For kinetic study of the reaction of iodide ion with 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) 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✓ Correct
- (B)(A), (D), (E) only
- (C)(D), (E) only
- (D)(A), (B), (E) only
Answer: (A)
Solution
In the iodine clock reaction (kinetic study of iodide with ): (A) is correct - fresh starch solution gives a sharp color change. (B) is correct - sodium thiosulphate must be in limited amount (less than KI) so it gets consumed first, allowing iodine to accumulate and react with starch. (C) is correct - time is recorded immediately after blue color appears. (D) is incorrect - time is recorded after, not before. (E) is incorrect - thiosulphate concentration should be less, not more. Therefore, (A), (B), (C) are correct.
JEE Main · 2022 · 28 Jul 2022 · Shift 1 · Single correct option