Food Processing Unit Operations Multiple Choice Questions on “Absorption Principles”.
1. What is the alternative name for stripping?
a) Gas absorption
b) Gas desorption
c) Adsorption
d) Liquid desorption
Answer: b
Clarification: Gas desorption is also called as stripping. In gas desorption, the mass transfer is from the liquid phase to the gas phase. The principles for both gas absorption and gas desorption are the same.
2. What are types of absorption?
a) Physical absorption
b) Chemical absorption
c) Physical absorption and chemical absorption
d) Physical absorption, chemical absorption and microbial absorption
Answer: a
Clarification: Spray dyer is used to produce powder from the solution. It dries the solution stream and separates the solute and evaporates the solvent and forms vapor. The solid particles are collected in a cyclone or drum.
3. What is reactive absorption?
a) Chemical absorption
b) Physical absorption
c) Microbial absorption
d) Ion absorption
Answer: a
Clarification: When a strong base like aqueous sodium hydroxide is used as the absorbent to dissolve an acid gas, the absorption process is accompanied by a rapid and irreversible neutralization reaction in the liquid phase and the process is known as chemical absorption or reactive absorption.
4. Who invented the absorption refrigerator?
a) Albert Einstein
b) Ferdinand Carre
c) Robert Wilhelm Bunsen
d) Schuyler Skaats Wheeler
Answer: a
Clarification: Albert Einsteininvented the absorption refrigerator. Ferdinand Carreinvented an electric light regulator. Robert Wilhelm Bunsen invented the spectrometer. Schuyler Skaats Wheeler invented fans.
5. What is the principle of absorption spectroscopy?
a) Bound atoms in the ground state can absorb light of a certain wavelength
b) Free atoms in the ground state can absorb light of a certain wavelength
c) Bound atoms in the excited state can absorb light of a certain wavelength
d) Free atoms in the ground state can absorb radiation energy of a certain wavelength
Answer: b
Clarification: Absorption spectroscopy is based upon the principle that free atoms in the ground state can absorb light of a certain wavelength. Absorption is specificfor each element, and thus, no other elements can absorb this wavelength.
6. Which of the following factors that affect the selection of absorbent?
a) Viscosity should be low
b) Viscosity should be high
c) Low pressure drops
d) Low pressure drops and viscosity should be low
Answer: d
Clarification: Absorbent is defined as the material having ability to absorb another substance. Absorbents should usually be having low pressure drops in absorption tower and low viscosity for rapid absorption rates.
7. Which of the following is not an example for absorption?
a) Reaction of oxygen by fermentation broths
b) Removal of carbon dioxide from water-gas by absorption in water or in solutions of alkalis or amines
c) Reaction of hydrogen by petroleum fractions in processes to remove sulphur as hydrogen sulphide.
d) Liquid ammonium in air
Answer: d
Clarification: Examples of absorption are i. Absorption of nitrous gases in water or nitric acid, during nitric acid manufacture. ii. Removal of carbon monoxide from water-gas by absorption in solutions of copper complexes. iii. The production of hypochlorite by absorbing chlorine through alkaline solutions. iv. Absorption of hydrogen by petroleum fractions in processes to remove sulphur as hydrogen sulphide.
8. Which of the following statements about chemical absorption are correct?
Statement 1: Chemical reaction between the absorbed and the absorbing substances.
Statement 2: Depends upon the stoichiometry of the reaction.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: b
Clarification: When the absorption is reactive then it is called as chemical absorption. There will be a chemical reaction between the absorbed and the absorbing substances. It depends on the stoichiometry of the reaction and the concentration of its reactants.
9. What is law behind absorption?
a) Nernst’s distribution law
b) Henry’s law
c) Raoult’s law
d) Dalton’s law
Answer: a
Clarification: The Nernst’s distribution law also called as Distribution law. This law governs the distribution of solute between two non-miscible solvents. It is important to note that it should not undergo dissociation or association.
10. Which of the following statements about physical absorption are correct?
Statement 1: Example for physical absorption is the absorption of carbon dioxide into water.
Statement 2: Polar interactions between water and the molecules of the solid play an important role in physical absorption.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: b
Clarification: When the absorption is non-reactive then it is called as physical absorption. Polar interactions between water and molecules of solid play an important role in physical absorption. Example for physical absorption is the absorption of carbon dioxide into water. The hydrophilic solids readily absorb water.