CIE AS Chemistry

Topic Questions

ASChemistryCIETopic Questions1. Physical Chemistry1.4 States of Matter

Syllabus Edition

First teaching 2020

Last exams 2024

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1.4 States of Matter

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1a4 marks

This question is about gases.

i)
Describe the arrangement and movement of particles in a gas.

[3]

ii)
Explain why gases exert a pressure.

[1]

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1b1 mark
As the volume of a gas is changed, the pressure of the gas changes. A graph of the volume of gas against 1 over pressure at constant temperature is shown in Fig. 1.1.

1-4-1b-e-temp-vs-1pressure

Fig. 1.1

What relationship does the graph in Fig. 1.1 show between the volume of gas and pressure at constant temperature?

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1c2 marks

Changing the temperature of a gas, at a constant volume, will affect the volume of the gas.
 
Draw the relationship between the temperature and the volume of the gas on Fig 1.2.

 

1-4-1d-e-temp-vs-pressure-a

Fig. 1.2

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2a2 marks

Two assumptions made about ideal gas behaviour are that ideal gases have zero particle volume and no intermolecular forces of attraction

Explain why helium comes very close to ideal gas behaviour.

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2b6 marks

The ideal gas equation is pV = nRT where R is the molar gas constant with a value of 8.31 J K–1 mol–1.

Explain as fully as you can the meaning of the following terms, and give the units for each to correspond with the value of R.

p ..............................................................................................
  ..............................................................................................
V ..............................................................................................
  ..............................................................................................
T ..............................................................................................
  ..............................................................................................

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2c
Sme Calculator3 marks

Calculate the volume, in dm3, of one mole of helium gas at 10 °C and 92.0 kPa.
Give your answer to 3 significant figures.
Show your working.



volume of one mole of helium gas = ............................................... dm3

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3a2 marks
Sodium ions and chloride ions form a giant ionic lattice in solid form. Sodium ions are smaller than chloride ions.

Complete the diagram to show the location of the ions in the lattice of solid sodium chloride.

 

2-4_q2c-ocr-a-as--a-level-easy-sq

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3b2 marks

Explain the strength of the ionic bond in sodium chloride.

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3c3 marks

Magnesium fluoride is another compound that forms a giant ionic lattice in solid form.

Predict the electrical conductivity of magnesium fluoride in each of the following states:

 
State Electrical conductivity (Y / N)
Solid  
Liquid  
Aqueous  

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3d2 marks

Explain why it is easier to use aqueous MgF2 than molten MgF2 in a laboratory setting.

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4a5 marks

This question is about crystalline solids.

Iodine and diamond are crystalline solids at room temperature.


Explain why diamond has a much higher melting temperature than iodine.

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4b2 marks

Graphite is also a crystalline solid at room temperature.

Unlike diamond, graphite conducts electricity.

Describe the key feature of the bonding of the carbon atoms in graphite that results in it being an electrical conductor.

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4c4 marks

State the type of structure that is likely to be present in the following:

i)
Crystalline solid that conducts electricity, is malleable and has a melting point of 900 °C.

[1]

ii)
Crystalline solid that does not conduct electricity and has a melting point of 92 °C.

[1]

iii)
Crystalline solid that does not conduct electricity and has a melting point of more than 3100 °C.

[1]

iv)
Crystalline solid that does not conduct electricity and has a melting point of 790 °C. When molten it becomes a conductor.

[1]

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5a4 marks

Carbon and silicon are both in Group 14.

Diamond and graphite are two forms of the element carbon.

Explain why diamond is a hard substance but graphite is soft.

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5b2 marks

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

Predict two differences in the physical properties of these two oxides.

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5c2 marks

Silicon(IV) oxide is not soluble in water but magnesium oxide is soluble in water.

Explain why magnesium oxide is soluble in water.

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1a
Sme Calculator1 mark

Phosphine, PH3, is a gas formed by heating phosphorous acid, H3PO3, in the absence of air.

4H3PO3 (s) → PH3 (g) + 3H3PO4 (s)

 

State the shape and bond angle in PH3 (g).

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1b
Sme Calculator3 marks

3.45 × 10−2 mol of H3PO3 is completely decomposed at 100 kPa pressure and 210 °C.

 

Calculate the volume occupied, in cm3, by the phosphine gas produced.

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1c
Sme Calculator3 marks

1.85 g of white phosphorus was reacted with 75.00 cm3 of 1.25 mol dm-3 sodium hydroxide solution to make phosphine.

P4 (s) + 3OH− (aq) + 3H2O (l) → PH3 (g) + 3H2PO2− (aq)

Deduce which chemical is the limiting reagent.  

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1d
Sme Calculator1 mark

Use the information in part (c) to calculate the volume, in cm3, of phosphine that was produced at room temperature and pressure.  Give your answer to three significant figures.

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2a
Sme Calculator2 marks

Oxygen exists as a diatomic gas, O2 (g). A sample of O2 (g) was made during a chemical reaction. When measured at 303 kPa and 28 °C the sample occupied a volume of 95.0 cm3.

Calculate the mass of oxygen formed.

 

For this calculation, assume that oxygen behaves as an ideal gas under these conditions.

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2b
Sme Calculator2 marks

Calculate the number of electrons involved in the bonding of this sample of oxygen. You may find it helpful to use your answer to (a).

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2c2 marks

O2 (g) does not behave as an ideal gas under these conditions. 

 

Explain why O2 (g) behaves even less ideally at:

  • very high pressures
  • very low temperatures

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2d
Sme Calculator1 mark

The homologous series of alkanes undergo combustion with oxygen.

 

A 2.0 dm3 flask contains 10.84 g of a gaseous alkane, X. The pressure in the flask is 300 kPa and the temperature is 20 oC.

 

Write an equation for the complete combustion of X.

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3a3 marks

Airbags are safety devices fitted to modern cars. They are designed to rapidly inflate in the event of a collision, in order to protect the occupants of the car from the effects of the impact, and then quickly deflate.

The inflation of an airbag depends on the chemical decomposition of sodium azide, NaN3.

The azide ion, N3–, contains one triple bond. Draw a ‘dot-and-cross’ diagram to show the arrangement of outer electrons present in an azide ion.

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3b3 marks

Suggest three properties of sodium azide. Explain your answer.

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3c5 marks

550 g of sodium azide, sodium hydroxide and ammonia were produced during the chemical reaction of sodium amide, NaNH2, and dinitrogen monoxide. The yield of sodium azide in this reaction was 95.0%.

 

Calculate the mass, in grams, of sodium amide required for this reaction.

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3d
Sme Calculator4 marks

In a serious collision, the airbag deploys and rapidly fills with nitrogen as sodium azide decomposes.

 

2NaN3 (s) → 2Na (s) + 3N2 (g)

 

Calculate the mass of sodium azide that must decompose in order to inflate an airbag to a volume of 7.50 × 10−2 m3 at a pressure of 150 kPa and temperature of 35 °C.

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3e
Sme Calculator5 marks

Sodium azide is toxic. It can be destroyed by reacting it with acidified nitrous acid, HNO2. 

 
i)
Balance the chemical equation for the reaction of sodium azide with acidified nitrous acid 
 
2NaN3 + ...HNO2 + ...HCl → ...N2 + ...NO + ...NaCl + 2H2O  
 
[2]
 
ii)
Calculate the volume of gas released, in dm3, when 250 cm3 volume of nitrous acid is used to destroy 75.0 g of sodium azide at room temperature and pressure.
 
[3]

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4a4 marks

This question is about the melting points of different chemicals.

The melting and boiling points of calcium and chlorine are given in Table 4.1.

 
Table 4.1
 

Element

Melting point / K

Boiling point / K

Chlorine

172

239

Calcium

1115

1757
 
i)
In terms of structure and bonding, compare the boiling points of chlorine and calcium.
 
[3]
 
ii)
Suggest why calcium is a liquid over a much greater temperature range than chlorine.
 
[1]

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4b5 marks

Sulfur dioxide and magnesium oxide are both oxides. The melting point of sulfur dioxide is –72 oC and the melting point of magnesium oxide is 2852 oC

 
i)
Explain, with reference to structure and bonding, the difference in the melting points of sulfur dioxide and magnesium oxide.
 
[3]
 
ii)
Ammonia has the same crystalline structure as sulfur dioxide but its melting point is 2 oC.
 
Explain the difference in melting point between sulfur dioxide and ammonia.
 
[2]

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4c5 marks

Silver chloride is used in photography films as well as having antiseptic properties. 

 
i)
Silver chloride has a structure similar to that of sodium chloride. Draw a diagram of the silver chloride lattice showing the arrangement of the ions.
 
[2]
 
ii)
Explain why silver chloride has a  relatively high melting point. You should refer to the difference between the electronegativities of the elements in your answer.
 
[3]

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4d1 mark

Diamond and ice are types of crystals.

 

Describe the structure and bonding present in both diamond and ice. Explain why the melting point of these two substances is very different. You should refer to the type of bonding present in both diamond and ice in your answer.

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5a3 marks

Mercury is a naturally occurring element that is a liquid at room temperature and pressure. Some of its physical properties are shown in Table 5.1.

 
Table 5.1
 
 

Appearance at room temperature

Melting
point / oC 

Boiling
point / oC 

Electrical conductivity

Mercury

shiny silver liquid

-38.8

356.7

good
 

Mercury can react with bromine to form mercury(II) bromide, HgBr2. 

 

Compare and explain the electrical conductivity of mercury and mercury(II) bromide.

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5b2 marks

The strength of ionic bonding in different compounds can be compared by using the amount of energy required to separate the ions, as shown in Table 5.2.

 
Table 5.2
 

Cation

Amount of energy required to separate the ions / kJ mol-1

LiF

1031

NaF

787

MgF2

2962
 

Using the data from Table 5.2, explain how changes in the cation affect the bond strength in an ionic compound.

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5c7 marks

Sodium chloride and iodine are both solids. Sodium chloride does not melt until it reaches a temperature of 1074 K yet iodine sublimes when heated gently, giving off purple vapours. Sodium chloride will conduct electricity when molten and iodine is a very poor conductor of electricity.

 
i)
State the type of crystal structure of iodine and sodium chloride.
 
[2]
 
ii)
Explain why iodine vaporises easily.
 
[2]
 
iii)
Explain the differences in electrical conductivity of sodium chloride and iodine.
 
[3]

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5d1 mark

Graphene, graphite and diamond are all forms of solid carbon.

 

Explain, in terms of structure and bonding, why graphene and graphite are good electrical conductors but diamond is a poor electrical conductor.

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1a6 marks

Carbon and silicon are elements in Group 14.
 

i)
Describe in simple terms the structure of solid C60.

[2]

ii)
C60 sublimes (turns directly from solid to gas) at approximately 800 K.

C60 (s) → C60 (g)

Diamond also sublimes but only above 3800 K.

Cdiamond (s) → C (g)

Explain why C60 and diamond sublime at such different temperatures.

[4]

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1b3 marks

C60 forms hydrocarbons with similar chemical properties to those of alkenes. One such hydrocarbon is C60H18.

i)
Define hydrocarbon.
[1]
ii)
C60H18 is an alkene.
State a test to indicate the presence of double bonds between carbon atoms in alkene molecules.

[1]

iii)
State the observations seen when the test in (b)(ii) is carried out on an alkene.  

[1]

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1c
Sme Calculator7 marks

0.144 g of C60 is placed in a 100 cm3 container of hydrogen gas at a temperature of 20 °C and a pressure of 1.00 × 105 Pa.

The container is heated to make the C60 and hydrogen gas react. The reaction occurs as shown in the equation.


C60(s) + xH2(g) → C60H2x(s)


After the reaction, the container is allowed to cool to 20 °C. The pressure decreases to 2.21 × 104 Pa. All of the C60 has reacted.

i)
Name the type of reaction that occurs.

[1]

ii)
Calculate the amount, in moles, of C60 that reacts.

amount of C60 = .................................................... mol [1]

iii)
Calculate the amount, in moles, of hydrogen gas that reacted with the C60.
Show your working.

amount of hydrogen gas = .................................................... mol [3]

iv)
Use your answers from (c)(ii) and (c)(iii) to deduce the molecular formula of the hydrocarbon, C60H2x.

(If you were unable to calculate the amount of hydrogen gas, assume that 0.00240 mol of hydrogen gas reacts. This is not the correct value.)
Show your working.


molecular formula = ........................................................... [2]

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1d3 marks

Silicon shows the same type of bonding and structure as diamond.

Silicon reacts with magnesium to form Mg2Si.

Solid Mg2Si reacts with dilute hydrochloric acid to form gaseous SiH4 and a solution of magnesium chloride.

i)
Construct an equation for this reaction. Include state symbols.

[2]

ii)
Predict the shape of the SiH4 molecule.

 [1]

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2a2 marks

Copper and iodine are both solids which have different physical and chemical properties.

Each element has the same face-centred crystal structure which is shown below.

crystal-structure

The particles present in such a crystal may be atoms, molecules, anions or cations. In the diagram above, the particles present are represented by the black balls. 

Which type of particles are present in the iodine crystal? Give their formula.

particle ....................................
formula ...................................

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2b2 marks

When separate samples of copper or iodine are heated to 50 °C, the copper remains as a solid while the iodine turns into a vapour.

Explain, in terms of the forces present in the solid structure, why copper remains a solid at 50 °C.

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2c2 marks

Explain, in terms of the forces present in the solid structure, why iodine turns into a vapour when heated to 50°C.

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2d
Sme Calculator4 marks

Calculate the volume, in cm3, that 5.00 g of iodine vapour occupies at 185 °C and 100 kPa.

The gas constant R = 8.31 J K–1 mol–1

Give your answer to 3 significant figures.

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2e2 marks

Although copper is a relatively unreactive metal, when it is heated to a high temperature in an excess of chlorine, copper(II) chloride is formed.

i)
How does chlorine behave in this reaction?

[1]
ii)
When a mixture of copper and iodine is heated to a high temperature, no reaction occurs.
Suggest a reason for this difference.
[1]

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3a4 marks

This question is about ideal gas theory. 

State the basic assumptions of the kinetic theory as applied to an ideal gas.

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3b1 mark

Carbon dioxide does not behave as an ideal gas. 


Suggest one reason why not. 

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3c2 marks

Explain why CO2 is a gas at room temperature.

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3d3 marks

Carbon dioxide can be used to inflate life jackets. 

Explain the effect of decreasing the temperature of carbon dioxide on the pressure inside a life jacket.

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4a4 marks

Until 1985, carbon was thought to exist in only two structural forms or allotropes. In 1985 another form, buckminsterfullerene, was discovered, in which the carbon exists as spherical molecules.

The other two forms of carbon have very different structures.

i)
Name these two forms.
[1]

ii)
Give three differences in physical properties between these two forms.
[3]

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4b2 marks

The diagram shows the structure of buckminsterfullerene.


1-4-4b-m-1-4-q4b-buckminsterfullerene
The molecule of buckminsterfullerene contains 60 carbon atoms.

Suggest a reason why buckminsterfullerene reacts with hydrogen under suitable conditions and give a formula for the product.

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4c
Sme Calculator3 marks

In 2010, two scientists from the University of Manchester were awarded the Nobel Prize for Physics for their work on graphene, a 'nano-material' and new structural form of carbon. 

i)
Graphene is in the form of sheets of carbon one atom thick.

Calculate the number of carbon atoms present in a sheet of graphene with a mass of one thousandth of a gram (0.001 g).
[1]

ii)
The number of hexagons in a large sheet of graphene can be assumed to be one half of the number of carbon atoms. Each hexagon has an area of 690 nm2

Calculate the area of the sheet of graphene in (i).


[2]

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4d2 marks

Explain whether you would expect samples of graphene and buckminsterfullerene to be electrical conductors.

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5a2 marks

The kinetic theory of gases is used to explain the large scale (macroscopic) properties of gases by considering how individual molecules behave.

State two basic assumptions of the kinetic theory as applied to an ideal gas.

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5b2 marks

State two conditions under which the behaviour of a real gas approaches that of an ideal gas.

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5c3 marks

Place the following gases in decreasing order of ideal behaviour.

ammonia, neon, nitrogen

most ideal .......................................................................................... least ideal

Explain your answer.

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5d2 marks

Explain why a liquid eventually becomes a gas as the temperature is increased.

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