Question

A gas consists of 85.7 % carbon and 14.3 % hydrogen, by weigh. A sample of this gas weighing 0.673 g occupies 729 mL at a pressure of 720.0 mmHg and a temperature of 77 degree C. Calculate its empirical and molecular formulas.

a. CH,C₂H₂
B. CH₂,C₂H₄
C. CH₂, C₃H₆
D. CH₃,C₂H₆
E. CH₄,CH₄

Answer 1

To determine the empirical formula, convert the percentage of each element into grams and relate the moles of carbon to the moles of hydrogen. The empirical formula is CH₂. To determine the molecular formula, use the provided values to compute the molar mass of the gas.

Step-by-step explanation:

To determine the empirical formula of the gas, we can assume 100 g and convert the percentage of each element into grams. By doing this, we can determine the number of moles of carbon and hydrogen in the 100-g sample of gas. Dividing by the smallest number of moles allows us to relate the number of moles of carbon to the number of moles of hydrogen. The empirical formula is CH₂ (empirical mass of 14.03 g/empirical unit).

To determine the molecular formula, we need to use the provided values for mass, pressure, temperature, and volume to compute the molar mass of the gas.