an unknown compound contains 85.64% carbon with the remainder hydrogen. It has a molar mass of 42.08 g/mol. Find its empirical and molecular formulas.

Question

an unknown compound contains 85.64% carbon  with the remainder hydrogen. It has a molar mass of 42.08 g/mol. Find its empirical and molecular formulas.

bobpursley · Answer

I think I did this yesterday.
Assume 100 grams comound
MolesC=85.64/12= 7.14
MolesH=14.36/1=14.36
now divide both moles by the smaller of the two (7.14) so in the end, the ratio is CH2.
But the molmass is 42, so take the mole mass of CH2 (14), divide it into 42, giving 3. The molecular formula is C3H6