Question

A stable compound consisting of 53.4% C, 11.0% H, and the remainder O has a molecular weight of 90 grams/mole. What is the molecular formula for the compound? A stable compound consisting of 53.4% C, 11.0% H, and the remainder O has a molecular weight of 90 grams/mole. What is the molecular formula for the compound? @Chemistry

Answer 1

%/ molecular weight = # of element in that compound.

53%/12 grams/mol of carbon = 4.4 Carbons
11%/1g/mol of H = 11 hydrogens
(100-(53+11))/16g/mol of O = 2.2 Oxygens

C4.4 H11 O2.2
So you have to add up to 90grams/mol ......So round down with the decimals
C4 H10 O2 = 90grams/mol

You could check your answer by taking one of the elements and seeing if it equals the right %. For example, there are 4 carbons and 4 carbons = 48g/mol. 48/90 = 53%