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Question 1
This question is about hydrogen fuel cells in cars. |
a) | In a fuel cell, hydrogen (H2) reacts with oxygen (O2) to form water. Write a balanced chemical equation for this reaction.
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b) | Suggest one advantage and one disadvantage of using fuel cells instead of petrol.
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c) | The reaction profile below shows the reaction between hydrogen and oxygen. State what each letter represents on the reaction profile.
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Question 2
This question is about the operation of a hydrogen fuel cell. |
a) | The electrodes of a fuel cell are in contact with water and air. The electrodes are made from platinum rather than iron. Explain why iron is not a suitable metal for the electrodes of the cell.
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b) | The diagram below shows a simple hydrogen fuel cell. Explain how the hydrogen fuel cells works. In your answer you should include:
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c) | State one disadvantage of using hydrogen fuel cells in vehicles.
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Question 3
This question is about the hydrogen fuel cell. |
a) | Which of the following represents the equation that takes place at the anode? A 2H2(g) + O2(g) âž” 2H2O(g) B 4H+(aq) + 4e- âž” 2H2(g) C 2H2(g) âž” 4H+(aq) + 4e- D 4H+(aq) + O2(g) + 4e- âž” 2H2O(g)
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b) | What happens to hydrogen when it enters the fuel cell? A it is reduced B it is neutralised C it is oxidised D it is diluted
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c) | The diagram below shows the reaction profile between hydrogen and oxygen in the hydrogen fuel cell. Explain with reference to the reaction profile above whether the reaction is endothermic or exothermic.
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Question 4
A student is investigating chemical cells. The diagram below shows the students equipment. |
a) | The student replaces electrode B with different metals and records the value shown by the voltmeter. The table below shows the results. State two variables that should be controlled for this experiment.
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b) | State which metal in the table above is the most reactive and give a reason for your answer.
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c) | When the electrode is replaced with silver, the reading is negative. Explain why.
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Question 5
This question is about chemical cells. |
a) | A student places two copper electrodes into a beaker of sodium chloride solution. The electrodes are then connected to a voltmeter. Explain what the student would observe.
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b) | The student then replaces the electrodes with various metals and records the results in a table. The table of results in below. Which two metals give the highest difference in reactivity?
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c) | Rank the metals in the table above in order of reactivity.
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d) | Zinc is oxidised at the electrode. Write a balanced equation to show the oxidation of zinc to form Zn2+.
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e) | Electrolysis and chemical cells both involve chemical reactions and electricity. State, in terms of electricity and chemical reactions, how the two processes can be considered opposite.
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Question 6
This question is about chemical cells and rechargeable batteries. |
a) | Explain the difference between the term cell and battery.
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b) | Explain why alkaline batteries eventually stop working.
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c) | Some batteries are rechargeable. Explain how the reaction that takes place in a rechargeable battery is different to that in an alkaline battery.
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Question 7
This question is about the hydrogen fuel cell. |
a) | When hydrogen enters the fuel cell it becomes oxidised. Explain what is meant by the term oxidised.
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b) | Explain what happens to the hydrogen in the fuel cell after it has become oxidised.
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c) | Write a half equation for the reaction between hydrogen and oxygen at the cathode.
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d) | The reaction between hydrogen and oxygen in the fuel cell is exothermic. Draw a reaction profile to show this reaction. On your sketch you should label the activation energy and the overall energy change.
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