JEE Main · 2007 · 29 Apr 2007 · Offline · Chemical Kinetics

Consider the reaction,

2 A + B \to

Products
When concentration of

B

alone was doubled, the half-life did not change. When the concentration of

A

alone was doubled, the rate increased by two times. The unit of rate constant for this reaction is

(A) $L mol^{- 1} s^{- 1}$ ✓ Correct
(B)no unit
(C) $mol L^{- 1} s^{- 1}$
(D) $s^{- 1}$

Answer: (A)

Solution

That doubling the concentration of B leaves the half-life unchanged shows the reaction is first order in B, and that doubling A doubles the rate shows it is first order in A. The overall order is therefore

1 + 1 = 2

. For a second-order reaction the rate constant carries units of

L mo l^{- 1} s^{- 1}

JEE Main · 2007 · 29 Apr 2007 · Offline · Single correct option

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