A 24.81 g gaseous sample contains 3.01 g C, 4.00 g O and 17.81 g Cl. What is the mass percentage of chlorine?

1. Divide the chlorine mass by the sample mass: 17.81 g / 24.81 g. 2. Multiplying by 100 percent gives 71.8 percent chlorine. 3. Carbon gives 3.01 g / 24.81 g = 12.1 percent, and oxygen gives 4.00 g / 24.81 g = 16.1 percent. 4. The three add to 100 percent, confirming that no element has been missed. 5. The value 82.4 percent would leave the other two elements with too little mass to reach 100 percent. _Source: OpenStax Chemistry (CC BY 4.0), Ch 3 "Composition of Substances and Solutions", section 3.2 Determining Empirical and Molecular Formulas_