What is the molecular formula of a compound whose molar mass is 88.0 and whose percent composition is 54.5% carbon, 9.1% hydrogen, and 36.4% oxygen?

C4H8O2

Explanation:

The molar mass of the compound we're looking for is 88.

54.5% of 88 is 4, this is how many carbons will be in the compound.

9.1% of 88 is 8, this is your hydrogens.

and 36.4% of 88 is roughly 3, however if you subtract the previous amounts to round down, you get 2; the oxygen amount.

Combine them all and you get C4H8O2

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