Simplifications of General Energy Balance

Question 1
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In an open system, what is the enthalpy change is heat taken from it is 10 J?
0
-10 J
10 J
Cannot be determined
Explanation:
For an open system, ∆H = Q, => ∆H = -10 J.
Question 2
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Which of the following is true for isothermal ideal gases?
∆T = 0
∆U = 0
∆H = 0
All of the mentioned
Explanation:
For isothermal ideal gases, ∆T = 0, => ∆U = 0, => ∆H = 0.
Question 3
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In an open, steady state system if the heat transferred is 10 J and work done by the system is 5 J, what is the change in Potential energy (neglect kinetic energy)?
5 J
-5J
15 J
-15 J
Explanation:
W + Q = ∆PE, => ∆PE = 10 – 5 = 5 J.
Question 4
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What is the work done for an isochoric process?
Positive
Negative
Zero
Cannot say
Explanation:
W = -PdV, for isochoric process dV = 0, => W = 0.
Question 5
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In an open, steady state adiabatic process if the change in kinetic energy is 10 J and change in potential energy is 15 J, what is the work done by the system?
10 J
15 J
25 J
-25 J
Explanation:
-W = ∆KE + ∆PE = 10 + 15 = 25, => W = -25 J.
Question 6
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What is the work done for an ideal gas isothermal process?
Zero
Equal to heat transferred
Equal to change in internal energy
Cannot say
Explanation:
For ideal gas isothermal process ∆U = 0, => Work done is equal to heat transferred.
Question 7
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What is the work done by an open steady-state system if heat transferred to it is 10 J?
0
-10 J
10 J
Cannot be determined
Explanation:
In steady state system ∆E = 0, => Work done by the system = 10 J.
Question 8
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In a closed system, change in internal energy is 10 J and heat transferred to it is 10 J what is the work done by the system?
0
10 J
-20 J
20 J
Explanation:
∆E = W + Q, => W = 10 – 10 = 0.
Question 9
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What is the work done for an isobaric process?
P∆V
V∆P
PV
None of the mentioned
Explanation:
For isobaric process ∆P = 0, => W = P∆V.
Question 10
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If the system is insulated which of the following might the process be?
Isothermal
Isobaric
Isochoric
Adiabatic
Explanation:
Since the system is insulated, => Q = 0, => Process is adiabatic.