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6 (a) Sodium thiosulfate solution, Na2S2O3, reacts with dilute hydrochloric acid - Edexcel - GCSE Chemistry - Question 6 - 2020 - Paper 1
Question 6
6 (a) Sodium thiosulfate solution, Na2S2O3, reacts with dilute hydrochloric acid. Na2S2O3(aq) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + SO2(g) + S(s) (i) When dilute hydro... show full transcript
Worked Solution & Example Answer:6 (a) Sodium thiosulfate solution, Na2S2O3, reacts with dilute hydrochloric acid - Edexcel - GCSE Chemistry - Question 6 - 2020 - Paper 1
Step 1
Explain why the mixture turns cloudy.
Answer
The mixture turns cloudy due to the formation of sulfur precipitate ( S(s)) when sodium thiosulfate reacts with dilute hydrochloric acid. During the reaction, sulfur dioxide is produced along with sulfur itself. The sulfur precipitate scatters light, resulting in the mixture appearing cloudy.
Step 2
Describe how the rate at which the mixture goes cloudy can be measured.
Answer
The rate at which the mixture goes cloudy can be measured by timing how long it takes for a marked cross or an object to become obscured when viewed through the solution. Alternatively, one can measure the time taken for the reaction to reach a certain opacity using a light sensor or by recording the decrease in light transmission through the solution.