Question

Predict the overall reaction from the following two-step mechanism: A2+2AB→→A2A2B(slow)(fast)

Answer 1

The two-step mechanism is:

$2A-\ \textgreater \ A_2$    slow

$A_2+B -\ \textgreater \ A_2B$    fast


The overall reaction is the sum of the two reactions:

$2A+A_2+B -\ \textgreater \ A_2+A_2B$

Now you can cancel the the terms that appear in both sideds:

$2A+B -\ \textgreater \ A_2B$

The fact that one reaction and the other is fast does not change the product. It does change the spped (rate) of reaction, but that is a different point.