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GEMS AKADEMIA GLOBAL SCHOOL

Work sheet _ 2024-25

Subject: CHEMISTRY Grade: 10 CAIE

SECTION-A

3 The chromatogram obtained using four substances, J, K, L and M, is shown. Which statement about
M is correct?
A. It is a mixture of J and K only.
B. It is a pure substance.
C. It is a mixture of J, K and L.
D. It is a mixture of J, K and an unknown
substance.
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4 Which statements about isotopes of the same element are correct?

1-They are atoms which have the same chemical properties because they have the same number of
electrons in their outer shell.
2-They are atoms which have the same number of electrons and neutrons but different numbers of
protons.
3-They are atoms which have the same number of electrons and protons but different numbers of
neutrons.
A. 1 and 2
B 1and 3
C 2 only
D 3 only
5 Which molecule contains only three shared pairs of electrons?
A. CH3OH B. Cl2 C. H2O D. N2
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15 Which element forms an oxide that reacts with an aqueous solution of a base?
A. argon
B. sulfur
C. magnesium
D. copper
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SECTION B
1 Table 1.1 gives the electronic configurations of some atoms and ions, A to G.
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Answer the following questions about A to G.

Each letter may be used once, more than once or not at all.
State which of the atoms or ions, A to G, could be:
(a) a noble gas atom
(b) an atom of an element in Group VI
(c) an atom with an atomic numtH of 14
(d) atoms from the same group
(e) a halogen atom
(f) an atom of an element which is a conductor of electricity
(g) a stable ion of a Group V element
(h) an atom that forms an ion with a 2— charge-
2 Sodium is a reactive metal.
(a) Suggest why sodium is stored under oil.
(b) Sodium burns in air to form sodium oxide, N2O.
(i) State the term given to a reaction in which a substance burns.
(ii) State the colour of the flame seen when sadium bums.
(iii) Write a chemical equation for the reaction which takes place when sodium bums in air to
form sodium oxide.
(iv) Complete the dot-and-cross diagram to show the electron arrangement and charges of
the ions in sodium oxide.
(c) Sodium reacts vigorously with water to form aqueous sodium hydroxide, NaOH, which is a
strong base.
(i)Explain in terms of proton transfer what is meant by a base.
(ii) State a pH number that indicates the presence of a strong alkali.
(iii) State the colour of methyl orange in aqueous sodium hydroxide.
(iv) The equation for the reaction is shown.

Calculate the concentration of NaOH(aq) formed, in g/dm3, when 0.345g of sodium is

added to 50.0 cm3 of distilled water. Assume there is no change in volume.
IJse the following steps.
 Calculate the number of moles of Na added.
 Determine the number of moles of NaOH formed.
 Calculate the concentration of NaOH in mol/dm3
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 Explain why lead(ll) chloride needs to be molten before it will conduct electricity
 Write the ionic half equation for the reaction occurring at the anode.
 State the test for chlorine gas.
 Describe what is observed at the cathode.
4 (a) Thymolphthalein is an indicator. State the colour of thymolphthalein in:
i. NaOH(aq)
ii. CH3COOH(aq).
(b) (i)use the information in Table to identify the substance with the highest concentration of H+(aq)
ions. Explain your answer.
(ii) Name an indicator which can be used to identify the substance with the highest
concentration of H+(aq) ions.
(e) Complete the equation to show the dissociation of ethanoic acid, CH3COOH, in aqueous
solution.
(f) Write the ionic equation which represents a neutralisation reaction between any acid and any
alkali.
5 Chemical reactions can involve transfer of thermal energy.
(a) State the term used for the transfer of thermal energy during a reaction.
(b) Tetrachloromethane gas, CC14(g), reacts with steam as shown.

(i) State what happens, if anything, to the rate of the forward reaction if the concentration of
CCl4 is increased. Explain your answer in terms of collision theory.
(ii) State what happens to the position of equilibrium, if anything, when the pressure is
increased. Explain your answer.
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Calculate the energy needed to break the bonds in the reactants.

Calculate the energy released when the bonds in carbon dioxide form.
Calculate the H—CI bond energy.
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8 Compound X is a colourless liquid at room temperature.

(a) A sample of pure X was slowly heated from —5.0 °C, which is below its melting point, to 90 °c,
which is above its boiling point. Its temperature is measured every minute and the results are
represented on the graph.

(b)What is the significance of temperature t °C?

(c)What is the physical state of compound X in the region EF?
(d)What would be the difference in the region BC if an impure sample of X had been used?

9 Explain the following in terms of the kinetic particle theory

A liquid has a fixed volume but takes up the shape of the container. A gas takes up the shape
of the container but it does not have a fixed volume.
10 The table below gives information about particles.
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(a) Complete the table. The first line has been done for you.

(b)

11 Complete the following table which gives the number of protons, electrons and neutrons in each
of the five particles.

12 (a) Fluorine reacts with sulfur to form a compound which has 25.2% sulfur by mass and a relative
molecular mass of 254. Determine the molecular formula of this compound.
(b) Nitrogen trichloride, NCl3, is a covalent compound. Complete the dot-and-cross diagram to show
the electron arrangement in a molecule of NCl3.
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(d) Lithium chloride, LiCl, is an ionic compound. Complete the dot-and-cross diagram to show the
electron arrangement and charges of the ions in lithium chloride.
(e) Explain, in terms of attractive forces between particles, why LiCl is a solid at room temperature.
But NCl3 is a liquid with a relatively low boiling point.
13 (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?
(b) Describe how a potassium atom becomes a potassium ion.
(c) Why is there a bond between the ions in potassium chloride?
(d) Solid potassium chloride is a poor conductor of electricity. When dissolved in water it is
a good conductor. Explain.
14 During electrolysis, ions move in the electrolyte and electrons move in the external circuit.
Reactions occur at the electrodes.
(a) The diagram shows the electrolysis of molten lithium iodide.

(i) Draw an arrow on the diagram to show the direction of the electron flow in the external circuit.
(ii) Electrons are supplied to the external circuit. How and where is this done?
(iii) Explain why solid lithium iodide does not conduct electricity but when molten it is a
good conductor.
(b) The results of experiments on electrolysis are shown in the following table. Complete the
table. The first line has been done as an example.

14 Cobalt is an element in Period 4 of the Periodic Table.

(a) Use your copy of the Periodic Table to help you complete the table below.
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(b) 60Co is a cobalt isotope.

(i) Explain the term isotope.
(ii) Explain why two isotopes of the same element have identical chemical properties.
15 The following table gives information about six substances.

 Which substance could have a macromolecular structure, similar to that of silicon(IV) oxide?
 Which substances are solids at room temperature?
 Which substance could be a metal?
 Which substance could be aqueous sodium chloride?
 Which substance is an ionic compound?
 Which substances are liquids at room temperature?
16 Ethanoic acid is a colourless liquid at room temperature. It has the typical acid properties
and forms compounds called ethanoates.
(a) A pure sample of ethanoic acid is slowly heated from O°C to 150°C and its temperature
is measured every minute. The results are represented on the graph below.

Name the change that occurs in the region D to E.

What would be the difference in the region B to C if an impure sample had been used?
Sketch on the graph how the line would continue if the acid was heated to a higher temperature.
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(i) Which one, magnesium or ethanoic acid, is in excess? You must show your
reasoning.
(ii) How many moles of hydrogen were formed?
(iii) Calculate the volume of hydrogen formed, measured at r.t.p.
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(i) Calculate the number of moles of NaOH in 25.0 cm3 of 0.4mol/dm3 solution.
(ii) Use your answer to (i) and the mole ratio in the equation to find out the number of
moles of H2C204 in 20 cm3 of solution.
(iii) Calculate the concentration, mol/dm3, of the aqueous oxalic acid.
19 This question is about chemical reactions and electricity.
(a) The diagram shows the apparatus used in the production of electrical energy in a simple cell.

The zinc electrode dissolves in the electrolyte forming Zn2+(aq) ions.

(i) Draw an arrow on the diagram to show the direction of electron flow.
(ii) Write the ionic half-equation for the reaction that occurs when the zinc electrode dissolves.

(b) The reading on the voltmeter can be increased if either zinc or iron is replaced by another
metal.
(i)Name a metal that can replace zinc and increase the reading on the voltmeter.
(ii) Name a metal that can replace iron and increase the reading on the voltmeter.

(c) Fuel cells are used to generate electricity.

(i) Name the reactants in a fuel cell.
(ii) Name the waste product of a fuel cell.

(d) Electricity can be used to break down aqueous or molten ionic compounds.
(i) Name the process which uses electricity to breakdown aqueous or molten ionic compounds.
(ii) Explain why the ionic compound needs to be aqueous or molten.

(e) Brine is concentrated aqueous sodium chloride.

(i) Name three substances which are manufactured by passing electricity through brine.
(ii) Name a different substance formed when molten sodium chloride is used instead of
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concentrated aqueous sodium chloride.

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(a) Alumina is obtained from the main ore of aluminium. Name this ore.
(i) Explain why it is necessary to use a mixture, alumina and cryolite, rather than just alumina.
(ii) Copper can be extracted by the electrolysis of an aqueous solution.
Suggest why the electrolysis of an aqueous solution cannot be used to extract
aluminium.
(b) The ions which are involved in the electrolysis are Al3+ and O2-. The products of this
electrolysis are given on the diagram. Explain how they are formed. Use equations where
appropriate.
(c) The uses of a metal are determined by its properties.
(i) Foods which are acidic can be supplied in aluminium containers.
21 The electrolysis of concentrated aqueous sodium chloride, between inert electrodes, is used
to make four important chemicals.
hydrogen
chlorine
sodium hydroxide
sodium chlorate(l)
(a) The ions present in the electrolyte are Na+, H+, Cl- and OH-
(i) Hydrogen ions are discharged at the negative electrode (cathode). Write an equation for this
reaction.

(iii) When a dilute solution of sodium chloride is used, chlorine is not formed at the
positive electrode (anode), a different gas is produced. Name this gas.
(iv) State an example of an inert electrode.

22 The results of experiments on electrolysis using inert electrodes are given in the table.
Complete the table; the first line has been completed as an example.
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23 Calcium reacts with nitrogen to form the ionic compound calcium nitride, Ca3N2
(a) Draw a diagram, based on the correct formula, which shows the charges on the ions and the
arrangement of the electrons around the negative ion.
Use o to represent an electron from a calcium atom.
Use x to represent an electron from a nitrogen atom.
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(a) Explain in terms of its structure why graphite is soft and is a good conductor of electricity.
(b) State two uses of graphite which depend on the above properties.
(c) Silicon(IV) oxide also has a macromolecular structure.
(i) Describe the macromolecular structure of silicon(IV) oxide.
(ii) Predict two physical properties which diamond and silicon(IV) oxide have in common.
25 Calcium hydroxide, is slightly soluble in water.
(a) Calcium hydroxide can be made by the reaction of calcium with water-
i. Write the chemical equation for this reaction.
ii. Name another substance that reacts with water to form calcium hydroxide.
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(b) When calcium hydroxide dissolves in water, it dissociates into ions and forms a weakly alkaline
solution-
i. Suggest the pH of aqueous calcium hydroxide.
ii. Give the formula of the ion responsible for making the solution alkaline.

(c) Limewater is a saturated solution of hydroxide,

i. Name the gas limewater is used to test for.
ii. Suggest what is meant by the term saturated
iii. Describe how you would make a sample of limewater starting with solid calcium hydroxide.
iv. Describe how you would test for the presence of calcium ions in a sample of limewater.
Test observations
26 Nitrogen can form ionic compounds with reactive metals and covalent compounds with non-metals.
(a) Nitrogen reacts with lithium to form the ionic compound lithium nitride, Li 3N.
(i) Write the equation for the reaction between lithium and nitrogen.
(ii) Lithium nitride is an ionic compound. Draw a diagram which shows its formula, the charges
on the ions and the arrangement of the valency electrons around the negative ion.
Use x for an electron from a lithium atom.
Use o for an electron from a nitrogen atom.
(b) Nitrogen fluoride is a covalent compound.
(i) Draw a diagram showing the arrangement of the valency electrons in one molecule of the
covalent compound nitrogen trifluoride, NF3.
Use x for an electron from a nitrogen atom.
Use o for an electron from a fluorine atom.
27 In the Periodic Table, the elements are arranged in columns called Groups and in rows called
Periods.
(a) Complete the table for some of the elements in Period 3.

(ii)What is the relationship between the group number and the number of valency electrons?
(iii)Explain the relationship between the number of valency electrons and the valency
 for the elements Na to Al
 for the elements P to Cl.

(b) Across a period, the elements change from metallic to non-metallic.

(i) Describe how the type of oxide changes across this period.
28 Over 200 million tonnes of sulfuric acid are manufactured every year.
(a) State the name of the process used to manufacture sulfuric acid.
(b) Part of the manufacture of sulfuric acid involves converting sulfur dioxide to sulfur trioxide.
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(i) Describe two methods by which sulfur dioxide is obtained.

The conversion of sulfur dioxide to sulfur trioxide is a reversible reaction which can reach
equilibrium.
(ii)Complete Table to show the effect, if any, when the following changes are applied to
the conversion of sulfur dioxide to sulfur trioxide.

The forward reaction is exothermic

Only use the words increases, decreases or no change.

(iii) Explain in terms of collision theory why reducing the temperature decreases the rate of the
forward reaction.
(iv) Sulfuric acid contains SO42- ions.
The oxidation number of O atoms in SO42- ions is —2.
Determine the oxidaüon nurntM of S atoms in SO42- ions. Show your working.
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(b) Suggest two reasons why a temperature lower than 7000C is not used.
(c) Suggest one advantage of using a pressure greater than one atmosphere.
(d) Suggest one disadvantage of using a pressure greater than one atmosphere.
(e) Hydrogen can also be manufactured by electrolysis. The electrolyte is concentrated aqueous
sodium chloride. The electrodes are inert.
The products of electrolysis are hydrogen, chlorine and sodium hydroxide.
 Define the term electrolysis
 Name a substance that can be used as the inert electrodes.
 Write an ionic half-equation for the reaction in which hydrogen is produced.