Answer
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Work Step by Step
Nitrogen molecules reacts with Hydrogen molecules to form ammonia (NH$_{3}$). The reaction can be written as-
N$_{2}$ + 3H$_{2}$ $\rightarrow$ 2NH$_{3}$
So one molecule of nitrogen reacts with three molecules of hydrogen to form two molecules of ammonia. Now according to Avogadro's hypothesis we can say that 1 volume of nitrogen reacts with 3 volumes of hydrogen to make 2 volumes of gaseous product.
