This set of tough Mass Transfer Questions & Answers focuses on “Moisture Concept of Drying”.
1. Find the moisture to be evaporated per kg of dried product if initial and final moisture content per kg of dry solid is 85% and 15%.
a) 0.5
b) 0.6
c) 0.7
d) 0.8
View Answer
Explanation: Moisture to dry = Initial moisture – final moisture content = 0.85 – 0.15 =0.7 per kg of dry solid.
2. Convert 80% of moisture in wet basis to dry basis ( kg water/kg dry solid)
a) 4
b) 8
c) 12
d) 16
View Answer
Explanation: 0.8/1-0.8 = 4 kg water/kg dry solid.
3. If the equilibrium vapour pressure is lower than pure liquid pressure then the moisture content is ___________
a) Bound moisture
b) Unbound moisture
c) Equilibrium moisture
d) None of the mentioned
View Answer
Explanation: Bound moisture is the inside moisture present inside the compound which can be removed only by unsaturated surface drying.
4. The substance moisture exerts equilibrium vapour pressure equals to vapour pressure of liquid is ________
a) Bound moisture
b) Unbound moisture
c) Equilibrium moisture
d) None of the mentioned
View Answer
Explanation: The saturated surface moisture is unbound moisture which equals the equilibrium vapour pressure.
5. The moisture which can be evaporated is bound moisture.
a) True
b) False
View Answer
Explanation: The moisture which can be evaporated is known as free moisture which is the moisture excess to equilibrium moisture.
6. The method of drying by conduction through materials are done by _________
a) Direct driers
b) Indirect driers
c) Tray driers
d) None of the mentioned
View Answer
Explanation: Conduction through metals is heating indirectly so here indirect driers are used.
7. The substance like food stuff, pharma products are dried by _______ drying.
a) Direct
b) Indirect
c) Freeze
d) None of the mentioned
View Answer
Explanation: The compounds have to be preserved carefully so for drying these products we need sublimation drying known as freeze drying.
8. The representation AB is known as
a) Bound moisture
b) Unbound moisture
c) Equilibrium moisture
d) None of the mentioned
View Answer
Explanation: The saturated region is the unbound moisture region.
9. The name of the curve between relative humidity and moisture content is equilibrium moisture curve.
a) True
b) False
View Answer
Explanation: The equilibrium moisture curve gives us the relation between relative saturation and moisture content.
10. Convert 5 kg of moisture /kg of dry solid to wet basis.
a) 3/6
b) 4/6
c) 5/6
d) 1
View Answer
Explanation: In wet basis, 5/(5+1) (kg of moisture/kg of wet solid) = 5/6.
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