How can I find the percent compositions of N2S2?

To find the of N₂S₂, you divide the total mass of each atom by the molecular mass and multiply by 100 %.

% by mass = ##"mass of component"/"total mass"## × 100 %

Mass of 2 N atoms = 2 N atoms × ##(14.01"u")/(1"N atom")## = 28.02 u.

Mass of 2 S atoms = 2 S atoms × ##(32.06"u")/(1"S atom")## = 64.12 u

Mass of 1 N₂S₂ molecule = (28.02 + 64.12) u = 92.14 u

% of N = ##"mass of N"/"total mass"## × 100 % = ##(28.02"u")/(92.14"u")## × 100 % =30.41 %

% of S = ##"mass of S"/"total mass"## × 100 % = ##(64.12"u")/(92.14"u")## × 100 % =69.59 %