For 3A -> B the rate of the reaction is defined as r = -(1)/(3)(d[A])/(dt) and the rate law is r = k[A]^2. At [A] = 0.2 M, A disappears at 2.40x10^-3 M s^-1. The value of k is

JEE Advanced levelSingle correct optionDifficulty 3 of 3ck024

For $3 A B$ the rate of the reaction is defined as $r = - \frac{1}{3} \frac{d [ A ]}{d t}$ and the rate law is $r = k [A]^{2}$ . At $[A] = 0.2 M$ , $A$ disappears at $2.40 \times 1 0^{- 3} M s^{- 1}$ . The value of $k$ is

The rate of reaction is the rate of disappearance of A divided by 3:

r = 2.40 \times 1 0^{- 3} /3 = 8.00 \times 1 0^{- 4} M s^{- 1}

. Then

k = r / [A]^{2} = 8.00 \times 1 0^{- 4} /0.04 = 0.02 L mo l^{- 1} s^{- 1}

. The value 0.06 results from forgetting the factor 1/3.