(1) How is Freundlich Adsorption Isotherm used to correlate the experimental facts regarding the adsorption of gas at low, high and intermediate pressure ?

Asked by sudhanshubhushanroy 6th March 2018, 5:50 AM

Answered by Expert

Answer:

Freundlich Adsorption Isotherm:

The variation on extent or adsorption (x/m) when pressure (P) was given mathematically byFreundlich.

The following observations can be easily made:(i) At low pressure, the graph is the almost straight line which indicates the x/m is directly proportional to the pressure.

This may be expressed as:

x over m proportional to space p space space space space space o r space space space space space space space space x over m space equals space k p

(ii) At high pressure, the graph becomes almost constant which mean that x/m becomes independent of pressure.

This may be expressed as:

x over m space equals space c o n s tan t space space space space o r space space space space space x over m space proportional to space space p to the power of o space space space left parenthesis because space p to the power of o space equals space 1 right parenthesis space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space o r x over m equals space p k to the power of o space equals space k comma space space a s space p to the power of o space equals space 1 space

(pressure raised to the power zero = 1)

(iii) This, in the intermediate range of pressure, x/m will depend upon the power of pressure which lies between 0 and 1 i.e., the fractional power of pressure.

This may be expressed as:

x over m space proportional to space p to the power of 1 over n end exponent space semicolon space space x over m space equals space k p to the power of 1 over n end exponent

Calculation of k and n of adsorption isotherm: The constant k and n can be determined as explained below: Taking logarithms on both sides of the equation