Question

For $C{{H}_{3}}Br+O{{H}^{-}}\to C{{H}_{3}}OH+B{{r}^{-}}$, the rate of reaction is given by the expression is:

Answer 1

Hint: When a nucleophile attacks an electrophile to replace a leaving group then it is called substitution reaction. This reaction proceeds via $S{{N}_{2}}$ mechanism. The rate of a reaction is the speed at which a chemical reaction takes place.

Complete answer:
The rate of a reaction is proportional to the increase in the concentration of a product per unit time and to the decrease in the concentration of the reactant per unit time.
The rate of a reaction is affected by reactant concentration, physical state of reactants, pressure, surface area, temperature and presence of catalyst.
Nucleophilic reactions are those in which an electron rich nucleophile attacks a positively charged electrophile to replace a leaving group. Nucleophilic reactions are two types: $S{{N}_{1}}$ and $S{{N}_{2}}$ reactions.
$S{{N}_{1}}$ reactions are those in which an attack of nucleophile and departure of a leaving group takes place in two different steps.
The reaction $C{{H}_{3}}Br+O{{H}^{-}}\to C{{H}_{3}}OH+B{{r}^{-}}$ proceeds through $S{{N}_{2}}$ mechanism.
$S{{N}_{2}}$ reactions are those in which the addition of nucleophile and departure of the leaving group takes place in a single step. The carbon-nucleophile bond forms and carbon-leaving group bond breaks simultaneously through a transition state.
The rate of $S{{N}_{2}}$ reaction is given as: $R=k[S][N]$ where R is rate of reaction, k is rate constant, S is substrate and N is nucleophile.
The $S{{N}_{2}}$ reactions are second order reactions and rate of reaction depends on both the nucleophile and the substrate.
The rate of reaction is given by: $R=k[C{{H}_{3}}Br][O{{H}^{-}}]$

Note:
In $S{{N}_{2}}$ reaction inversion of configuration takes place and in $S{{N}_{1}}$ reaction the product formed is racemic mixture. Racemic mixture contains equal quantities of two enantiomers.