Question

A gaseous hydrogen and carbon containing compound is decomposed and found to contain 82.66% carbon and 17.34% hydrogen by mass. The mass of 158 mL of the gas, measured at 556 mmHg and 25 ∘C, was found to be 0.275 g. What is the molecular formula of the compound?

Answer 1

For the answer to the question above, I'll show the solution to my answers

moles C = 82.66 g/ 12.0111 g/mol=6.882 
moles H = 17.34 g/ 1.008 g/mol=17.20 

17.20/ 6.882 =2.5 => H 
6.882 / 6.882 = 1 => C 

to get whole numbers multiply by 2 
C2H5 ( empirical formula Molar mass = 29.062 g/mol) 

n = pV/RT = 0.732 x 0.158 L/ 0.08206 x 298 K= 0.00473 
molar mass = 0.275/ 0.00473 =58.1 g/mol 

58.1 / 29.062 = 2 

multiply by two the empirical formula 

C4H10