An unknown compound analyzes to be 42.85% C, 7.20% H, and 49.95% N. A 0.915 g sample of the gas occupies 250. mL at 760. mm Hg and 100.°C. Type your answers using the format CH4 for CH4. Enter the elements in the order given.

Question

An unknown compound analyzes to be 42.85% C, 7.20% H, and 49.95% N. A 0.915 g sample of the gas occupies 250. mL at 760. mm Hg and 100.°C. Type your answers using the format CH4 for CH4. Enter the elements in the order given.
I have calculated the emperical formula to be CH2N, but I'm not sure how to calculate the molecular formula.

DrBob222 · Answer

I didn't check the empirical formula. We will assume that is correct. The empirical formula weight is 12+2+14 = 28.

Use PV = nRT to calculate n = number of moles. Remember P is in atm and T in Kelvin. Then since moles = grams/molar mass, you have moles and grams, calculate molar mass.
Then molar mass/empirical mass = some number. Round to whole number, which I will call x. The molecular formula, then, is (CH2N)_x