the rate of effusion of h2 as compared to an unknown gas is 4.673 times faster. calculate the molar mass of the unknown gas. the rate of effusion of h2 as compared to an unknown gas is 9 times faster. calculate the molar mass of the unknown gas. he diffuses 4 times faster than an unknown gas. what is the molar mass of the unknown gas? a carbon dioxide molecule travels at 45.0 m/s at a certain temperature. at the same temperature, find the velocity of an oxygen molecule. what is the molar mass of a gas that diffuses 2.16 times faster than xenon? what diatomic element is it?