This question is about sodium chloride - AQA - GCSE Chemistry - Question 6 - 2017 - Paper 1
Question 6
This question is about sodium chloride.
A student reacted hydrochloric acid and sodium hydroxide solution to produce sodium chloride solution.
The student:
• measu... show full transcript
Worked Solution & Example Answer:This question is about sodium chloride - AQA - GCSE Chemistry - Question 6 - 2017 - Paper 1
Step 1
6 (a) (i) Suggest one reason why the temperature change could be greater than expected.
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Answer
The initial temperature reading was too low.
Step 2
6 (a) (ii) What conclusion can you make about the reaction from the results in Table 2?
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Answer
The reaction is exothermic as indicated by the increase in temperature from the initial readings to the highest temperatures recorded. This suggests that the reaction between hydrochloric acid and sodium hydroxide releases heat during the neutralization process.
Step 3
6 (b) (i) Explain what happens at the negative electrode and why sodium is not produced.
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At the negative electrode (cathode), positive ions gain electrons, which means hydrogen ions (from the acid) are reduced to form hydrogen gas. Sodium ions are not reduced because sodium is below hydrogen in the reactivity series, making it less reactive and not able to discharge in this process.
Step 4
6 (b) (ii) Complete the half equation.
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2 Cl⁻ → Cl₂ + 2 e⁻
Step 5
6 (b) (iii) Explain why the pH of the solution after electrolysis was 14.
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Answer
After electrolysis, the solution becomes alkaline due to the production of sodium hydroxide, which increases the concentration of hydroxide ions (OH⁻) in the solution, resulting in a pH of 14.
