The number of incorrect statement/s from the following is/are ____
A. Water vapours are adsorbed by anhydrous calcium chloride.
B. There is a decrease in surface energy during adsorption.
C. As the adsorption proceeds, $\Delta H$ becomes more and more negative.
D. Adsorption is accompanied by decrease in entropy of the system.
A. Water vapours are adsorbed by anhydrous calcium chloride.
B. There is a decrease in surface energy during adsorption.
C. As the adsorption proceeds, $\Delta H$ becomes more and more negative.
D. Adsorption is accompanied by decrease in entropy of the system.
Correct Answer: 2
Solution and Explanation
A: Water vapours are adsorbed by calcium chloride. Calcium chloride (CaCl\(_2\)) is a hygroscopic substance, meaning it has the ability to adsorb water vapors from the air. The water molecules are attracted to the surface of the calcium chloride, where they adhere through adsorption.
C: As the adsorption proceeds, \(\Delta H\) becomes less and less negative. In the case of adsorption, the enthalpy change (\(\Delta H\)) is initially negative because the process releases energy due to the attractive forces between the adsorbate and the adsorbent. However, as more water is adsorbed, the adsorption sites become occupied, and the heat released decreases, making \(\Delta H\) less negative.
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Concepts Used:
Surface Chemistry
The study of the chemical phenomena that occur at the interface of two surfaces which can be solid-liquid, solid-gas, solid-vacuum, liquid-gas, etc.
Read Also: Surface Chemistry
Applications of surface chemistry are:
Adsorption:
The process of attraction and aggregation of the molecules of a substance on the surface of a solid is known as adsorption. For Example, N2 adsorbs on the surface of activated charcoal
Two types of adsorption are:-
- Chemisorption: It is also known as Chemical Adsorption.
- Physisorption: It is also known as Physical Adsorption.
Corrosion:
The process through which the refined metals convert themselves into more stable compounds is known as corrosion.
Crystallisation:
The type of technique used in order to purify the substances to separate Solids from liquids is known as crystallisation.
Heterogeneous Catalysis:
The process wherein a catalyst is used in order to increase the rate of a chemical reaction is known as catalysis. The catalyst does not undergo any transformation and can be recovered in a chemically unchanged state.
There are two types of catalysis:-
- When the catalyst involved and the reacting substances are same states of matter or in the same phase, it is known as Homogeneous Catalysis.
- When the catalyst involved and the reacting substances are in different states of matter or different phases, it is known as Heterogeneous Catalysis.