In the electrochemical cell below, carbon electrodes are used during the electrolysis of a concentrated sodium chloride solution - NSC Physical Sciences - Question 9 - 2016 - Paper 2
Question 9
In the electrochemical cell below, carbon electrodes are used during the electrolysis of a concentrated sodium chloride solution.
Gas X Gas Y
Electrode P ... show full transcript
Worked Solution & Example Answer:In the electrochemical cell below, carbon electrodes are used during the electrolysis of a concentrated sodium chloride solution - NSC Physical Sciences - Question 9 - 2016 - Paper 2
Step 1
9.1 Is the reaction EXOTHERMIC or ENDOTHERMIC?
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Answer
The reaction is ENDOTHERMIC. This is because the process of electrolysis requires an input of energy to drive the non-spontaneous reaction.
Step 2
9.2 Is electrode P the ANODE or the CATHODE? Give a reason for the answer.
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Electrode P is the ANODE. This is because the anode is connected to the positive terminal of the battery, where oxidation occurs.
Step 3
9.3.1 NAME or FORMULA of gas X
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Gas X is Chlorine (Cl2).
Step 4
9.3.2 NAME or FORMULA of gas Y
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Gas Y is Hydrogen (H2).
Step 5
9.3.3 Reduction half-reaction
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The reduction half-reaction is:
2H2O(l)+2e−→H2(g)+2OH−(aq)
Step 6
9.4 Is the solution in the cell ACIDIC or ALKALINE (BASIC) after completion of the reaction? Give a reason for the answer.
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The solution is ALKALINE (BASIC) after completion of the reaction. This is because hydroxide ions (OH⁻) are produced during the electrolysis process, leading to an increase in the pH.
