in taken in

14 Solutions of two chemicals are mixed.

A reaction occurs and the temperature change is measured.

Which statement is correct?

A If the reaction is endothermic, the temperature decreases and energy is taken in.
B If the reaction is endothermic, the temperature increases and energy is given out.
C If the reaction is exothermic, the temperature decreases and energy is given out.
D If the reaction is exothermic, the temperature increases and energy is taken in.

70
 71

15 When anhydrous copper(II) sulfate is added to water a solution is formed and heat is given out.

thermometer
anhydrous
copper(II) sulfate

water

Which row correctly shows the temperature change and the type of reaction taking place?

temperature change type of reaction

A decreases endothermic
B decreases exothermic
C increases endothermic
D increases exothermic

16 When ammonium nitrate is added to water the temperature of the water decreases.

The ammonium nitrate can be recovered by evaporating the water added.

Which explains these observations?

A The ammonium nitrate dissolves in the water and the process is endothermic.
B The ammonium nitrate reacts with the water and the process is endothermic.
C The ammonium nitrate dissolves in the water and the process is exothermic.
D The ammonium nitrate reacts with the water and the process is exothermic.

71
 72

17 Some white anhydrous copper(II) sulfate powder is put into a beaker of water and stirred.

What would show that the process was exothermic?

A A blue solution is formed.

B The beaker feels cooler.
C The beaker feels warmer.
D The powder dissolves in the water.

18 The diagrams show the difference in energies of the reactants and products in two types of
reaction.

diagram 1 diagram 2
heat taken in heat given out

products reactants

energy energy
reactants products

Which diagram and which type of energy change apply to a fuel burning in air?

diagram type of energy change

A 1 endothermic
B 1 exothermic
C 2 endothermic
D 2 exothermic

72
73

19 The diagram shows a match.

By striking the match, a chemical reaction takes place.

Which statements about the chemical reaction are correct?

type of reaction reason

A endothermic because energy is used to strike the match

B endothermic because energy is given out as the match burns
C exothermic because energy is used to strike the match
D exothermic because energy is given out as the match burns

20 A diagram for the energy change during an exothermic reaction is shown.

reactants

energy

products

For which reactions would this be an appropriate diagram?

1 CH4 + 2O2 → CO2 + 2H2O

2 2H2 + O2 → 2H2O

3 C + O2 → CO2

A none of them
B 1 and 2 only
C 2 and 3 only
D all of them
73
74

21 The diagram shows the reaction between zinc oxide and dilute hydrochloric acid.

zinc oxide powder

dilute aqueous
hydrochloric acid zinc chloride
20 °C 22 °C
pH 1 pH 7

before after

Which terms describe the reaction?

endothermic neut

A  
B  
C  
D  

22 Acetylene, C2H2, is a hydrocarbon. When acetylene and oxygen react, the hot flame produced
can be used to weld steel.

Which statement is correct?

A Acetylene and oxygen react exothermically.

B Acetylene is saturated.
C Oxygen and steel react endothermically.
D Oxygen is a gaseous fuel.

74
 75

23 Which fuel needs oxygen in order to produce heat energy and which type of reaction produces
the energy?

24 Some reactions are listed.

methane + oxygen → carbon dioxide + water

sodium + water → sodium hydroxide + hydrogen

magnesium + hydrochloric acid → magnesium chloride + hydrogen

Which word correctly describes all of these reactions?

A combustion
B endothermic
C exothermic
D neutralisation

25 Which is an endothermic process?

A burning hydrogen
B distilling petroleum
C reacting potassium with water
D using petrol in a motor car engine

75
 76

26 The diagrams show some pieces of laboratory equipment.

1 2 3
balance stop-clock thermometer

60
45 15
30

Which equipment is needed to find out whether dissolving salt in water is an endothermic
process?

A 1 only B 1 and 3 C 2 and 3 D 3 only

27 Clouds are formed when water vapour evaporates from the sea.

clouds

water vapour

sea

What is the energy change and what name is given to the type of change when water
evaporates?

energy change type of change

A energy given out endothermic

B energy given out exothermic
C energy taken in endothermic
D energy taken in exothermic

76
77

28 Which process is not exothermic?

A burning a fossil fuel

B obtaining lime from limestone
C radioactive decay of 235U
D reacting hydrogen with oxygen

29 When an acid is added to an alkali the temperature rises.

Which words describe this reaction?

A decomposition and endothermic

B decomposition and exothermic
C neutralisation and endothermic
D neutralisation and exothermic

30 Which diagram shows a process in which an endothermic change is taking place?

A B C D

ice sodium
rocket
candle

water

water

77