Name: Graham's Diffusion Law
Uploaded: 2019-07-19
Duration: 9 min 43 s
Description: Gases diffuse at a different rate. Watch this video to understand Graham's diffusion law, which deals with the diffusion of gases. Have fun learning!

Question

What is numerical value (as obtained from consideration of dimension) of the molar gas constant ‘

R

’? How do you arrive at this value? How do you arrive at different units? (lit-atm, erg, cal, Joules) in which the molar gas constant is expressed?

Accepted Answer

$R$ is known as universal gas constant or molar gas constant and it has different values:

$R = 0.0821 L atm K^{- 1} {mol}^{- 1} R = 0.083 L bar K^{- 1} {mol}^{- 1} R = 8.314 J K^{- 1} {mol}^{- 1} R = 1.9872 cal K^{- 1} {mol}^{- 1} R = 8.314 \times 10^{7} erg K^{- 1} {mol}^{- 1}$

We know that the ideal equation, $PV = nRT$ $\dots \dots \dots \dots (i)$

And the SI values of $P, V, T$ and $n$ are,

$P = 1.01325 \times 10^{5} Pa = 1.01325 \frac{N}{m^{2}}$ , $V = 22.4 L = 22.4 \times 10^{- 3} m^{3}$

$T = 273 K$ and $n = 1 mole$

Putting all the values in the equation $(i)$ ,

$1.01325 \times 10^{5} \frac{N}{m^{2}} \times 22.4 \times 10^{- 3} m^{3} = 1 mol \times R \times 273 K R = \frac{1.01325 \times 10^{5} \times 22.4 \times 10^{- 3}}{1 \times 273} N - m {mol}^{- 1} K^{- 1} R = 8.314 joule {mol}^{- 1} K^{- 1} \dots \dots \dots \dots \dots (ii)$

The above value is the value of molar gas constant in SI unit.

Also, $1 cal = 4.18 joules$ , $1 joule = 10^{7} erg$ , $1 L - bar = 100 joules$ and $1 L - atm = 101.325 joules$

If we substitute all the units one by one in equation $(ii)$ , we will get the all different possible values of gas constant mentioned above.

What is numerical value (as obtained from consideration of dimension) of the molar gas constant ‘ $R$ ’? How do you arrive at this value? How do you arrive at different units? (lit-atm, erg, cal, Joules) in which the molar gas constant is expressed?

Important Questions on States of Matter : Gases and Liquids

Learn and Prepare for any exam you want !

What is numerical value (as obtained from consideration of dimension) of the molar gas constant ‘R’? How do you arrive at this value? How do you arrive at different units? (lit-atm, erg, cal, Joules) in which the molar gas constant is expressed?

Important Questions on States of Matter : Gases and Liquids

Learn and Prepare for any exam you want !

What is numerical value (as obtained from consideration of dimension) of the molar gas constant ‘ $R$ ’? How do you arrive at this value? How do you arrive at different units? (lit-atm, erg, cal, Joules) in which the molar gas constant is expressed?