SOLUTION:
The balanced chemical equation for the reaction between nitrogen gas (
) and hydrogen gas (
) is:

According to the stoichiometry of the reaction, 1 mole of
reacts with 3 moles of
to produce 2 moles of
.
Therefore, to determine how many moles of
are needed to react with 7.5 moles of
, we need to use the mole ratio between
and
:

We can use this ratio to set up a proportion:

Solving for x, we get:

2.5 moles of
are needed to react with 7.5 moles of
.
