Thermodynamics question and answers 2023/24 update

Thermodynamics question and answers 2023/24 update Question 1. Hesss law is an application of (a) 1st law of Thermodynamics (b) 2nd law of Thermodynamics (c) Entropy change (d) ∆H = ∆U + P∆V. Question 2. 5 mole of an ideal gas expand isothermally and irreversibly from a pressure of 10 atm to 1 atm against a constant external pressure of 1 atm. Wirr at 300 K is: (a) -15.921 kJ (b) -11.224 kJ (c) -110.83 kJ (d) None of these Question 3. At absolute zero the entropy of a perfect crystal is zero. This statement corresponds to which law of thermodynamics? (a) Zeroth Law (b) First Law (c) Second Law (d) Third Law Question 4. Which of the following has the highest entropy? (a) Mercury (b) Hydrogen (c) Water (d) Graphite Question 5. An ideal gas is taken through the cycle A → B → C → A as shown in figure. If the net heat supplied to the gas in cycle is 5 J, the work done by the gas in the process C → A. (a) -5 J (b) -15 J (c) -10 J (d) -20 J Question 6. One mole of which of the following has the highest entropy? (a) Liquid Nitrogen (b) Hydrogen Gas (c) Mercury (d) Diamond Question 7. An ideal gas is taken around the cycle ABCA as shown in P-V diagram The next work done by the gas during the cycle is equal to: (a) 12P1V1 (b) 6P1V1 (c) 5P1V1 (d) P1V1 Question 8. Third law of thermodynamics provides a method to evaluate which property? (a) Absolute Energy (b) Absolute Enthalpy (c) Absolute Entropy (d) Absolute Free Energy Question 9. Which of the following is/are a reason that water is a desirable heat sink for use in calorimeters? I) Waters heat specific capacity is very precisely known. II) Water is readily available. III) Water has an unusually large specific heat capacity. (a) I only (b) I and II (c) I, II and III (d) II only Question 10. In a chemical reaction the bond energy of reactants is more than the bond energy of the products. Therefore, the reaction is (a) Exothermic (b) Athermic (c) Endothermic (d) Endergonic Question 11. In a reversible process the system absorbs 600 kJ heat and performs 250 kJ work on the surroundings. What is the increase in the internal energy of the system? (a) 850 kJ (b) 600 kJ (c) 350 kJ (d) 250 kJ Question 12. Which of the following neutralisation reactions is most exothermic? (a) HCl and NaOH (b) HCN and NaOH (c) HCl and NH4OH (d) CH3COOH and NH4OH Question 13. A student runs a reaction in a closed system. In the course of the reaction, 64.7 kJ of heat is released to the surroundings and 14.3 kJ of work is done on the system. What is the change in internal energy (∆U) of the reaction? (a) -79.0 kJ (b) 50.4 kJ (c) 79.0 kJ (d) -50.4 kJ Question 14. Identify the correct statement from the following in a chemical reaction. (a) The entropy always increases (b) The change in entropy along with suitable change in enthalpy decides the fate of a reaction (c) The enthalpy always decreases (d) Both the enthalpy and the entropy remain constant Question 15. 2 mole of an ideal gas at 27° C expands isothermally and reversibly from a volume of 4 litres to 40 litre. The work done (in kJ) is: (a) w = -28.72 kJ (b) w = -11.488 kJ (c) w = -5.736 kJ (d) w = -4.988 kJ Question 16. The latent heat of vapourization of ε liquid at 500 K and 1 atm pressure is 10.0 kcal/mol. What will be the change in internal energy (ΔU) of 3 moles of liquid at the same temperature (a) 13.0 kcal/mol (b) −13.0 kcal/mol (c) 27.0 kcal Question 17. Calculate the heat required to make 6.4 Kg CaC2 from CaO(s) and C(s) from the reaction: CaO(s) + 3 C(s) → CaC2(s) + CO (g) given that ∆f H° (CaC2) = -14.2 kcal. ∆f H° (CO) = -26.4 kcal. (a) 5624 kca (b) 1.11 × 104 kcal (c) 86.24 × 10³ (d) 1100 kcal Question 18. Entropy of the universe is (a) Continuously Increasing (b) Continuously Decreasing (c) Zero (d) Constant Question 19. At absolute zero the entropy of a perfect crystal is zero. This statement corresponds to which law of thermodynamics? (a) Zeroth Law (b) First Law (c) Second Law (d) Third Law Question 20. The bond energy (in kcal mol-1) of a C-C single bond is approximately (a) 1 (b) 10 (c) 83-85 (d) 1000 Answer