What is the concentration of A after 38.7 minutes for the reaction A → Products when the initial concentration of A is 0.800 M? (k = 0.00651 M/min

Question

What is the concentration of A after 38.7 minutes for the reaction A → Products when the initial concentration of A is 0.800 M? (k = 0.00651 M/min

Answer 1

Because we have units of M/min for the rate constant, this tells us this MUST BE A ZERO ORDER reaction.

The integrated rate law for a zero order reaction is [A] = [A]_o - kt

Substituting the known values and solving or [A], we have ....

[A] = [0.800 M] - (0.00651 M/min)(38.7 min)

[A] = 0.548 M

Answer 2

This question is impossible to answer without more information. In particular, you need to know the "order" of the reaction.

If the reaction is zeroth order, you use the 0th order integrated rate law:

[At] = [A0] - kt

So:

At (final concentration) = 0.8 - 0.00651*38.7

If first order, you use the 1th order integrated rate law:

ln(​[At]/​​[A0]​​​​​)=kt

2nd Order, use the following:

1/[At] = kt+1/[A0]

I would guess, based on the reaction, it is a first order reaction (decomposition with one substance usually is) but it is impossible to know for sure.