Question

What are the units of k in the following rate law?

Answer 1

Answer:

B. $\frac{1}{M^{2} s }$

Explanation:

The unit for rate is M/s while the unit for each molecule should be M. You can find the unit for k by putting the units for rate and the molecules into the equation

rate= k{X][Y]

M/s= k * $M^{2}$ * $M^{1}$

k= (M/s) / ($M^{3}$)

k= $\frac{1}{M^{2} s }$

You can also use this predetermined formula to solve this problem faster: k= $\frac{M^{1-n} }{s }$

Where n is the number of molecule. There are 3 molecule(2X and 1Y) so n=3, so

k= $\frac{M^{1-n} }{s }$

k= $\frac{M^{1-3} }{s }$= $\frac{m^{-2}}{s}$= $\frac{1}{M^{2} s }$