JEE Chemistry Thermodynamics MCQs Set B

Question. Identify the correct statement regarding entropy
(a) At absolute zero temperature, entropy of a perfectly crystalline substance is taken to be zero
(b) At absolute zero temperature, the entropy of a perfectly crystalline substance is positive
(c) Absolute entropy of a substance cannot be determined
(d) At 0°C, the entropy of a perfectly crystalline substance is taken to be zero

Answer: A

Question. Unit of entropy is
(a) JK^–1 mol^–1
(b) J^–1 K^–1 mol^–1
(c) J mol^–1
(d) None of these

Answer: A

Question. In an exothermic reaction (reversible) which of the following has positive value?
(a) None of these
(b) Entropy
(c) Enthalpy
(d) Gibb’s free energy

Answer: A

Question. Which of the following pairs of a chemical reaction is certain to result in a spontaneous reaction?
(a) Exothermic and increasing disorder
(b) Exothermic and decreasing disorder
(c) Endothermic and increasing disorder
(d) Endothermic and decreasing disorder

Answer: A

Question. The enthalpy of fusion of water is 1.435 kCal/mol. The molar entropy change for the melting of ice at 0°C is :
(a) 5.260 cal / (mol K)
(b) 10.52 cal / (mol K)
(c) 21.04 cal / (mol K)
(d) 0.526 cal / (mol K)

Answer: A

Question. Read the following statements carefully and choose the correct option
(i) The state of the system is specified by state functions or state variables.
(ii) Variables like P, V and T are called state variables or state functions
(iii) Their values depend only on the state of the system and not on how it is reached.
(a) (i) , (ii) and (iii) are correct
(b) Only (iii) is correct
(c) (ii) and (iii) are correct
(d) (i) and (ii) are correct

Answer: C

Question. Read the following statements carefully and choose the correct option
(i) Internal energy, U, of the system is a state function.
(ii) –w shows, that work is done on the system.
(iii) +w shows, that work is done by the system
(a) Only (i) is correct
(b) (ii) and (iii) are correct
(c) (i) and (ii) are correct
(d) (i) and (iii) are correct

Answer: A

Question. Read the following statements carefully and choose the correct answer
(i) Expansion of a gas in vacuum (p_ex = 0) is called free expansion.
(ii) Work is done during free expansion of an ideal gas whether the process is reversible or irreversible
(iii) No work is done during free expansion of an ideal gas whether the process is reversible or irreversible
(iv) No work is done during free expansion of an ideal gas when the process is reversible
(a) Statements (i) and (iii) are correct
(b) Only statement (iii) is correct
(c) Statements (ii) and (iv) are correct
(d) Statements (i) and (iv) are correct

Answer: A

Question. Which of the following statement(s) is/are correct ?
(i) In case of expansion maximum amount of work can be obtained under isothermal conditions by reversibly carrying out the process rather than through irreversible route.
(ii) In case of compression, minimum amount of work can be done on system by carrying out the process irreversibly than reversibly.
(a) (i) and (ii)
(b) Only (ii)
(c) Only (i)
(d) Neither (i) nor (ii)

Answer: A

Question. Read the following statements carefully and choose the correct option
(i) In case of diatomic molecules the enthalpy of atomization is also the bond dissociation enthalpy.
(ii) In case polyatomic molecules, bond dissociation enthalpy is different for different bonds within the same molecule.
(a) Both (i) and (ii) are correct
(b) (i) is correct but (ii) is incorrect
(c) (ii) is correct but (i) is incorrect
(d) Both (i) and (ii) are incorrect

Answer: A

Question. Read the following statements regarding spontaneity of a process and mark the appropriate choice.
(i) When enthalpy factor is absent than randomness factor decides spontaneity of a process.
(ii) When randomness factor is absent then enthalpy factor decides spontaneity of a process.
(iii) When both the factors take place simultaneously, the magnitude of both the factors decide spontaneity of a process.
(a) Statements (i), (ii) and (iii) are correct.
(b) Statements (i), (ii) and (iii) are incorrect
(c) Statement (iii) is correct, (i) and (ii) are incorrect
(d) Statements (i) and (ii) are correct and (iii) is incorrect

Answer: A

Question. Which of the following statement is incorrect ?
(a) The standard state of solid iron at 298 K is pure iron at 1 bar
(b) The standard state of a substance at a specified temperature is its pure form at 1 bar
(c) The standard enthalpy of reaction is the enthalpy change for a reaction when all the participating substances are in their standard states.
(d) None of these

Answer: A

Question.
Assertion : T, P and V are state variables or state functions.
Reason : Their values depend on the state of the system and how it is reached.
(a) Assertion is correct, reason is incorrect
(b) Assertion is incorrect, reason is correct
(c) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(d) Assertion is correct, reason is correct; reason is a correct explanation for assertion

Answer: A

Question.
Assertion : At constant temperature and pressure whatever heat absorbed by the system is used in doing work.
Reason : Internal energy change is zero
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct

Answer: A

Question.
Assertion : Absolute value of internal energy of a substance cannot be determined.
Reason : It is impossible to determine exact values of constitutent energies of the substances
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct

Answer: A

Question.
Assertion : A process is called adiabatic if the system does not exchange heat with the surroundings.
Reason : It does not involve increase or decrease in temperature of the system.
(a) Assertion is correct, reason is incorrect
(b) Assertion is incorrect, reason is correct
(c) Assertion is correct, reason is correct; reason is a correct explanation for assertion
(d) Assertion is correct, reason is correct; reason is not a correct explanation for assertion

Answer: A

Question.
Assertion : Internal energy is an extensive property.
Reason : Internal energy depends upon the amount of the system.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is incorrect, reason is correct
(d) Assertion is correct, reason is incorrect

Answer: A

Question.
Assertion : There is exchange in internal energy in a cyclic process.
Reason : Cyclic proces is the one in which the sytem returns to its initial state after a number of reactions.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct

Answer: A

Question.
Assertion : The mass and volume of a substance are the extensive properties and are proportional to each other.
Reason : The ratio of mass of a sample to its volume is an intensive property.
(a) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(b) Assertion is correct, reason is correct; reason is a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct

Answer: A

Question.
Assertion : First law of thermodynamics is applicable to an electric fan or a heater.
Reason : In an electric fan, the electrical energy is converted into mechanical work that moves the blades. In a heater, electrical energy is converted into heat energy.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct

Answer: A

Question.
Assertion : The value of enthalpy of neutralization of weak acid and strong base is numerically less than 57.1 kJ.
Reason : All the OH^– ions furnished by 1 g equivalent of strong base are not completely neutralized
(a) Assertion is correct, reason is incorrect
(b) Assertion is incorrect, reason is correct
(c) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(d) Assertion is correct, reason is correct; reason is a correct explanation for assertion

Answer: A

Question.
Assertion : When a solid melts, decrease in enthalpy is observed.
Reason : Melting of a solid is endothermic.
(a) Assertion is incorrect, reason is correct
(b) Assertion is correct, reason is incorrect
(c) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(d) Assertion is correct, reason is correct; reason is a correct explanation for assertion

Answer: A

Question.
Assertion : An exothermic process which is nonspontaneous at high temperature may become spontaneous at a low temperature.
Reason : There occurs a decrease in entropy factor as the temperature is decreased.
(a) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(b) Assertion is correct, reason is incorrect
(c) Assertion is incorrect, reason is correct
(d) Assertion is correct, reason is correct; reason is a correct explanation for assertion

Answer: A

Question.
Assertion : Many endothermic reactions that are not spontaneous at room temperature become spontaneous at high temperature.
Reason : Entropy of the system increases with increase in temperature
(a) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(b) Assertion is correct, reason is incorrect
(c) Assertion is incorrect, reason is correct
(d) Assertion is correct, reason is correct; reason is a correct explanation for assertion

Answer: A

Question. A piston filled with 0.04 mol of an ideal gas expands reversibly from 50.0 mL to 375 mL at a constant temperature of 37.0ºC. As it does so, it absorbs 208 J of heat. The values of q and w for the process will be:
(R = 8.314 J/mol K) (ln 7.5 = 2.01)
(a) q = + 208 J, w = – 208 J
(b) q = – 208 J, w = – 208 J
(c) q = – 208 J, w = + 208 J
(d) q = + 208 J, w = + 208 J

Answer: A

Question. The internal energy change when a system goes from state A to B is 40 kJ/mole. If the system goes from A to B by a reversible path and returns to state A by an irreversible path what would be the net change in internal energy ?
(a) Zero
(b) > 40 kJ
(c) < 40 kJ
(d) 40 kJ

Answer: A

Question. Under isothermal condition for one mole of ideal gas what is the ratio of work done under reversible to irreversible process, initially held at 20 atm undergoes expansion from 1L to 2L, at 298K, under external pressure of 10 atm?
(a) 1.7
(b) 1.4
(c) 2.0
(d) 1.0

Answer: A

Question. What is the amount of heat (in Joules) absorbed by 18 g of water initially at room temperature heated to 100°C ? If 10g of Cu is added to this water , than decrease in temperature (in Kelvin) of water was found to be? C (p,m) for water 75.32J/mol K ; C (p,m) for Cu = 24.47J/mol K.
(a) 5649, 369
(b) 5278, 342
(c) 5544, 324
(d) 3425, 425

Answer: A

Question. What is the equilibrium constant if ATP hydrolysis by water produce standard free energy of –50 kJ/mole under normal body conditions ?
(a) 2.66 × 10⁸
(b) 1.18 × 10⁷
(c) 5.81 × 10⁸
(d) 1.98 × 10⁸

Answer: A