Answer:
16.0 moles
Step-by-step explanation:
The reaction is:

It is given that
is present in large excess. It means that
is the limiting reagent and the formation of the product is governed by
.
From the reaction stoichiometry,
3 moles of
on reaction forms 2 moles of

Also,
1 mole of
on reaction forms 2/3 moles of

Given moles = 24.0 moles
24 moles of
on reaction forms (2/3)×24.0 moles of

Moles of
= 16.0 moles