NIOS Class 12 Chemistry Chapter 15 Adsorption and Catalysis Solutions English Medium As Per New Syllabus to each chapter is provided in the list so that you can easily browse throughout different chapters NIOS Class 12 Chemistry Chapter 15 Adsorption and Catalysis Notes in English and select need one. NIOS Class 12 Chemistry Solutions English Medium Download PDF. NIOS Study Material of Class 12 Chemistry Notes Paper Code: 313.
NIOS Class 12 Chemistry Chapter 15 Adsorption and Catalysis
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Adsorption and Catalysis
Chapter: 15
| Module – VI: Chemistry of Elements |
INTEXT QUESTIONS 15.1
1. Indicate which of the following statements are true or false. (T/F)
(i) More easily liquifiable gases are absorbed more strongly.
Ans: True.
(ii) Non-porous adsorbents would absorb more quantity of a gas than porous adsorbents under similar conditions.
Ans: Fals.
(iii) The extent of adsorption increases with rise in temperature.
Ans: False.
(iv) Chemisorption is highly specific in nature.
Ans: True.
(v) Adsorption can occur from solutions also.
Ans: True.
INTEXT QUESTIONS 15.2
1. List any two characteristics of a catalyst.
Ans: The following are the general characteristics of a catalyst :
(i) A catalyst remains unchanged at the end of the reaction.
(ii) A small quantity of the catalyst is generally enough.
2. A small amount of alcohol when added to a solution of sodium sulphite slows down its oxidation to sodium sulphate. What type of catalyst is alcohol?
Ans: Negative catalyst.
3. How would the activation energy be affected in the above reaction (given in Q.No.2) on adding the alcohol?
Ans: Increase.
4. Addition of molybdenum enhances the catalytic activity of iron in the Haber’s process for the manufacture of ammonia. What are the substances like molybdenum called?
Ans: Promoters.
TERMINAL EXERCISE
1. What is the difference between adsorption and absorption?
Ans: The difference between adsorption and absorption lies in how a substance is taken in:
| Aspect | Adsorption | Absorption |
| Definition | Accumulation of molecules on the surface of a material | Penetration of molecules into the bulk (interior) of a material |
| Nature | Surface phenomenon | Bulk phenomenon |
| Speed | Usually rapid at first, then slows down | Usually uniform and slower |
| Example | Charcoal adsorbing gases like ammonia or sulfur dioxide | Sponge absorbing water |
| Temperature effect | Generally decreases with rise in temperature | increase or remain constant |
| Equilibrium | Reaches equilibrium quickly | Takes longer to reach equilibrium |
2. Distinguish between physical and chemical adsorption.
Ans: Here is a clear comparison between physical adsorption and chemical adsorption:
| Aspect | Physical Adsorption (Physisorption) | Chemical Adsorption (Chemisorption) |
| Nature of force | Weak van der Waals forces | Strong chemical (covalent or ionic) bonds |
| Heat of adsorption | Low (20–40 kJ/mol) | High (80–200 kJ/mol) |
| Specificity | Not specific — occurs with many substances | Highly specific — depends on the chemical nature |
| Temperature dependence | Decreases with increase in temperature (exothermic) | Increases with temperature up to a point (activation energy needed) |
| Reversibility | Generally reversible | Usually irreversible |
| Layer formation | Can form multi-molecular layers | Forms only monolayer |
| Activation energy | No or very low activation energy needed | High activation energy required |
| Example | Adsorption of gases like O₂ or N₂ on charcoal | Adsorption of hydrogen on nickel surface |
3. List the factors that affect adsorption.
Ans: The following factors influence the extent and efficiency of adsorption:
(i) Nature of Adsorbent: Surface area, pore size, and chemical nature of the adsorbent.
(ii) Nature of Adsorbate: Chemical properties, molecular size, and polarity of the adsorbate.
(iii) Temperature: Generally, adsorption decreases with increasing temperature.
(iv) Pressure: Increasing pressure increases adsorption, especially for gases.
(v) Surface Area: Larger surface area of the adsorbent enhances adsorption.
(vi) Activation of Adsorbent: Pre-treatment or activation of the adsorbent can increase its adsorption capacity.
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