# How can I calculate the percentage by mass of sodium in sodium azide, NaN3(s); used in automobile air bags?

The molar mass (atomic weight ) of sodium is 23.0 grams/mole and the molar mass of sodium azide, $N a {N}_{3}$, is the mass of sodium, 23.0 gram/mole added to the molar mass of three atoms of nitrogen (14.0 x 3 = 42 gram/mole) which equals 65.0 grams/mole.