CThe answer is 64%.
(1) Calculate the molar mass of N2O which is the sume of atomic masses of its elements:
Mr(N2O) = 2Ar(N) + Ar(O)
Ar(N) = 14 g
Ar(O) = 16 g
Mr(N2O) = 2 14 + 16 = 28 + 16 = 42 g
(2) Calculate mass percentage of nitrogen in N2O.
Total mass is 44 g: 44g is 100%
Mass of nitrogen is 28 g: 28g is x%
44 g : 100% = 28 g : x
x = 28 g 100% : 44 g
x = 63.64% ≈ 64%
