Nitrogen gas reacts with hydrogen gas to produce ammonia gas .
Write a balanced chemical equation for this reaction.

N2 (g) + 3 H2 (g) -> 2 NH3 (g)

Explanation:

First, write the reactants on the left and the products on the right side. Also, add the states of matter after the reactants and products. Note, nitrogen gas is written as N2 and hydrogen gas is written as H2, not N or H.

N2 (g) + H2 (g) -> NH3 (g)

Next, balance the equation! Since there are two nitrogens on the left, add a two to the product NH3. Now there are 6 hydrogens on the right side. To balance that, add a 3 to the H2.

N2 (g) + 3 H2 (g) -> 2 NH3 (g)

Double checking, there are 2 nitrogens and 6 hydrogens on each side.

Success!

a corroding iron, if that's one of your choices

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)