Food Processing Unit Operations Multiple Choice Questions on “Basic Drying Theory”.
1. Lyophilization is also known as ____________
a) freezedrying
b) sundrying
c) tunneldrying
d) mechanicaldrying
Answer: a
Clarification: Lyophilization is also called as freeze drying. It is a process where biological material is preserved by removing the water from sample. It is a twostep process, first the sample is freeze and then dry it under a vacuum at low temperatures.
2. What is a triple point of pure water?
a) -0.01°C
b) 0.01°C
c) 0.1°C
d) -0.1°C
Answer: b
Clarification: The triple point of pure water is at 0.01°C. The triple point is the condition in which the temperature and pressure of all three phases (gas, liquid and solid) can coexist in equilibrium.
3. Phase diagram is a graphical representation of the ________ states of a substance under different conditions of temperature and pressure.
a) physical
b) chemical
c) electromagnetic
d) mechanical
Answer: a
Clarification: Phase diagram is a graphical depiction of the physical conditions of a matter under different conditions of temperature and pressure. It has temperature on the x-axis and pressure on the y-axis.
4. __________ diagrams represent the phase behavior of mixtures containing three components.
a) Ternary phase
b) Tertiary phase
c) Tri phase
d) Term phase
Answer: a
Clarification: The ternary phase represents the behavior of three components in a mixture with a triangular diagram. These diagrams provide the data which is precise and accurate of the various components.
5. The effect of ______on the system is seen only as a phase change.
a) Latent heat
b) Specific heat
c) Enthalpy
d) Entropy
Answer: a
Clarification: Latent heat can be defined as the heat that is released or absorbed by a system during constant temperature process. The effect is seen only as a phase change like boiling of water or the melting of ice.
6. The term triple point was coined by ___________
a) Rudolf Clausius
b) Thomas Young
c) Joseph Black
d) James Thomson
Answer: d
Clarification: Rudolf Clausius invented the term entropy. Thomas Young invented the term enthalpy. Joseph Black invented the term latent heat. The term triple point was coined by James Thomson.
7. What is the critical point of water?
a) 374°C
b) 157.5°C
c) 31.0°C
d) 240.9°C
Answer: a
Clarification: The critical point of water is 374°C. The critical point of sulphuric acid is 157.5°C. The critical point of supercritical carbon dioxideis 31.0°C. The critical point of ethanol is 240.9°C.
8. What are factors depending on rate of drying?
a) Initial moisture content of the product
b) Composition of raw material
c) Temperature, relative humidity
d) Initial moisture content, composition, temperature, relative humidity of the product.
Answer: d
Clarification: Drying rate is defined as the mass of water removed per unit time per unit area. It depends on initial moisture content, composition, temperature, relative humidity of the product, Size, shape and arrangement of stacking of the raw material.
9. Who discovered critical point?
a) Joseph Black
b) Charles Cagniard de la Tour
c) Henri Becquerel
d) Stephen Gray
Answer: b
Clarification: Joseph Black discovered latent heat. Charles Cagniard de la Tour discovered critical piont. Henri Becquerel discovered radiation. Stephen Gray discovered electrical conduction.
10. Does boiling point increase with pressure?
a) True
b) False
Answer: a
Clarification: At higher altitudes, the atmospheric pressure is much lower therefore the boiling point is also lower. The boiling point depends on pressure up to the critical point. It is directly proportional to the pressure. At the critical point the gas and liquid properties are same.