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
The hydrochloric acid and sodium hydroxide solution were the same concentration. 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
The student did the investigation three times. What conclusion can you make about the reaction from the results in Table 2?
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Answer
The results indicate that the reaction between hydrochloric acid and sodium hydroxide is exothermic because the highest temperatures recorded were consistently higher than the initial temperatures, demonstrating a release of heat.
Step 3
Explain what happens at the negative electrode and why sodium is not produced.
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At the negative electrode (cathode), positive hydrogen ions gain electrons to form hydrogen gas. Sodium is not produced because it is more reactive than hydrogen, and hydrogen ions are preferentially reduced.
Step 4
Chlorine gas is produced at the positive electrode. Complete the half equation.
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Answer
2 Cl⁻ → Cl₂ + 2 e⁻
Step 5
Explain why the pH of the solution after electrolysis was 14.
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Answer
After electrolysis, the solution becomes alkaline because sodium hydroxide (NaOH) is produced, increasing the concentration of hydroxide ions (OH⁻) in the solution, which results in a high pH value of 14.
