The table below summarizes the experimental observations for the reaction shown. Use the data to answer the questions below.

Question

Answer 1

(a). To determine the order of each reactant, we want to compare experiments where the concentration of the reactant of interest changes while the other two remain constant.

For X: compare expt. 2 to 4. [X] doubles while [Y] and [Z] are constant. The rate increases 4 fold from 9x10^-4 to 3.6x10^-3. So, the reaction is SECOND ORDER IN X (2² =4)

For Y: compare expt. 2 to 3. [Y] doubles while [X] and [Z] are constant. The rate increases 8 fold from 9x10^-4 to 7.2x10^-3. So, the reaction is THIRD ORDER in Y. (2³ = 8)

For Z: compare expt. 1 to 2. [Z] triples while [X] and [Y] are constant. The rate increases 3 fold from 3x10^-4 to 9x10^-4. So, the reaction is FIRST ORDER IN Z. (3¹ = 3).

SUMMARY: Rate = k[X]²[Y]³[Z]

(b). To find the rate constant, we simply choose any 1 experiment and plug in the value of the rate and the concentrations and solve for k. I will choose expt. 1 for these calculations:

Rate = k[X]²[Y]³[Z]

3x10^-4 M/s) = k(0.04 M)²(0.10 M)³(0.06 M) = 1x10^-7 M⁶

k = 3x10^-4 M/s / 1x10^-7 M⁶

k = 3x10³ M^-5s^-1

(c). The complete rate law equation would be

rate = 3x10³ M^-5s^-1 [X]²[Y]³[Z]