Question

The number of statement/s which are the characteristics of physisorption is __________ 
A. It is highly specific in nature 
B. Enthalpy of adsorption is high 
C. It decreases with increase in temperature 
D. It results into unimolecular layer
E. No activation energy is needed

Hint:

Physisorption decreases with temperature and requires no activation energy, as it involves weak van der Waals forces.

Answer 1

Correct Answer: 2

The characteristics of physisorption include:

• It is non-specific in nature, as it occurs between different substances without specificity. Hence, Statement A ("It is highly specific in nature") is incorrect.
• The enthalpy of adsorption in physisorption is generally low, ranging from about 20 to 40 kJ/mol, due to weak van der Waals forces. Therefore, Statement B ("Enthalpy of adsorption is high") is incorrect.
• Physisorption decreases with an increase in temperature because it is an exothermic process. Hence, Statement C is correct.
• Physisorption commonly results in the formation of multimolecular layers at low temperatures. Therefore, Statement D ("It results into unimolecular layer") is incorrect.
• No significant activation energy is required for physisorption as it involves weak interactions. Thus, Statement E ("No activation energy is needed") is correct.

Based on the analysis, the characteristics of physisorption are highlighted in Statements C and E. Therefore, the number of correct characteristics from the options given is 2, which fits the expected range of 2,2.