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For kinetic study of the reaction of iodine ion with H2O2 at room temperature : (a) Always use freshly prepared starch solution. (b) Always keep the concentration of sodium thiosulphate solution less than that of KI solution. (c) Record the time immediately after the appearance of blue colour. (d) Record the time immediately before the appearance of blue colour. (e) Always keep the concentration of sodium thiosulphate solution more than that of KI solution. Choose the correct answer from the options given below. (A) (a), (b), (c) only (B) (a), (d), (e) only (C) (d), (e) only (D) (a), (b), (e) only

1. (a), (b), (c) only
2. (a), (d), (e) only
3. (d), (e) only
4. (a), (b), (e) only

Correct answer: (a), (b), (c) only

Solution

Option (a) is correct because freshly prepared starch solution ensures accurate detection of iodine, while (b) is important to maintain the reaction conditions, and (c) is necessary to measure the reaction time accurately as it reflects the moment the reaction reaches a visible endpoint.

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