# Chemical Engineering Questions and Answers – Heat Capacity Equations

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This set of Basic Chemical Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Heat Capacity Equations”.

1. Water having CP = 10 J/oC, is heated from 10oC to 50oC, what is the enthalpy change?
a) 100 J
b) 250 J
c) 400 J
d) 500 J

Explanation: ∆H = 105010.dT = 10*40 = 400 J.

2. Liquid benzene having CP = 29 J/oC, is heated from 5oC to 10oC, what is the enthalpy change?
a) 29 J
b) 145 J
c) 195 J
d) 290 J

Explanation: ∆H = 51029.dT = 29*5 = 145 J.

3. Ice having CP = 15 J/oC, is heated from -10oC to -4oC, what is the enthalpy change?
a) 30 J
b) 60 J
c) 90 J
d) 120 J

Explanation: ∆H = -10-415.dT = 15*6 = 90 J.

4. Steam having CP = 105 J/oC, is heated from 100oC to 104oC, what is the enthalpy change?
a) 210 J
b) 420 J
c) 630 J
d) 840 J

Explanation: ∆H = 100104105.dT = 105*4 = 420 J.

5. Cyclohexane having CP = 48 J/oC, is heated from 50oC to 55oC, what is the enthalpy change?
a) 240 J
b) 480 J
c) 720 J
d) 960 J

Explanation: ∆H = 505548.dT = 48*5 = 240 J.

6. What is the value of CP – CV for ideal gases?
a) 0
b) R/2
c) R
d) 2R

Explanation: For ideal gases CP = CV + R.

7. A mixture contains 20% O2 with CP = 15 J/oC and 80% CO2 with CP = 20 J/oC, what is the average CP of mixture?
a) 3 J/oC
b) 9 J/oC
c) 16 J/oC
d) 19 J/oC

Explanation: Average CP = 0.2*15 + 0.8*20 = 19 J/oC.

8. A mixture contains 30% Ar with CP = 30 J/oC, 30% N2 with CP = 20 J/oC and 40% CH4 with CP = 10 J/oC, what is the average CP of mixture?
a) 7 J/oC
b) 12 J/oC
c) 19 J/oC
d) 26 J/oC

Explanation: Average CP = 0.3*30 + 0.3*20 + 0.4*10 = 19 J/oC.

9. A mixture contains 20% O2 with CP = 10 J/oC, 30% N2 with CP = 20 J/oC and 50% CO2 with CP= 40 J/oC, what is the average CP of mixture?
a) 20 J/oC
b) 28 J/oC
c) 34 J/oC
d) 42 J/oC

Explanation: Average CP = 0.2*10 + 0.3*20 + 0.5*40 = 2 + 6 + 20 = 28 J/oC.

10. A mixture contains 20% SO2 with CP= 35 J/oC, 30% NO3 with CP = 20 J/oC and 50% CO2 with CP = 40 J/oC, what is the average CP of mixture?
a) 12 J/oC
b) 17 J/oC
c) 25 J/oC
d) 33 J/oC

Explanation: Average CP = 0.2*35 + 0.3*20 + 0.5*40 = 7 + 6 + 20 = 33 J/oC.

11. Heat Capacity of CO2 is given by 12 + 3T + T2, what is the enthalpy change from 0oC to 6oC?
a) 169 J
b) 198 J
c) 244 J
d) 360 J

Explanation: ∆H = 06 (12 + 3T + T2).dT = 12*6 + 3*36/2 + 63/3 = 198 J.

12. Heat Capacity of water is given by 4 + T2, what is the enthalpy change from 0oC to 3oC?
a) 7 J
b) 14 J
c) 21 J
d) 32 J

Explanation: ∆H = 03 (4 + T2).dT = 4*3 + 33/3 = 21 J.

13. CP-T curve covers 10 J from 2oC to 10oC, what is the enthalpy change?
a) 10 J
b) 20 J
c) 80 J
d) 100 J

Explanation: Enthalpy change is the area covered under CP-T curve.

14. CP-T curve of CO2 forms a rectangle of height 10 J/oC from 5oC to 10oC?
a) 10 J
b) 50 J
c) 100 J
d) 250 J

Explanation: Enthalpy change is the area covered under CP-T curve = Area of rectangle = 10*(10 – 5) = 50 J.

15. CP-T curve of H2 forms a rectangle of height 20 J/oC from 4oC to 5oC?
a) 20 J
b) 80 J
c) 100 J
d) 140 J 