A gas of unknown molecular mass was allowed to effuse through a small opening under constant-pressure conditions. It required 100 s for 1.0 L of the gas to effuse. Under identical experimental conditions it required 34 s for 1.0 L of O2 gas to effuse. Calculate the molar mass of the unknown gas.

269.12gmol-1

Explanation:

The molecular mass of the unknown gas is obtained from Graham's law. First the respective rates of diffusion for oxygen and the unknown gas are obtained from information given in the question. The relative molecular mass of oxygen gas is calculated based on the relative atomic mass of oxygen known to be 16. These are now substituted into the equation as shown in the image attached.