Question

A chemical reaction proceeds into the following steps Step I,\hspace15mm 2A \rightleftharpoons X fast Step II,\hspace10mm X + B \rightleftharpoons Y slow Step III,\hspace10mm Y + B \rightleftharpoons Product fast The law for the overall reaction is

• A. $rate = k [A]^2$
• B. $rate = k [B]^2$
• C. $rate = k [A][B]$
• D. $rate = k [A]^2 [B]$

Answer 1

Answer: (D)

$rate = k [A]^2 [B]$

Answer 2

$\frac{dx}{dt} = k ' [X][B]$
From step I \hspace10mm K_{eq} = \frac{[X]}{[A]^2}
\hspace25mm [X] = K_{eq} [A]^2
\hspace25mm \frac{dx}{dt} = k' . K_{eq} [A]^2[B]
\hspace25mm = k [A]^2[B]