Diffusion is the process by which particles move from an area of high concentration to an area of low concentration.


Graham’s law of diffusion states that the rate of diffusion of a gas is inversely proportional to the square root of its molecular weight. It means that lighter molecules diffuse faster than heavier molecules.


The ratio of the rate of diffusion of the given element to that of helium is 1.4. So, we can use Graham’s law of diffusion to calculate the molecular weight of the given element.

Let's assume the molecular weight of the given element is 'x'.

According to Graham’s law of diffusion,

(rate of diffusion of the given element) / (rate of diffusion of helium) = √(Molecular weight of Helium) / √(Molecular weight of given element)

1.4 = √4 / √x

Squaring both sides, we get:

1.4² = (2 / √x)²

1.96 = 4 / x

Hence, the molecular weight of the given element is:

x = 4 / 1.96

x = 2.04

Therefore, the molecular weight of the given element is 2.04.


The ratio of rate of diffusion of a given element to that of helium is 1.4. Using Graham’s law of diffusion, we can determine the molecular weight of the given element. The molecular weight of the given element is 2.04.

Rate of diffusion is inversely proportional to the molecular mass of the element