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#### Thermodynamics - Important Question Paper

11th Standard

Reg.No. :
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Chemistry

Time : 01:00:00 Hrs
Total Marks : 50

Part A

Multiple Choice Question

10 x 1 = 10
1. The enthalpies of formation of Al2O3 and Cr2Oare -1596 kJ and -1134 kJ, respectively. ΔH for the reaction 2AI + Cr2O3 ⟶ 2Cr + Al2O3 is

(a)

- 1365 kJ

(b)

2730 kJ

(c)

- 2730 kJ

(d)

- 462 kJ

2. Which of the following is not a thermodynamic function?

(a)

internal energy

(b)

enthalpy

(c)

entropy

(d)

frictional energy

3. The value of ΔH for cooling 2 moles of an ideal monatomic gas from 125° C to 25° C at constant pressure will be [given Cp=$\frac{5}{2}$R]

(a)

- 250 R

(b)

- 500 R

(c)

500 R

(d)

+ 250 R

4. Given that C(g)+ O2(g) ⟶ CO2(g)ΔHo =-akJ;2CO(g)+O2(g) ⟶ 2CO2(g)ΔHo=-bkJ; Calculate the AHo for the reaction C(g)+ 1/2O2(g) ⟶ CO(g)

(a)

$\frac{b+2a}{2}$

(b)

2a-b

(c)

$\frac{2a-b}{2}$

(d)

$\frac{b-2a}{2}$

5. When 15.68 litres of a gas mixture of methane and propane are fully combusted at 0° C and 1 atmosphere, 32 litres of oxygen at the same temperature and pressure are consumed. The amount of heat of released from this combustion in KJ is (ΔHc (CH4) = - 890 KJ mol-1 and ΔHc (C3H8 = - 2220 KJ mol-1)

(a)

- 889 K.Jmol-1

(b)

- 1390 K.Jmol-1

(c)

- 3180 K.Jmol-1

(d)

- 635.47 K.Jmol-1

6. The temperature of the system, decreases in an ---------

(a)

Isothermal expansion

(b)

Isothermal Compression

(c)

(d)

7. In an isothermal reversible compression of an ideal gas the sign of q, ΔS and ware respectively

(a)

+,-,-

(b)

-,+,-

(c)

+,-,+

(d)

-, -, +

8. A fundamental goal of thermodynamics is the prediction of ------ of the process.

(a)

reversibility

(b)

rate

(c)

spontaneity

(d)

none of these

9. A portion of matter under consideration, which is separated from rest of universe by real or imaginary boundaries is called-----

(a)

surroundings

(b)

system

(c)

boundary

(d)

Universe

10. Mathematically, the third law of thermodynamics is expressed as _______

(a)

$\overset{\lim}{T\rightarrow 0}{ S=0 }$

(b)

$\overset{\lim}{T\rightarrow \infty} {S=1 }$.

(c)

ΔU = q + w

(d)

G = H - TS

11. Part B

Answer all the Two Mark Questions

6 x 2 = 12
12. Give examples for extensive and intensive properties.

13. Define molar heat capacity at constant volume and molar heat capacity at constant pressure.

14. Explain why Cp is always greater than Cv?

15. Give expressions for the entropy change a-phase change.

16. Two litres of an ideal gas at a pressure of 10 atm expands isothermally into vacuum until its total volume is 10 litres. How much heat is absorbed and how much work is done in the expansion.

17. What is the aim of the study of chemical thermodynamics?

18. Part C

Answer all the Three  Mark Questions

6 x 3 = 18
19. Define the relationship Cp - Cv = nR for an ideal gas.

20. Show that $\Delta$U = nCv (T2 - T1) and $\Delta$H = nCp(T2 - T1).

21. Derive an expression for the efficiency of a heat engine.

22. 1g of graphite is burnt in a bomb calorimeter in excess of oxygen at 298K and 1 atm pressure according to the equation.
C(graphite) + O2(g)  $\rightarrow$ CO2(g)
During the reaction, temperature rises. from 298K to 299K. If the heat capacity of the bomb calorimeter is 20.7 kJ mol-1. What is the enthalpy change for the above reaction at 298K and 1 atm?

23. Enthalpies of formation of CO(g),CO2(g), N2O(g) and N2O4(g) are -110, -393, + 81 and + 9.7 kJ mol respectively. Find the value of $\Delta$H for the reaction. N2O4(g) + 3CO(g) $\rightarrow$ N2O(g) + 3CO2(g).

24. Given N2(g) + 3H2(g) $\rightarrow$ 2NH3(g); $\Delta$H°=-92.4 kJ mol-1. What is the standard enthalpy of formation of NH3(g)?

25. Part D

Answer all the Five  Mark Questions

2 x 5 = 10
26. Calculate ΔG0 for the reaction. CO(g)+ $\\ \frac { 1 }{ 2 }$O2(g) ⟶ CO2(g), ΔH0 = - 282.84 kJ Given, S0(C02) =213.8Jk-1 mol-1, So (CO) = 197.9 Jk-1 mol-1 S0(O2) = 205.0 Jk-1 mol-1