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Sodium thiosulfate solution, Na₂S₂O₃, reacts with dilute hydrochloric acid - Edexcel - GCSE Chemistry Combined Science - Question 3 - 2020 - Paper 1
Question 3
Sodium thiosulfate solution, Na₂S₂O₃, reacts with dilute hydrochloric acid. Na₂S₂O₃(aq) + 2HCl(aq) → 2NaCl(aq) + H₂O(l) + SO₂(g) + S(s) (i) When dilute hydrochlori... show full transcript
Worked Solution & Example Answer:Sodium thiosulfate solution, Na₂S₂O₃, reacts with dilute hydrochloric acid - Edexcel - GCSE Chemistry Combined Science - Question 3 - 2020 - Paper 1
Step 1
Explain why the mixture turns cloudy.
Answer
The mixture turns cloudy due to the formation of sulfur precipitate. When sodium thiosulfate reacts with hydrochloric acid, sulfur is produced as a solid. This solid forms small particles that disperse in the solution, scattering light and resulting in a cloudy appearance.
Step 2
Describe how the rate at which the mixture goes cloudy can be measured.
Answer
The rate of the cloudiness can be measured by timing how long it takes for a marked cross (or any visible object) to become obscured when viewed through the solution. A stopwatch can be used to measure the time taken, and different concentrations of hydrochloric acid can be tested to compare the speeds of cloudiness formation.