Question

Assuming no other changes, what is the effect of doubling only the concentration of the alkyl halide in the above SN2 reaction?

A) no change
B) triples the rate
C) rate is halved
D) doubles the rate
E) quadruples the rate

Answer 1

D) doubles the rate

Step-by-step explanation:

The given reaction is :

`$CH_3Br + OH^- \rightarrow CH_3OH+Br^-$`

For the
`SN^2` reaction, the rate of reaction depends upon the concentration of both the
`$\text{alkyl halide}$` as well as the
`\text{nucleophile.}`

That is the rate =
`$k[CH_3Br][OH^-]$`

Now if the
`$[CH_3Br]$` becomes
`$2[CH_3Br]$`, then the rate becomes double.

So the rate' is :

=
`$2k[CH_3Br][OH^-]$`

= 2 x rate

Therefore, the answer is (D) doubles the rate.