JEE Main 2022 · 28 Jul · Shift 1 · Chemistry Q80

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ChemistrySingle correct+4 / -1Question 80 of 90

For kinetic study of the reaction of iodide ion with $\mathrm{H_2O_2}$ 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), (B), (C) only

(A), (D), (E) only

(D), (E) only

(A), (B), (E) only

Answer and worked solution

Official answer: A

Iodine clock.

Use freshly prepared starch (A).
Keep thiosulphate below KI, so it runs out and the blue appears (B).
Record the time at the first appearance of blue (C).

(A)

Topics:Rate of reaction and rate law Detection of functional groups

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JEE Main 2022 · 28 Jul · Shift 1, Chemistry question 80