Menthol is composed of carbon, hydrogen and oxygen. A 1.005 g sample is combusted, producing 0.2829 g carbon dioxide and 0.1159 g of water. If the molar mass of menthol is 156 g/mol, what are the empirical and molecular formulas of menthol?
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1. Solve for the mass of carbon from the given the mass of carbon dioxide.
mass of CO2 = 5.86 mg = 0.00586 g
mass of C = 0.00586 g CO2 x (12 g C/44 g CO2)
mass of C = 1.598 x 10-3 g
Note: 1 mole CO2 contains 1 mole C, hence, the mass of C relative to the mass of CO2 is (12 g C/44 g CO2).
2. Solve for the mass of hydrogen from the given the mass of water.
mass of H2O = 1.37 mg = 0.00137 g
mass of H = 0.00137 g H2O x (2 g H/18 g H2O)
mass of H = 1.522 x 10-4 g
Note: 1 mole H2O contains 2 moles H, hence, the mass of H relative to the mass of H2O is (2 g H/18 g H2O).
3. Determine the empirical formula of the compound.
Mnemonics in finding the empirical formula:
*Mass to Mole*
*Divide by small*
*Multiply 'till whole*
Elements in the ...
The expert examines a combustion analysis of toluene. The molar mass of menthol is analyzed.