Amount of Substance & Gas Volume (AQA GCSE Chemistry)

Exam Questions

2 hours24 questions
1a2 marks

This question is about gas volumes.

What volume does one mole of any gas occupy at room temperature and pressure?

 

Give your answer in cm3 and dm3.

1b2 marks

What are the temperature and pressure implied with room temperature and pressure?

 
Room temperature = __________ oC
 
Room pressure = __________ atm
1c1 mark

State one equation to calculate the amount of gas in moles.

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2a2 marks

Ethanol, C2H5OH, undergoes complete combustion to form carbon dioxide and water.

Complete the balanced symbol equation for the complete combustion of ethanol.

 ___ C2H5OH + ___ O2 → ___ CO2 + ___ H2O

2b1 mark

Which of the chemicals in the reaction equation are gases at room temperature and pressure? 

2c
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2 marks
The complete combustion of ethanol is performed at room temperature and pressure.

 

Draw a circle around the correct word to complete the sentences.

 

9 moles of oxygen produce

2 moles

3 moles 

6 moles

9 moles

of carbon dioxide.

 

A volume of 

24 dm3 

72 dm3

144 dm3 

24000 cm3

of carbon dioxide is released.

 

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3a
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1 mark

0.0625 moles of methane is burnt in air according to the following equation:

CH4 + 2O2 → CO2 + 2H2O

How many moles of oxygen are required for this combustion reaction?

 

Tick (one box. 

0.03125  
0.0625  
0.125  
3b
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2 marks

If the reaction is completed at room temperature and pressure, what volume, in dm3, of methane is being burned?

3c
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1 mark

If the reaction was completed at room temperature and pressure, what volume, in dm3, of carbon dioxide is produced?

3d
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1 mark

Assuming that all the chemicals involved in the reaction are in the gaseous state, the balanced symbol equation is:

CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (g)

Draw a circle around the correct answer to complete the sentence.

 

Burning 2500 cm3 of methane produces a total volume of 

2500 cm3 

5000 cm3 

7500 cm3 

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4a1 mark

Helium is a gas at room temperature and pressure.

Calculate the number of moles in a 38.4 g sample of helium.

 

Relative atomic mass (Ar):     He = 4

Use the equation: 

begin mathsize 14px style Moles equals mass over A subscript straight r end style

4b
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2 marks

What volume of gas, in cm3 and dm3, does 38.4 g of helium occupy?

4c
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2 marks

Chlorine, Cl2, is a gas at room temperature and pressure.

Calculate the number of moles in a 376.3 g sample of chlorine. 

Relative atomic mass (Ar):     Cl= 35.5 

Use the equation: 

begin mathsize 14px style Moles equals mass over M subscript straight r end style

4d
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2 marks

What volume of gas, in cm3 and dm3, does 376.3 g of chlorine occupy?

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5a
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2 marks

Carbon dioxide and water are formed when propane undergoes complete combustion.

The equation for the reaction is:

C3H8 (g) + 5 O2 (g) → 3 CO2 (g) + 4 H2O (l)

Calculate the number of moles in 55.44 g of propane.

 Relative molecular mass (Mr):     C3H8 = 44

5b
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1 mark

What volume of gas, in dm3, does 55.44 g of propane occupy?

5c
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1 mark

What volume of carbon dioxide is produced when 55.44 g undergoes complete combustion?

5d
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3 marks

In another combustion experiment, 1.3 dm3 of propane is combusted in the presence of 8.0 dm3 of oxygen.

Calculate the volume of oxygen that is left unreacted.

 

Give your answer in cm3.

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1a2 marks

Nitrogen and hydrogen react together in the Haber process to produce ammonia.

Figure 1 shows a flow diagram for the process

Figure 1

aqa-gcse-sq-3-5-1a-haber-process-flowchart

A gaseous mixture of NH3, N2 and H2 leaves the reactor where the ammonia is separated and the hydrogen and nitrogen are recycled back into the reactor. The reactor has a temperature of 450 oC and a pressure of 200 atmospheres.

What does Avogadro's Law state about all three gases?

1b2 marks

The gases have the following boiling points:

Gas Boiling Point (oC)
Ammonia -33
Nitrogen -196
Hydrogen -253


Suggest how ammonia can be separated from the other gases. 

1c2 marks

The equation for the Haber process is:

N2 (g)  +  3H2 (g)  ⇌  2NH3 (g)

Calculate the volume of ammonia produced from the complete reaction of 795 dm 3 of hydrogen.

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2a2 marks

A student investigated the electrolysis of a solution of sodium chloride by measuring how the volume of gases produced changes with time.

Figure 1 shows the apparatus used in the investigation.

 

Figure 1

aqa-gcse-sq-3-5-2a-electrolysis-of-sodium-chloride

The student made an error in designing and setting up the apparatus for this investigation.

Identify the error and suggest what needs to be changed.

2b3 marks

The student soon adjusted the apparatus and was able to perform the investigation correctly. 

The student measured the volumes of gases produced every minute for 20 minutes and constructed a graph of these results.

Figure 2 shows the graph of the investigation.

Figure 2

8y~NW0iQ_4

Using the graph, describe the trends shown in the results.

2c1 mark

The number of moles of each gas produced at each electrode is the same and no gas escapes from the apparatus however there is a difference in the amount of gas collected.

Suggest one reason for the difference in volume of each gas collected.

2d4 marks

Using Figure 2, calculate the amount in moles of chlorine collected after 16 minutes.

The volume of one mole of any gas at room temperature and pressure is 24.0 dm3

State your answer in standard form.

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3
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1 mark

What is the volume occupied by 5.6 g of nitrogen gas at RTP?

Relative atomic masses (Ar): N= 14

  • 2.4 dm3

  • 4.8 dm3

  • 9.6 dm3

  • 12 dm3

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4a4 marks

This question is about calculating the volumes of gases produced in different reactions.

What volume of hydrogen is produced from the reaction of 2.5 g of magnesium with excess sulfuric acid?

Mg   +   H2SO4  →   MgSO4  +   H2 

Relative atomic mass (Ar): Mg = 24

4b4 marks

What volume of steam is produced from the combustion of 2.000 kg of methane in excess oxygen?

CH4    +    2O2     →    CO2     +     2H2O 

Relative formula mass (Mr): CH4 = 16

4c5 marks

What mass of iodine is required to react with hydrogen to produce 67.20 dm3 of hydrogen iodide?

I2    +    H2     →    2 HI

Relative atomic mass (Ar): I = 127

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5
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1 mark

The reaction between nitrogen and hydrogen produces ammonia.

N2 (g) + 3H2 (g) begin mathsize 14px style rightwards harpoon over leftwards harpoon end style  2NH3 (g)

What volume of ammonia is produced from 565 cm3 of hydrogen?

  • 1130 cm3

  • 377 cm3

  • 283 cm3

  • 847 cm3

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6
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1 mark

A gas cylinder has a volume of 264 dm3.   

What mass of hydrogen does it contain?

Relative atomic masses (Ar): H=1

  • 22 g

  • 11 g

  • 24 g

  • 264 g

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7a5 marks

Air bags are designed to protect car passengers in the event of an accident. 

Crash sensors in the car detect an impact and immediately heat a small container with a mixture of chemicals. 

The heat produced triggers a chemical reaction which produces nitrogen gas. 

The gas fills the bag which provides the cushion needed for protection.

Figure 1 demonstrates this process.

 
Figure 1
aqa-gcse-sq-3-5-3a-airbag

The chemical mix contains sodium azide (NaN3) which undergoes thermal decomposition to form sodium and nitrogen.

The equation for the reaction is:

2NaN3       →       2Na       +       3N2

A typical air bag contains around 143 g of sodium azide.

Calculate the mass of nitrogen produced when 143 g of sodium azide decomposes.

Relative atomic masses (Ar): N = 14; Na = 23

7b1 mark

1 g of nitrogen has a volume of 0.86 litres at room temperature and pressure.

What volume of nitrogen would be produced from 143 g of sodium azide?

(If you did not answer part (a), assume that the mass of nitrogen produced from 143 g of sodium azide is 85 g. This is not the correct answer to part a))

7c2 marks

State the conditions of temperature and pressure at r.t.p.

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1a3 marks

This question is about electrolysis.

In the electrolysis of molten potassium bromide, separate reactions occur at the electrodes.

Write two balanced half equations for the reactions that occur at the anode and the cathode.

1b
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3 marks

During the electrolysis of molten potassium bromide, 3.12 g of potassium was formed. 

Calculate the number of moles of bromine formed in the reaction. 

Relative atomic masses (Ar):     K = 39,     Br = 80

1c
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2 marks

11.3% of the bromine produced in the reaction escapes the container. 

Calculate the volume, in dm3, of bromine in the container.

1d
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3 marks

When molten sodium chloride was electrolysed, 0.28 g of sodium was formed at one electrode. 

Calculate the volume of gas, in cm3, that was produced at room temperature and pressure. 

Relative atomic masses (Ar):     Na = 23,     Cl = 35.5

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2a3 marks

This question is about combustion.

A 0.050 mol sample of a hydrocarbon was burned in excess oxygen.

To determine the identity of the hydrocarbon, the type of combustion used is important.

Which type of combustion should be used to determine the identity of the hydrocarbon? Explain your reasoning.

2b
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1 mark

3.6 dm3 of carbon dioxide were produced during the complete combustion of the 0.050 mol sample of a hydrocarbon.

Calculate the number of moles of carbon dioxide released.

2c
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2 marks

When the hydrocarbon was burned 1.204 x 1023 molecules of water were produced. 

Calculate the number of moles of hydrogen atoms in 1.204 x 1023 molecules of water.

2d
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3 marks

The amount of hydrocarbon burned was 0.050 mol.

Calculate the molecular formula of the hydrocarbon.

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3a2 marks

Sodium carbonate reacts with dilute hydrochloric acid:

Na2CO3 + 2HCl → 2NaCl + H2O + CO2

A student investigated the volume of carbon dioxide produced when different masses of sodium carbonate were reacted with dilute hydrochloric acid.

This is the method used.

  1. Place a known mass of sodium carbonate in a conical flask.
  2. Measure 10 cm3 of dilute hydrochloric acid using a measuring cylinder.
  3. Pour the acid into the conical flask.
  4. Place a bung in the flask and collect the gas until the reaction is complete.

The student has set the apparatus incorrectly as shown in Figure 1.

Figure 1

aqa-gcse-3-5h-q3a-gas-collection-apparatus-error

Identify the error and describe what would happen if the student used the apparatus.

3b1 mark

The student corrected the error and collected the results shown in Table 1.

Table 1

Mass of sodium carbonate in g 0.07 0.12 0.23 0.29 0.34 0.54 0.59 0.65
Volume of carbon dioxide gas in cm3 16.0 27.5 52.0 65.0 77.0 95.0 95.0 95.0

Suggest why the volume of carbon dioxide collected reaches a maximum of 95.0 cm3.

3c3 marks

Describe how the student could accurately determine the minimum mass of sodium carbonate required to produce 95.0 cm3 of carbon dioxide.

3d
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3 marks

The carbon dioxide was collected at room temperature and pressure. 

Calculate the number of atoms of oxygen present in the 95.0 cm3 of carbon dioxide produced. 

Give your answer to three significant figures.

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4
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1 mark

Air bags contain sodium azide (NaN3) which decomposes on heating to form sodium and nitrogen.

2NaN3       →       2Na       +       3N2

What volume of nitrogen would be produced from 13 g of sodium azide?

Relative atomic mass (Ar): N = 14

Relative formula mass (Mr): NaN3 = 65

  • 4.8 dm3

  • 7.2 dm3

  • 48 dm3

  • 72 dm3

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5a3 marks

This question is about power stations.

Coal-fired power stations are being phased out as the supply of coal decreases and greater restrictions on emissions are implemented.

Coal typically contains between 0.2% and 5% sulfur by dry weight.

Calculate the average number of moles of sulfur in 75 tonnes of coal. 

Relative atomic mass (Ar):     S = 32

1 tonne = 1 x 106 g

5b
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2 marks

Calculate the volume of sulfur dioxide released from the combustion of 75 tonnes of typical coal.

5c
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3 marks

Natural gas is replacing coal in some power stations. 

The typical sulphur content of natural gas is 5.5 x 106 g / dm3

An articulated fuel tanker truck can carry up to 36000 dm3 of natural gas. 

Calculate the volume, in cm3, of sulfur dioxide that could be released by combusting the 36000 dm3 of natural gas carried in the tanker truck.

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6
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1 mark

Hydrogen can be produced by reacting methane with steam: 

CH4 + H2O  → CO + 3H2

What volume would the products occupy at RTP after reacting 32 g of methane with excess steam?  

Relative atomic masses (Ar):  C = 12    H = 1    O = 16

  • 24 dm3

  • 72 dm3

  • 96 dm3

  • 192 dm3

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7a2 marks

This question is about the reduction of tungsten oxide, WO3.

A teacher reduces tungsten oxide to tungsten using the following method and the equipment shown in Figure 1.

  • Record the mass of the weighing boat
  • Add tungsten oxide and record the mass again
  • Heat the weighing boat and tungsten oxide strongly for two minutes and then allow to cool
  • Record the mass of the weighing boat and its contents

Figure 1

aqa-gcse-sq-3-5h-4a-tungsten-oxide-reduction

Write the balanced symbol equation, including state symbols, for the reduction of tungsten oxide by hydrogen.

7b1 mark

State one addition to the method to check that the tungsten oxide has been completely reduced.

7c
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4 marks

In industry, tungsten oxide is reduced on a large scale using hydrogen.

Using your equation from part (a), calculate the minimum volume, in dm3, of hydrogen that is required to react with 13.92 tonnes of tungsten oxide. 

Relative atomic masses (Ar):     W = 184,     O = 16,     H = 1 

1 tonne = 1 x 106 g

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