# Chemical Process Calculation Questions and Answers – Energy Balances – Work – II

This set of Chemical Process Calculation Puzzles focuses on “Work – II”.

1. ___________ occurs when a system causes a _______ to turn against an external mechanical resistance.
a) Mechanical work, Mechanical
b) Electrical work, Electrical
c) Shaft work, Shaft
d) Flow work, Flow

Explanation: Shaft work occurs when a system causes a shaft to turn against an external mechanical resistance.

2. When a shaft in the system turns a pump to pump water out of the system, the shaft work is
a) Positive
b) Negative
c) Zero
d) None of the mentioned

Explanation: Work is done by the system.

3. _____________ is performed on a system when the fluid is pushed in to the system by the surrounding.
a) Mechanical work
b) Electrical work
c) Shaft work
d) Flow work

Explanation: Flow work is performed on a system when the fluid is pushed in to the system by the surrounding.

4. In constant volume thermodynamic process work done is
a) Maximum
b) Minimum
c) Zero
d) None of the mentioned

Explanation: W = P(V2-V1).

5. For any irreversible process, the net entropy change is
a) Positive
b) zero
c) negative
d) infinite

Explanation: For any irreversible process, the net entropy change is Positive.
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6. The intensive property of thermodynamics is
a) Density
b) Mass
c) Energy
d) Volume

Explanation: Density does not depend on the amount of material present.

7. In an irreversible process, there is
a) gain of heat
b) loss of heat
c) no loss of heat
d) None of these

Explanation: The process is irreversible so there is a loss of heat.

8-10. An ideal gas is enclosed at 200 K and 100 KPa in a cylinder by a frictionless vessel and the gas slowly forces the piston so that the volume of gas
expands from 0.1 to 0.2 m3.
8. What is the number of moles(10^-3) of the gas?
a) 2
b) 4
c) 6
d) 8

Explanation: n = PV/RT = (100)(0.1)/(200)(8.314) .

9. What is the work done for isobaric process (100 KPa)?
a) 10 KJ
b) 20 KJ
c) 30 KJ
d) 40 KJ

Explanation: W = -P(V2-V1).

10. What is the work done for isothermal process (200 K)?
a) -3.24 KJ
b) -6.24 KJ
c) -9.24 KJ
d) -12.24 KJ