# How can I find the percent composition of (NH4)2S?

Aug 6, 2014

You calculate the mass of each atom in a formula unit, divide by the formula mass, and multiply by 100 %.

For calculation purposes, we can write the formula of (NH₄)₂S as N₂H₈S.

Mass of N = 2 atoms N × $\left(14.01 \text{u")/(1"atom N}\right)$ = 28.02 u

Mass of H = 8 atoms H × $\left(1.008 \text{u")/(1"atom H}\right)$ = 8.064 u

Mass of S = 1 atom S × $\left(32.06 \text{u")/(1"atom S}\right)$ = 32.06 u

Mass of (NH₄)₂S = (28.01 + 8.064 + 32.06) u = 68.144 u

% S =$\left(28.02 \text{u")/(68.144"u}\right)$ × 100 % = 41.12 %

% H =$\left(8.064 \text{u")/(68.144"u}\right)$ × 100 % = 11.83 %

% N =$\left(32.06 \text{u")/(68.144"u}\right)$ × 100 % = 47.05 %