The reaction A+B⟶C+D rate=𝑘[A][B]2 has an initial rate of 0.0720 M/s.

Question

What will the initial rate be if [A] is halved and [B] is tripled?

What will the initial rate be if [A] is tripled and [B] is halved?

Answer 1

I see that there is an additional part to the question that I neglected to answer in my first response. I hope that you understood the process for the first half of the answer. If so, you should be able to do the second part. I'll show you below.

Rate = k[A][B]²

This means that the rate changes directly as a function of [A] and squared as a function of [B].

So, if we use 1/2 the [A] and 3x the [B], we essentially can write the rate law as...

rate = k[0.5][3]²

rate = 4.5k which means that the rate will be 4.5 x the original given rate (since k is constant)

Initial rate under these conditions will be 4.5 x 0.0720 M/s = 0.324 M/s

If [A] is tripled and [B] is halved

Rate = k[A][B]²

rate = k[3][0.5]²

rate = 0.75k which means that the rate will be 0.75 (three quarters) the original rate (since k is constant)

Initial rate under these conditions will be 0.75 x 0.0720 M/s = 0.054 M/s