This set of Waste Water Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Adsorption and Water Treatment”.
1. Adsorption is an endothermic process.
Explanation: The phenomenon of adsorption is essentially an attraction of absorbable molecules to an adsorbent surface. Adsorption is nearly always an exothermic process.
2. Chemical adsorption takes place at high temperature.
Explanation: Chemical adsorption takes place at high temperature whereas physical adsorption takes place at low temperature and is reversible.
3. Which force holds the molecules in physical adsorption?
a) Friction force
b) Van der waals force
c) Tension force
d) Nuclear force
Explanation: It is the common type of adsorption. The basic feature of physical adsorption is that the adsorbate molecules are held at the surface of the adsorbent by weak van der Waals forces. These are the forces that exist between particles of all matter.
4. What is the lowest enthalpy of adsorption for physical adsorption?
a) 5 KJ mol-1
b) 10 KJ mol-1
c) 15 KJ mol-1
d) 25 KJ mol-1
Explanation: The physical adsorption is observed on the surface of any solid only. The extent of adsorption varies according to the nature of the adsorbent and adsorbate. Physical adsorption is characterized by low enthalpy of adsorption that is about 10-40 KJ/ mol.
5. What is the highest enthalpy of adsorption for chemical adsorption?
a) 100 KJ mol-1
b) 200 KJ mol-1
c) 300 KJ mol-1
d) 400 KJ mol-1
Explanation: The enthalpy of chemisorption is as high as that of chemical bonds (bond enthalpies) and is in the range of 40 – 400 kJ mol-1. Like most of the chemical changes, it is irreversible.
6. Physical adsorption is also called as _________
Explanation: Physical adsorption is also called as Physisorption. Since physical adsorption is an exothermic process, it occurs more readily at lower temperatures and decreases with increase in temperature.
7. Chemical adsorption is also called as _____
d) Chemical sorption
Explanation: Chemical adsorption is also called as chemisorption. The range of enthalpy for chemisorption is as high as that of chemical bonds and is of 40 – 400 kJ mol-1.
8. Physical adsorption ________ with increase in temperature.
c) Remains same
Explanation: Since physical adsorption is an exothermic process, it occurs more readily at lower temperatures and decreases with increase in temperature.
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