MCQs on Thermodynamics for NEET & JEE Q1. What will be the value of ΔH, if the forward and reverse reactions have the same energy of act...

## MCQs on Thermodynamics for NEET & JEE

Q1. What will be the value of ΔH, if the forward and reverse reactions have the same energy of activation?

• (a) ΔH = ΔG = ΔS = 0
• (b) ΔS = 0
• (c) ΔG = 0
• (d) ΔH = 0

Q2. Choose the correct answer. A thermodynamic state function is a quantity

• (a) used to determine heat changes
• (b) whose value is independent of path
• (c) used to determine pressure volume work
• (d) whose value depends on temperature only.

Solution.

(b): State function is a property of the system whose value depends only upon the state of the system and is independent of the path or the manner by which the state is reached.

Q3. For the process to occur under adiabatic conditions, the correct condition is

• (a) ΔT = 0
• (b) Δp = 0
• (c) g = 0
• (d) w=0

Solution.

(c): Adiabatic system does not exchange heat with the surroundings.

Q4. What is the molar entropy change for melting of ice at 0, if ΔHf = 1.435 kcal/mol?

• (a) 0.526 cal/(mol K)
• (b) 5.26 cal/(mol K)
• (c) 10.52 cal/(mol K)
• (d) 21.04 cal/(mol K)

Q5. What is the function of a catalyst in a chemical reaction?

• (a) decrease rate constant of reaction
• (b) increases activation energy of reaction
• (c) reduces enthalpy of reaction
• (d) does not affect the equilibrium constant of reaction

Q6. What will be the work done by 3 moles of an ideal gas when it expands spontaneously in a vacuum?

• (a) zero
• (b) infinite
• (c) 3 joules
• (d) 9 joules

Q7. Find the temperature at which the below reaction will be in equilibrium if the enthalpy and entropy change for the reaction is 30 kJ mol-1 and 105 J K-1 mol-1 respectively

Br2(l) + Cl2(g) → 2BrCl(g)

• (a) 273 K
• (b) 300 K
• (c) 450 K
• (d) 285.7 K

Q8. Which is true for the entropy of a spontaneous reaction?

• (a) ΔS(system) – ΔS(surroundings) > 0
• (b) ΔS(system) + ΔS(surroundings) > 0
• (c) ΔS(surroundings) > 0 only
• (d) ΔS(system) > 0 only

Q9. An ideal gas is expanded isothermally at 300 K from 1 litre to 10 litres. Find the ΔE for this process (R = 2 cal mol-1 K-1)

• (a) 9 L atm
• (b) 1381.1 cal
• (c) zero
• (d) 163.7 cal

Q10. ΔH for the reaction N2 + 3H2 2NH3

• (a) ΔE – 2RT
• (b) ΔE + 2RT
• (c) ΔE – RT
• (d) ΔH = RT

Q11. The enthalpies of all elements in their standard states are

• (a) unity
• (b) zero
• (c) <0
• (d) different for each element.

Solution.

(b) : By convention, the standard enthalpy of formation of every element in its standard state is zero.

Q12. ΔU° of combustion of methane is – X kJ mol-1. The value of ΔH° is

• (a) = ΔU°
• (b) >ΔU°
• (c) <ΔU°
• (d) =0

Solution.

(c) : CH4(g)+2O2 → CO2(g)+2H2O(l)

Δn = 1 – 3 = -2.

ΔH° = ΔU° + ΔnRT = -X- 2RT

Q13. The enthalpy of combustion of methane, graphite and dihydrogen at 298 K are, -890.3 kJ mol-1,-393.5 kJ mol-1 and-285.8 kJ mol-1 respectively. Enthalpy of formation of CH4(g) will be

• (a) -74.8 kJ mol-1
• (b) -52.27 kJ mol-1
• (c) +74.8 kJ mol-1
• (d) +52.26 kJ mol-1

Solution.

Q14. A reaction, A + B → C + D + q is found to have a positive entropy change. The reaction will be

• (a) possible at high temperature
• (b) possible only at low temperature
• (c) not possible at any temperature
• (d) possible at any temperature

Solution.

(d): A + B → C + D + q, ΔS = +ve

Here, ΔH = -ve

ΔG = ΔH – TΔS

For reaction to be spontaneous, ΔG should be -ve. As ΔH = -ve and ΔS is +ve, ΔG will be -ve at any temperature.

Q15. In a process, 701 J of heat is absorbed by a system and 394 S of work is done by the system. What is the change in internal energy for the process?

Solution.

Heat absorbed by the system (q) = 701 J

Work done by the system (w) = -394 J

According to first law of thermodynamics,

ΔU = q + w = 701 + (-394) = 701 – 394 = 307 J

Q16. Consider the following statements

(Assertion) The internal energy of an ideal gas does not change during an Isothermal process

(Reason) The decrease in the volume of the gas is compensated by a corresponding increase in pressure when its temperature is constant in accordance with Boyle law

• a. Both A & R are true and R is correct Explanation of A
• b. Both A & R are true and R is not correct Explanation of A
• c. A is true R is false
• d. A is false but R is true
Solution: (a)

### MCQs on First Law of Thermodynamics and Hess Law

Q1. The variations in enthalpy that can not be detected per calorimeter can be detected with the aid of

• Newton’s law
• Hess’s law
• Krebs law
• Ohm’s law

Q2. The energy required to sever a given covalent bond is named

• bond energy
• bond enthalpy
• bond dissociation energy
• all of above

Q3. Changes in enthalpy in an exothermic reaction is

• positive
• negative
• constant
• neutral

Q4. The first law of thermodynamics states that energy can not be

• created only
• destroyed only
• converted
• created and destroyed

Q5. Hess’s law states that a chemical reaction is independent of the route by which chemical reactions takes place while keeping the same

• initial conditions only
• final conditions only
• mid-conditions
• initial and final conditions

Q6. The standard enthalpy change of neutralization involves the reaction of an acid with an alkali to form 1 mol of

• water
• oxygen
• nitrogen
• anhydrous salt

Q7. The change in the energy between a chemical reaction and the surroundings at constant temperature is called

• enthalpy change
• enthalpy
• enthalpy profile
• dynamic enthalpy

Q8. To initiate a reaction the minimum energy which is required to break bonds is called

• bond energy
• activation energy
• breaking energy
• ionization energy

Q9. The standard condition for enthalpy changes are

• the pressure of 100 kPa
• temperature 298K
• normal physical state
• all of above

Q10. The application of law of thermodynamics to the enthalpy change was done by

• Newton
• Hess’s
• Lewis
• Sophocles

### MCQs on 2nd and 3rd Law of Thermodynamics and Entropy

Q1. Which of the following processes is used to do maximum work done on the ideal gas that is compressed to half of its initial volume?

• isothermal
• isochoric
• isobaric

Q2. What is the ratio of Cp/Cv for gas if the pressure of the gas is proportional to the cube of its temperature and the process is an adiabatic process?

• 2
• 3/2
• 4/3
• 5/3

Q3. The coefficient performance of a refrigerator is 5. Calculate the heat rejected to the surrounding if the temperature inside the freezer is -20 oC

• 11oC
• 41oC
• 21oC
• 31oC

Q4. What is a necessary condition for a reaction to be spontaneous at all temperatures?

• 𐤃H < 𐤃G
• 𐤃G and H should be positive
• 𐤃H = 𐤃G = 0
• 𐤃G and 𐤃H should be negative

Q5. Which of the following factor affects the heat of reaction based on Kirchhoff equation?

• molecularity
• temperature
• pressure
• volume

Q6. Chemical dissociation is

• exothermic
• reversible
• endothermic
• reversible and endothermic

Q7. Which of the following is the largest unit of energy?

• electron volt
• joule
• calorie
• erg

Q8. A perfect black body has a unique characteristic feature as

• a good absorber only
• a good absorber and a good radiator
• neither a radiator nor an absorber

Q9. A thermodynamic process where no heat is exchanged with the surroundings is

• isothermal
• isobaric
• isotropic

Q10. Which of the following laws was formulated by Nernst?

• First law of thermodynamics
• Second law of thermodynamics
• Third law of thermodynamics
• None of the above Name

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Advanced Chemistry: MCQs on Thermodynamics for NEET & JEE -1
MCQs on Thermodynamics for NEET & JEE -1
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