Riphah International University Islamabad Main Campus

• CHEMISTRY 143

• Empirical/Molecular Formula Practice Worksheet Directions: Find the empirical AND molecular formulas given the percent compositions or masses. SHOW YOUR WORK to receive full credit. 1. An unknown compound is found to contain 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen with a molecular mass of 60.0 g/mol. C: 40g/12.011=3.33 mol/3.3mol=1 H: 6.7g/1.008=6.6mol/3.33 mol=2 0:53.3g/15.999=3.33mol/3.33mol=1 Molar mass= 12.011 g per mol + 2 (1.008)g per mol + 15.999 per mol = 30.026g per mol Empirical Formula: ________________ Molecular Formula: _______________________ 2. A hydrocarbon is a compound comprised of carbon and hydrogen atoms. An unknown hydrocarbon is