For $A + B P$ with $B$ in large excess, the half-life of $A$ does not depend on $[A]_{0}$ . It is $10 min$ when $[B]_{0} = 0.10 mol L^{- 1}$ and $2.5 min$ when $[B]_{0} = 0.20 mol L^{- 1}$ . Use $ln 2 = 0.693$ . The overall order and the rate constant of rate $= k [A]^{m} [B]^{n}$ are

Answer: A

A half-life independent of

[A]_{0}

gives

m = 1

. The pseudo first order constant is

k^{'} = 0.693/ t_{1/2}

: 0.0693 and 0.2772

mi n^{- 1}

for the two runs. The ratio is 4.0, so

2^{n} = 4

and

n = 2

. Overall order

= 1 + 2 = 3

and

k = k^{'} / [B]_{0}^{2} = 0.0693/0.0100 = 6.93 L^{2} mo l^{- 2} mi n^{- 1}