Identification of Common Gases (AQA GCSE Chemistry: Combined Science)

Exam Questions

2 hours16 questions
1a1 mark

Indigestion tablets can be used to reduce the amount of acid in the stomach which can cause stomach pain and heartburn.

The active ingredient in many indigestion tablets is calcium carbonate such as the tablet in Figure 1.

Figure 1

aqa-gcse-8-2e-tq1a-indigestion-tablets

What word correctly describes products such as indigestion tablets?

Tick (✓) one box.

Compound  
Element  
Formulation  
Molecule  
1b1 mark

When indigestion tablets are added to an acid, what type of reaction will occur?

Circle the correct answer.

oxidation neutralisation decomposition

1c2 marks

Complete the word equation for the reaction between calcium carbonate and hydrochloric acid.

Choose words from the box below.

water calcium chloride calcium
oxygen hydrogen

 

calcium carbonate + hydrochloric acid → _________ + _________ + carbon dioxide

1d2 marks

The carbon dioxide produced in this reaction can be identified with a simple test using the equipment in Figure 2.

Figure 2

TXYIDP58_limewater-testChoose the correct word in each box to finish the sentences below.

  Solution A is

limewater.

limestone.

limewash.

  If carbon dioxide is present, solution A will

become blue.

produce bubbles.

turn cloudy.

1e
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2 marks

The indigestion tablets shown in Figure 1 contains calcium carbonate, CaCO3, as the active ingredient.

Calculate the relative formula mass (Mr) of calcium carbonate.

Relative atomic masses:   Ca = 40;  C = 12;  O = 16

Relative formula mass = ____________________

1f
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2 marks

Calculate the percentage by mass of calcium in calcium carbonate, CaCO3.

Use your answer from part (e) and the equation below.

Percentage space mass space of space element space equals space fraction numerator straight A subscript straight r space cross times space number space of space atoms space of space the space element over denominator straight M subscript straight r space of space the space compound end fraction space cross times space 100

Percentage by mass of calcium = _____________________ %

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2a2 marks

Hydrogen peroxide, H2O2, has a wide range of uses including cleaning products and hair dyes.

It decomposes to give water and oxygen.

Complete the balanced symbol equation for the reaction.

____ H2O2   →   ____ H2O   +   ________

2b2 marks

The presence of oxygen can be confirmed by a test.

Circle one word from each box to complete the sentences.

  The test for oxygen gas is to use  

limewater.

a lit splint.

a glowing splint.

  If oxygen gas is present, this will

relight.

make a pop.

turn cloudy.

2c1 mark

Describe what you see happening when oxygen gas is given off.

2d2 marks

The decomposition of hydrogen peroxide can be catalysed by the use of manganese (IV) oxide.

Complete the sentences using the words from the box below.

increases decreases remains the same

When manganese (IV) oxide is added to hydrogen peroxide, the rate at which oxygen is produced ____________________.

The total amount of oxygen produced ____________________.

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3a1 mark

A student investigates the reaction between dilute hydrochloric acid and the metals magnesium, iron and zinc.

The method they used is given below and the apparatus is shown in Figure 1

  • Using a small measuring cylinder, add 5 cm3 of dilute hydrochloric acid to each of three test tubes
  • Add about 1 cm length of magnesium ribbon to the first tube
  • Use a lighted splint to test for any gases given off
  • Repeat using a few pieces of iron filings in the second test tube and then some zinc turnings in the third test tube

They recorded their observations after adding the metal.

Figure 1

metals--hcl

Circle one word / phrase in each box to complete the sentences.

  The gas being tested for is

oxygen.

hydrogen.

chlorine.

  A positive test for this gas is

the flame will glow brighter.

the flame will go out.

a squeaky pop will be heard.

3b1 mark

In the reaction between magnesium and hydrochloric acid, the salt, magnesium chloride is produced.

What is the correct formula for magnesium chloride?

Tick (✓) one box.

MgCl  
MgCl2  
Mg2Cl  
Mg2Cl2  
3c1 mark

Why would the method that the student used in part (a) not be a fair test?

3d2 marks

The student altered the method so that it was a fair test.

Some of the observations the student made are shown in Table 1.

Table 1

Metal Observations
Magnesium  Dissolves quickly, gets hot, bubbles quickly released, colourless solution left
Iron Very slow bubbling
Zinc Bubbles given off, metal slowly dissolves


Use the results in Table 1 to determine the order of reactivity of metals, starting with the least reactive.

Least reactive ____________________
  ____________________
Most reactive ____________________
3e1 mark

Suggest what you would observe if the experiment was repeated using copper filings.

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4a1 mark

The electrolysis of sodium chloride solution is industrially very important as it provides the raw materials for many other products, such as bleach, soap and paper.

The apparatus shown in Figure 1 can be used to investigate this electrolysis in the laboratory.

Figure 1

electrolysis-nacl-solution

What is gas A?

Tick (✓) one box.

Oxygen  
Hydrogen  
Sodium   
4b2 marks

The presence of chlorine gas can be tested.

Describe a test that would identify chlorine gas.

Give the result of the test.

Test ___________________________________________
Result ___________________________________________
4c1 mark

The solution around the negative electrode became alkaline.

What ion is responsible for the solution becoming alkaline?

Tick (✓) one box.

H+  
H-  
OH+  
OH-  
4d2 marks

When molten sodium chloride undergoes electrolysis, what products are formed at each electrode?

Circle to correct answer to complete the sentences.

  At the positive electrode, the substance produced is

sodium

chlorine.

oxygen.

hydrogen.

 
At the negative electrode, the substance produced is

sodium

chlorine.

oxygen.

hydrogen.

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1a3 marks

Limestone is used as a building material even though it is eroded by acid rain.

Limestone contains the compound calcium carbonate which reacts with hydrochloric acid as shown.

CaCO3 (s) + 2HCl (aq) → CaCl2 (aq) + H2O (l) + CO2 (g)

Describe a test to show that CO2 is produced in the reaction.

1b3 marks

Gases expelled from the exhausts of vehicles produce sulfuric acid and nitric acid.

  • A student investigated the reaction of both acids with limestone.
  • Only the type of acid was changed, all other variables in the investigation were kept the same. 
  • The student measured the volume of CO2 gas produced every minute for a total of 10 minutes. 
  • The first reaction studied was between dilute sulfuric acid and a cube of calcium carbonate.
  • The student then repeated the experiment using dilute nitric acid. 

The results are shown in Figure 1.

Figure 1

8-2-identification-of-common-gases-medium-q1b

State three variables that must be kept the same for this investigation.

1c4 marks

Different results were obtained for reacting calcium carbonate with sulfuric acid than with nitric acid.

The equations for both reactions are shown below.

CaCO3 (s) + H2SO4 (aq) → CaSO4 (s) + H2O (l) + CO2 (g)

CaCO3 (s) + 2HNO3 (aq) → Ca(NO3)2 (aq) + H2O (l) + CO2 (g)

Describe how the results for sulfuric acid are different and explain this difference with reference to the symbol equations.

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21 mark

During the electrolysis of brine, chlorine gas forms at one electrode.

2Cl- (aq) rightwards arrowCl2 (g) + 2e-

Which test would be most appropriate to confirm that chlorine gas was produced?

  • Collect the gas and see if it extinguishes a glowing splint

  • Collect the gas and check if it is green

  • Collect the gas and see if it bleaches damp litmus paper

  • Collect the gas and check if it smells of swimming pools

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31 mark

Which is the correct method for testing for hydrogen gas?

  • Hold the tube containing the gas upright and place a lit splint at the end of the tube

  • Hold the tube containing the gas upright and place a glowing splint at the end of the tube

  • Hold the tube containing the gas angled down and place a lit splint at the end of the tube

  • Hold the tube containing the gas angled down and place a glowing splint at the end of the tube

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4a3 marks

A fungicide suitable for crops contains copper sulfate, CuSO4, and ammonium carbonate, (NH4)2CO3.         

A student tested a sample of the fungicide.

Hydrochloric acid was added and a gas was produced that turned limewater milky.

Complete the sentences. 

The gas produced was _________________________ which shows that _________________________ ions are in the mixture. 

The formula for the ion is: ________

4b4 marks

Describe a method for testing the carbon dioxide gas produced from the reaction of ammonium carbonate, (NH4)2CO3 and hydrochloric acid, HCl.

You may use a diagram.

 
4c2 marks

Next, sodium hydroxide solution was added to a sample of the fungicide.

A gas was produced indicating that ammonia was produced.

Ammonia can react with chlorine gas to form hydrochloric acid and then ammonium chloride, a white powder. These are not the desirable products.

Describe how the gas in the reaction vessel could be tested in order to check for the presence of chlorine. 

Complete the sentence. 

The gas in the vessel could be tested using damp ____________________ which turns _____________________ if chlorine gas is present.

4d1 mark

Chlorine gas also has a distinctive smell, like the smell of swimming pools and bleach.

Why should this not be used as a test to identify the gas?

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5a1 mark

Methane, CH4 contains the elements carbon and hydrogen only.

A student wanted to find out which new substances are produced when methane is burned.

The student set up the apparatus shown below.

aqa-gcse-8-2m-tq3a-products-of-combustion

Which gas in the air reacts with methane when it burns?
 
5b1 mark

Name the liquid collected.

5c1 mark

Name the gas which turns limewater milky.

5d2 marks

When methane burns an exothermic reaction takes place.

What is meant by an exothermic reaction?

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6a3 marks

Hydrogen peroxide, H2O2, is often used as a bleach. It decomposes forming water and oxygen.

Write the balanced chemical equation for the decomposition of hydrogen peroxide.

6b2 marks

Give a test for oxygen. 

Test: _________________________

 Result of test: _________________________

6c2 marks

Describe the test for hydrogen. 

Test: _________________________ 

Result of test: _________________________

6d2 marks

Two experiments were carried out to test if the mass of a manganese dioxide catalyst, MnO2, affected the rate at which the hydrogen peroxide decomposed.

Complete Figure 1 to show how you could measure the volume of oxygen formed during the decomposition.

Figure 1

aqa-gcse-8-2m-tq4d-mg--hydrogen-peroxide

6e2 marks

The same volume and concentration of hydrogen peroxide solution was used for both experiments.

What two other factors must be kept the same to make it a fair test?

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71 mark

Which is not true about the test for carbon dioxide gas?

  • The gas is bubbled through limewater solution

  • Limewater is calcium hydroxide solution

  • The solution will turn cloudy due to the formation of a white precipitate

  • The colour will fade after a few minutes

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81 mark

The electrolysis of fresh water produces hydrogen gas and oxygen gas.

The electrolysis of salt water (brine) produces hydrogen gas and chlorine, and leaves a solution of sodium hydroxide.

Which test would not help to identify a sample as being fresh water or salt water?

  • A gas collected makes a 'squeaky pop' when a lit splint is held in it

  • A gas collected relights a glowing splint

  • A gas collected bleaches damp litmus paper

  • The pH of the solution increases

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1a2 marks

Sodium hydrogencarbonate, NaHCO3, is an alkali that undergoes a neutralisation reaction with sulfuric acid, H2SO4.

Write the balanced symbol equation for this reaction.

1b2 marks

One of the active ingredients in baking powder is sodium hydrogencarbonate. It also contains an acid.

When water is added to baking powder, carbon dioxide is released.

Outline how you could test to confirm the presence of carbon dioxide.

1c2 marks

Sodium hydrogencarbonate is also used in indigestion tablets.

Indigestion is caused by excess hydrochloric acid in the stomach.

A side effect of taking indigestion tablets can be a build up of gas in the stomach which causes stomach pain and bloating

Explain why.

1d
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2 marks

A student made a solution of 42 g/dm3 sodium hydrogencarbonate .

What mass of sodium hydrogencarbonate needs to be added to 250 cm3 of distilled water to obtain this concentration?

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2a1 mark

A student investigated photosynthesis of algae by placing some algae in water with a light shining onto the algae.

The water contained a dissolved gas necessary for photosynthesis to occur.

Name the dissolved gas.

2b2 marks

As photosynthesis occurred, gas bubbles were seen and the resulting gas was collected.

Describe a test that could be performed to identify the gas collected.

Give the results of the test.

2c3 marks

The student increased the light intensity which was shining on the beaker containing algae and water.

How would the observations the student would make be different after increasing the light intensity?

Explain your answer.

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3a1 mark

A student investigated how the volume of gases produced changed with time during the electrolysis of sodium chloride solution.

Figure 1 shows the equipment the student used.

Figure 1

electrolysis-sodium-chloride-solution

Why is hydrogen gas, not sodium, collected at the cathode?

3b2 marks

Chlorine gas is collected at the anode.

Write the half equation for the reaction at the anode.

3c2 marks

Describe a test for chlorine gas.

Give the result of the test if chlorine is present.

3d1 mark

The student recorded the results shown in Table 1.

Table 1

Volume of gas collected in cm3
Time in minutes Hydrogen Chlorine
0 0.0 0.0
4 1.8 0.2
8 3.6 1.1
12 5.4 2.9
16 7.2 4.8

The volume of chlorine collected at the anode is expected to be the same as the volume of hydrogen collected at the cathode.

Suggest why the volume of gas collected at each electrode is not the same.

Assume no gas has escaped from the apparatus.

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4a4 marks

A student investigated how the rate of reaction between magnesium and hydrochloric acid changed with temperature, shown in Figure 1.

The student measured the time for the magnesium to stop reacting.

Figure 1

aqa-gcse-8-2h-tq4a-magnesium--hcl

The equation for the reaction is:

Mg(s) + 2HCl(aq)    MgCl2(aq)  +  H2(g)

Describe a test for hydrogen gas.

Give the result of the test if hydrogen is present and given the balanced symbol equation for the reaction that occurs if hydrogen is present.

4b4 marks

State and explain what would happen to the rate of reaction between magnesium and hydrochloric acid as the temperature increased.

4c5 marks

2.0 g of magnesium reacted with a solution containing 0.025 moles of hydrochloric acid.

Calculate the mass of hydrogen gas that you would expect to be produced in this reaction.

4d3 marks

The student repeated the experiment but used a white powder, compound X, instead of magnesium.

A gas was produced during the reaction with hydrochloric acid. When the gas was bubbled through turned limewater, it turned cloudy.

The student carried out a further chemical test on compound X which confirmed the presence of potassium ions.

Give the formula of compound X.

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