If the reaction 3 A + B + C $\to$ 2 D + E is first order overall,which of these could be the units of its rate constant,k?

Question

If the reaction 3 A + B +  C $\to$ 2 D + E is first order overall,which of these could be the units of its rate constant,k?

Quizplus · Accepted Answer

Since the reaction is first order overall, the rate expression can be written as:

rate = k[A]^3[B][C]^11

The units of k can be found by substituting the units of concentration for each reactant into the rate expression and simplifying:

rate = k[M]^3[M][M]^11 
rate = k[M]^15

Thus, the units of k are 1/time, or 1/s. Choice A is the only option that has the correct units.

If the Reaction 3 a + B + C →\to→