2.2.2 Bonding and Structure PhysicsAndMathsTutor.
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Bonding and Structure
1. Phosgene, COCl2, exists as simple molecules.
The displayed formula of a phosgene molecule is shown below.
i. Draw a ‘dot-and-cross’ diagram of a phosgene molecule.
Show outer electrons only.
[1]
ii. Name the shape of a phosgene molecule and explain why it has this shape.
Name of shape
Explanation
[3]
2(a). Sodium sulfide, Na2S, is an ionic compound of sodium, Na, and sulfur, S.
Draw a ‘dot-and-cross’ diagram to show the bonding in sodium sulfide.
Show outer electrons only.
[2]
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(b). The table below compares the properties of sodium sulfide, sodium and sulfur.
Complete the table.
Sodium sulfide Sodium Sulfur
Melting point / °C 1180 98 113
Type of structure
(giant or simple)
solid
Electrical
conductivity liquid
(good or poor)
[3]
3. Solid barium chloride has a high melting point. Barium chloride dissolves in water to form a
solution that can be used to test for sulfate ions.
i. Draw a ‘dot-and-cross’ diagram to show the bonding in solid barium chloride.
Show outer electrons only.
[2]
ii. A solution of barium chloride can be made in the laboratory using dilute hydrochloric
acid.
Suggest a compound that can be reacted with hydrochloric acid to make barium
chloride.
[1]
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4. Bromine is a reactive element. It combines with other non-metals to form covalent compounds.
Phosphorus tribromide, PBr3, and iodine monobromide, IBr, are examples of covalent
compounds used in organic synthesis.
PBr3 can be prepared by heating bromine with phosphorus, P4.
i. Write an equation for this reaction.
[1]
ii. How many molecules are present in 1.3535 g of PBr3?
number of molecules = ..........................................[3]
iii. The ‘dot-and-cross’ diagram of a molecule of PBr3 is given below.
Name the shape of this molecule and explain why the molecule has this shape.
name:
explanation:
[3]
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5. The hydroxyl group, –OH, is responsible for many properties of alcohols.
Methanol, CH3OH, is soluble in water because it has polar bonds.
Pauling electronegativity values for carbon, oxygen and hydrogen are shown below.
Element Electronegativity
Carbon 2.5
Oxygen 3.5
Hydrogen 2.1
Use a labelled diagram to explain why methanol is soluble in water.
• Use displayed formulae showing one molecule of methanol and one molecule of water.
Add partial charges δ+ and δ – to show the two most polar bonds in a methanol molecule and
•
the polar bonds in a water molecule.
• Show all lone pairs.
• Label the most important intermolecular bond between the molecules.
[2]
6. The displayed formula for propanoic acid is shown below.
i. State the shape and bond angle around a carbon atom in the alkyl group of propanoic
acid. Explain the shape.
Shape
Bond angle
Explanation
[2]
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ii. Suggest a value for the C–O–H bond angle in propanoic acid.
[1]
7. Barium combines with oxygen, chlorine and nitrogen to form ionic compounds.
Barium oxide, BaO, has a giant ionic lattice structure.
i. State what is meant by the term ionic bond.
[1]
ii. Draw a ‘dot-and-cross’ diagram to show the bonding in barium oxide.
Show outer electrons only.
iii. Calculate the number of barium ions in 1.50 g of barium oxide.
Give your answer in standard form and to three significant figures.
number of barium ions = .......................................................
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8(a). At room temperature and pressure, the first four members of the alkanes are all gases but the
first four alcohols are all liquids.
Explain this difference in terms of intermolecular forces.
[2]
(b). The boiling points of 2-methylpropan-1-ol and butan-1-ol are shown below.
Boiling point /
Alcohol
°C
2-methylpropan-1-ol 108
butan-1-ol 117
Explain why the boiling points are different.
[2]
9. Nickel(II) nitrate, Ni(NO3)2, can be prepared by reacting nickel(II) oxide with dilute nitric acid.
i. Write the equation for this reaction.
[1]
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ii. Ni(NO3)2 contains the NO3− ion. The nitrogen atom bonds to the oxygen atoms with a
single covalent bond, a double covalent bond and a dative covalent bond, as shown
below.
Draw the ‘dot‐and‐cross‘ diagramfor the NO3− ion, showing outer shell electrons only.
Use a different symbol for the extra electron.
[2]
10. Compounds of calcium have many uses.
i. Identify a compound of calcium that could be used to convert a soil pH from 5.8 to 7.5.
[1]
ii. Calcium phosphide, Ca3P2, is an ionic compound used in rat poison.
Calcium phosphide can be prepared by reacting calcium metal with phosphorus, P4.
Write the equation for the reaction of calcium with phosphorus to form calcium
phosphide.
[1]
iii. Draw a ‘dot-and-cross’ diagram to show the bonding in calcium phosphide, Ca3P2.
Show outer electrons only.
[2]
11. i. Fluorine is the most electronegative element.
Indicate any dipoles on the molecule of F2O below using partial charges.
[1]
ii. Suggest the shape of the F2O molecule and the F−O−F bond angle.
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Shape ...............................................................
Bond angle ...........................................................
[1]
iii. What is the oxidation number of oxygen in F2O?
Include the sign in your answer.
[1]
12. This question is about halogens.
Solid chlorine and solid bromine have a similar structure.
Name this structure.
[1]
13. Draw a ‘dot-and-cross’ diagram to show the bonding in a nitrogen molecule.
Show outer electrons only.
[1]
14 This question is about the properties and reactions of butan-2-ol.
.
Some properties of butan-2-ol are listed in the table.
Melting point −115 °C
Boiling point 99.5 °C
The shape around the oxygen atom in butan-2-ol is non-linear.
Predict the C−O−H bond angle and explain this shape.
2.2.2 Bonding and Structure PhysicsAndMathsTutor.com
bond angle ...........................................................
explanation
................................................................................................................................
..................
[4]
15. The graph shows the melting points of the elements in Period 3 of the periodic table.
Phosphorus and chlorine have simple molecular structures.
More information about phosphorus and chlorine is given in the table below.
Element Molecular formula
phosphorus P4
chlorine Cι2
Explain the differences in the melting points of phosphorus and chlorine.
2.2.2 Bonding and Structure PhysicsAndMathsTutor.com
[3]
16. The table shows the boiling points of ammonia, fluorine and bromine.
Boiling point / °C
ammonia, NH3 – 33
fluorine, F2 – 188
bromine, Br2 59
Explain the different boiling points of NH3, F2 and Br2.
Include the names of any relevant forces and particles.
In your answer you should use appropriate technical terms, spelled correctly.
[5]
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17. Chlorine gas reacts with methane. One of the products is dichloromethane, CH2Cl2.
i. Chlorine is more electronegative than carbon and hydrogen, which have approximately
equal electronegativity values.
Explain what is meant by the term electronegativity.
[2]
ii. Draw a 3-D diagram of a molecule of CH2Cl2.
Use partial charges to indicate polar bonds.
[2]
iii. Explain why a CH2Cl2 molecule is polar.
[1]
18(a). Solid aluminium fluoride has a giant ionic lattice structure.
i. Describe what is meant by the term ionic lattice, in terms of the type and arrangement of
particles present.
[2]
2.2.2 Bonding and Structure PhysicsAndMathsTutor.com
ii. Draw a ‘dot-and-cross’ diagram for aluminium fluoride.
Show outer electrons only.
[2]
(b). Solid boron tribromide has a simple molecular lattice structure. The atoms are held together by
covalent bonds.
i. What is meant by the term covalent bond?
[1]
ii. Draw a ‘dot-and-cross’ diagram to show the bonding in a boron tribromide molecule.
Show outer electrons only.
[1]
19 A chemist carries out reactions of barium and barium nitride, Ba3N2.
.
Reaction 1 Barium is reacted with water.
Reaction 2 Barium nitride is reacted with water, forming an alkaline solution and an alkaline gas.
Reaction 3 Barium is reacted with an excess of oxygen at 500°C, forming barium peroxide, BaO2.
i. Write equations for Reaction 1 and Reaction 2.
Ignore state symbols.
Reaction 1:
.....................................................................................................................
.......................
Reaction 2:
2.2.2 Bonding and Structure PhysicsAndMathsTutor.com
.....................................................................................................................
.......................
[3]
ii. Predict the structure and bonding of Ba3N2.
[1]
iii. BaO2 formed in Reaction 3 contains barium and peroxide ions.
The peroxide ion has the structure [O−O]2−.
Suggest a ‘dot-and-cross’ diagram for BaO2.
Show outer shell electrons only.
[1]
20(a). Oxides can have different types of bonding.
H2O has hydrogen bonding.
i. Complete the diagram below to show hydrogen bonding between the H2O molecule
shown and one other H2O molecule.
Include relevant dipoles and lone pairs.
Label the hydrogen bond.
[2]
ii. State and explain two anomalous properties of ice caused by hydrogen bonding.
1
2.2.2 Bonding and Structure PhysicsAndMathsTutor.com
[4]
(b). Draw a ‘dot-and-cross’ diagram to show the bonding in CO2.
Show outer electrons only.
[1]
21 Antimony chloride, SbCl3, exists as simple covalent molecules.
.
A ‘dot-and-cross’ diagram of SbCl3 is shown below.
i. Predict the shape of a molecule of SbCl3.
Explain your answer.
name of shape:
.....................................................................................................................
..................
explanation:
.....................................................................................................................
.....................
[3]
2.2.2 Bonding and Structure PhysicsAndMathsTutor.com
ii. SbCl3 molecules are polar.
Explain why.
[2]
22(a). The graph below shows the variation in boiling points of the Group 16 hydrides.
i. The variation in boiling point can be explained by intermolecular bonding.
Explain why H2S has a lower boiling point than H2O and H2Se.
[4]
2.2.2 Bonding and Structure PhysicsAndMathsTutor.com
ii. Polonium, Po, is at the bottom of Group 16. Its hydride has the formula H2Po.
Estimate from the graph the boiling point of H2Po.
The relative molecular mass of H2Po is 211.
[1]
(b). The compounds SO2 and MgO both contain oxygen.
The table below shows the melting point of both compounds:
Compound Melting point / K
SO2 200
MgO 3125
Predict the type of structure and bonding of SO2 and MgO and explain the difference in their
melting points.
[4]
23. Carbon monoxide contains a triple bond, and includes a dative covalent bond.
Construct a ‘dot-and-cross’ diagram to show the outer electron pairs in a molecule of carbon
monoxide.
[2]
END OF QUESTION PAPER
