The rate equation for the reaction $2 \mathrm{~A}+\mathrm{B} \longrightarrow \mathrm{C}$ is found to be: rate $= \mathrm{k}[\mathrm{A}][\mathrm{B}]$. The correct statement in relation to this reaction is that the

(B) values of k is independent of the initial concentration of A and B

(A) unit of K must be $\mathrm{s}^{-1}$

(C) rate of formation of C is twice the rate of disappearance of A

JEE Main · 2004 · 24 Apr 2004 · Offline · Chemical Kinetics

The rate equation for the reaction

2 A + B ⟶ C

is found to be: rate

= k [A] [B]

. The correct statement in relation to this reaction is that the

(A)unit of K must be $s^{- 1}$
(B)values of k is independent of the initial concentration of A and B✓ Correct
(C)rate of formation of C is twice the rate of disappearance of A
(D) $t_{1/2}$ is a constant

Answer: (B)

Solution

The rate law here is

rate = k [A] [B]

. The rate constant

k

is a property of the reaction at a set temperature and does not shift with the starting amounts of A or B. The other claims fall apart: for this overall second-order rate law the units of

k

are

M^{- 1} s^{- 1}

, not

s^{- 1}

; the stoichiometry makes the rate of formation of C half, not twice, the rate of loss of A; and a constant half-life belongs to first-order reactions, not to this one. So the correct statement is that

k

is independent of the initial concentrations.

JEE Main · 2004 · 24 Apr 2004 · Offline · Single correct option

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JEE Main · 2004 · 24 Apr 2004 · Offline · Chemical Kinetics

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