Question

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

Answer 1

The percentage of sodium in this compound is the molar mass of sodium divided by the molar mass of sodium azide.

The molar mass (atomic weight ) of sodium is 23.0 grams/mole and the molar mass of sodium azide, `NaN_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.

The percentage of sodium is 23.0 /65.0 x 100 % = 35 %.