Question

A reaction has the rate law, rate = k[A]3[B]. Which change will cause the great­est in­crease in the reaction rate?

Answer 1

Answer:

Increasing the concentration of A will cause the greatest change over the rate.

Explanation:

Hello,

In this case, considering the given rate law, which is third-order with respect to A, changing its concentration, the rate will be significantly modified. For instance, suppose a concentration of A and B of 1M and a symbolic rate constant (k),  this causes the rate to be:

$r=k[1M]^3[1M]=1k\frac{M^4}{s}$

Then, if we change the concentration of A to 2 M holding the concentration of B in 1 M, the new rate constant will be:

$r=k[2M]^3[1M]=8k\frac{M^4}{s}$

Nevertheless, if we hold the concentration of A in 1 M and the concentration of B is now 2 M (same change), the new rate constant is:

$r=k[1M]^3[2M]=2k\frac{M^4}{s}$

It means that increasing the concentration of A will cause the greatest change over the rate.

Best regards.