Chemical Engineering question bank on “Energy Balances for Closed, Steady-State Systems”.
1. What is ∆E for a steady-state system?
a) Positive
b) Negative
c) Zero
d) Cannot say
Answer: c
Clarification: Change in internal energy for a steady-state system is always zero.
2. 5 J of heat is supplied to a steady state system, what is the work done by the system?
a) – 5 J
b) 5 J
c) 0
d) 10 J
Answer: b
Clarification: 0 = 5 – W, => W = 5 J.
3. 10 J of heat is taken off from a steady state system, what is the work done on the system?
a) – 10 J
b) 10 J
c) – 5 J
d) 5 J
Answer: b
Clarification: 0 = – 10 + W, => W = 10 J.
4. 10 J of work is done on a steady state system, what is the heat supplied to the system?
a) – 10 J
b) 10 J
c) 5 J
d) 0
Answer: a
Clarification: 0 = 10 + Q, => Q = – 10 J.
5. 15 J of work is done by a steady state system, what is the heat supplied to the system?
a) – 15 J
b) 15 J
c) 10 J
d) – 10 J
Answer: b
Clarification: 0 = – 15 + Q, => Q = 15 J.
6. 10 J of heat and 5 J of work is supplied to a system and 20 J of heat is taken out, then the system is which of the following?
a) Steady state
b) Unsteady state
c) Closed
d) None of the mentioned
Answer: b
Clarification: ∆E = 10 + 5 – 20 = – 5 J which is not equal to zero, so the system is unsteady state system.
7. 15 J of heat and 10 J of work is supplied to a system and 25 J of heat is taken out, then the system is which of the following?
a) Steady state
b) Unsteady state
c) Closed
d) None of the mentioned
Answer: a
Clarification: ∆E = 15 + 10 – 25 = 0, so the system is steady state system.
8. 15 J of heat is supplied to a system and 15 J of work is done on the system, then the system is which of the following?
a) Steady state
b) Unsteady state
c) Closed
d) None of the mentioned
Answer: b
Clarification: ∆E = – 15 – 15 = – 30 J, which is not equal to zero, so the system is unsteady state system.
9. 1 J of heat is supplied to the system and 1 kJ of work is done by the system, then the system is which of the following?
a) Steady state
b) Unsteady state
c) Closed
d) None of the mentioned
Answer: b
Clarification: ∆E = 1 – 1000 = – 999 J, which is not equal to zero, so the system is unsteady state system.
10. 10 J of work and 5 J of heat is supplied to the system, then the system is which of the following?
a) Steady state
b) Unsteady state
c) Closed
d) None of the mentioned
Answer: b
Clarification: ∆E = 10 + 5 = 15 J, which is not equal to zero, so the system is unsteady state system.