How can comparing the rates of effusion of gases X and Y allow the molar mass of Y to be calculated? Write an equation stating the relationship between the ratio of the X and Y rates of effusion and their molar masses, MX and MY.

Explanation:

Gases are:

Gas 1  = X

Gas 2  = Y

To calculate the rates of effusion we apply the Graham's Law of Diffusion of Gases.

The law relates the rate of diffusion or effusion of a gas to the type of molecule in the gas.

It is expressed as "the rate of diffusion or effusion of a gas is inversely proportional to the square root of its molecular mass or density at constant temperature and pressure".

A gas with low molecular mass can diffuse or effuse more rapidly than one with high molecular mass under similar conditions.

By this, we can express a mathematical relationship to solve for the molecular masses of the gases.

r is the rate of diffusion

m is the molecular mass

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.