For the reaction

CHEMISTRY · Subjective · A Level · Chemistry · Rate equations · Rate equations

Problem

For the reaction

\mathrm{S_2O_8^{2-}(aq)+2\,I^-(aq)\rightarrow 2\,SO_4^{2-}(aq)+I_2(aq)}

, the rate law is first order in

\mathrm{S_2O_8^{2-}}

and first order in

\mathrm{I^-}

. In Trial 1,

[\mathrm{S_2O_8^{2-}}]=0.10\,\text{M}

and

[\mathrm{I^-}]=0.10\,\text{M}

, giving an initial rate of

2.0\times10^{-5}\,\text{M\,s}^{-1}

. In Trial 2, only

[\mathrm{S_2O_8^{2-}}]

is doubled to

0.20\,\text{M}

. Determine the initial rate in Trial 2 and briefly explain how the change in concentration affects collision frequency.