Question

What is graham's law of diffusion?​

Answer 1

Answer:

The law is as follows –

The rate of diffusion of gases is inversely proportional to the square root of their densities.

As a result, if the molecular weight of one gas is 4 times that of the other, it diffuses or escapes through tiny pinholes in a vessel at half the rate compared to the other. This law renders a base to separate isotopes by diffusion.

Answer 2

★ Concept

The molecular masses of gases, volatile & non-volatile substance is determined by several methods. These methods may include Molar Volume Method, Regnault's Method, Diffusion Method & even with the help of Ideal gas equation, Relative molecular masses of gases are, thus, determined. Here, the Graham's law of diffusion comes under the concept of Diffusion Method. Let's understand the Graham's law of Diffusion !!

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$\underline{\bf{ \purple{Diffusion \: Method }}}$

The spontaneous intermixing of two or more gases even against gravity is called Diffusion. The diffusion of gases obeys an important law known as Graham's Law of diffusion. The Law can be stated as follows.

"At constant temperature and pressure, the ratio of diffusion of a gas is inversely proportional to the square root of its density".

$\sf i.e \quad \underline{ \boxed{ \bf \: r \propto \: \dfrac{1}{ \sqrt{d} }}} \\ \sf(at \: constant \: temp. and \: pressure)$

If r₁ and r₂ are the rates of Diffusion of two gases at the same temperature and pressure while d₁ and d₂ are their densities respectively, then according to this law,

$\therefore \quad \sf \dfrac{r_1}{r_2} = \dfrac{ \sqrt{d_2} }{ \sqrt{d_1} } \\ \sf\quad \: (at \: constant \: temp. \: and \: pressure)$

Since molecular mass of a gas is twice its vapour density i.e, M = 2 × V.D., we have

$\quad \sf \dfrac{r_1}{r_2} = \sqrt\dfrac{{d_2}}{{d_1}} = \sqrt{ \dfrac{M_2}{M_1} }$

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Additional Information

✰ Relative Molecular Masses of Gases

Several methods are available for the analysis of molecular masses of Gases. Some of the important ones are as follows :-

• Molar volume Method.
• Regnault's Method.
• Diffusion Method.
• With the help of Ideal Gas Equation.

✰ Molecular Masses of Volatile Substances

Molecular masses of a volatile substance can be determined by several methods like - Victor Meyer's Method.