The chemical equation for the formation of ammonia is unbalanced.

3H2(g) + N2(g) Right arrow. NH3(g)

If three molecules of hydrogen react with one molecule of nitrogen, how many molecules of ammonia would be formed?

1

2

3

4

The answer to your question is 2 molecules

Explanation:

Unbalanced chemical reaction

                   H₂(g)   +   N₂(g)   ⇒   NH₃ (g)

         Reactants         Elements          Products

                2                      H                       3

                2                      N                       1

Balanced chemical reaction

                   3H₂(g)   +   N₂(g)   ⇒   2NH₃ (g)

         Reactants         Elements          Products

                6                      H                       6

                2                      N                       2

From the balanced chemical reaction we conclude that when 3 molecules of hydrogen react with one molecule of nitrogen, 2 molecules of ammonia will be formed.