ideal gas, urgent?

Question

A compound contains only nitrogen and hydrogen and is 87.4% nitrogen by mass. A gaseous sample of the compound has a density of 0.977 g/L at 680. torr and 84.1°C. What is the molecular formula of the compound? (Type your answer using the format C4H6 for C4H6.)
please explain

Answer 1

N2H4. The N/H mass ratio is .874/.126, so the volume ratio is (.874/14) / (.126/1), or 1/2. So we have NH2, N2H4 or any other such compound with the 1/2 ratio. The density at 760 torr and 0 C is 0.977*760/680*(273+84.1)/273 = 1.428 g/L. Then 22.4 L has a mass of 31.99 g, which fits N2H4 (MW=28+4).