Interpration of the rate law: For a hydrothertical reaction `X+Y+Zrazrr` products
the rate law is determined to be
`"Rate" =k[X][Y]^(2)`
What happens to the reaction rate when we make each of the following concentration changes ?
(a) We dobule the concentration of X without changing the concentration of Y or Z.
(b) We double the concentration of Y without changing the concentration of X or Z.
(c ) We double the concentrations of Z without changing the concentration of X or Y.
(d) We double all three concentrations simultaneously.
Strategy: Interpret the law to predict the changes in reaction rate. Remember that changing concentrations does not change the value of k.

Explanation

(a) According to the rate law expression, reaction is directly proportional to the first power of [X]. If we do not change [Y] or [Z], then doubling [X] (i.e., increasing [X] by a factor of 2) cause the reaction rate to increase by a factor of `2^(1)=2`, so the reaction rate doubles.
(b) Rate is directly proportional to the second power of [Y]. If we do not change [X] or [Z], then doubling [Y] (i.e., increasing [Y] by a factor of 2) cause the reaction rate to increase by a factor of `2^(2)=4`, so the reaction rate quadruples.
(c ) The reaction rate is indepent of [Z] so changing [Z] causes no change in reaction rate.
(d) Doubling all concentrations would cause the changes decscribed in (a), (b), and (c ) simultaneouly. The rate would incerase by a factor of 2 due to the change in [X], by a factor of 4 due to the change in [Y], and be unaffected by the change in [Z]. The result is that the reaction rate increases by a factor of `2^(1)xx2^(2)=8`.