Question

An organic compound has the following composition: 52.2% carbon, 34.8% oxygen, and 13.0% hydrogen. If its molar mass is 92%, what is the molecular formula?

a) CH₄O
b) C₃H₇O
c) C₂H₆O
d) C₄H₁₀O₂

Answer 1

The empirical formula of a compound is found by converting the percent composition to grams, then to moles, and finding the simplest whole number ratio of elements. Without the correct molar mass value, the exact molecular formula cannot be determined; 92% is not a valid expression for molar mass.

Step-by-step explanation:

To determine the empirical formula of an organic compound based on its percent composition and molar mass, we use the following steps:

1. Convert the percentages to grams. Assume a 100 g sample, so we have 52.2 g of carbon (C), 34.8 g of oxygen (O), and 13.0 g of hydrogen (H).
2. Convert the mass of each element to moles by dividing by the atomic mass of each element (C: 12.01 g/mol, H: 1.008 g/mol, O: 16.00 g/mol).
3. Find the simplest whole number ratio of moles of each element.
4. Use the molar mass to convert the empirical formula to the molecular formula.

The molar mass is given as "92%", which is not a standard expression for molar mass. Assuming the molar mass is actually 92 g/mol, we would calculate the empirical formula and then determine how many empirical units are in the molecule to get the molecular formula that has the mass closest to 92 g/mol.