250+ TOP MCQs on Thermodynamics Applications and Answers

Chemistry Multiple Choice Questions on “Thermodynamics Applications”.

1. When an ideal gas is compressed in a piston using 5 atm of pressure through a 50-metre cube of volume, what is the amount of work done?
a) 10 Newton metre
b) 0.1 Newton metre
c) 250 Newton metre
d) 55 Newton metre
Answer: c
Clarification: When a pressure P is exerted through a volume V the work done is given by P ΔV, so here pressure is 5 atm and volume is a 50-metre cube. The work that is done is 5 atm X 50-metre cube = 250 Newton metre.

2. When the pressure of 3 atm is exerted over a surface area of a 10-metre square, what is a force that is applied?
a) 30 Newton
b) 3.33 Newton
c) 0.33 Newton
d) 0.3 Newton
Answer: a
Clarification: Force is defined as the product of pressure and the surface area so here as pressure is 3 atm and surface area is 10-metre square. The force that is applied equals 3 atm x 10-metre square = 30 Newton.

3. Expansion of gas under zero pressure is free expansion.
a) True
b) False
Answer: a
Clarification: The expansion of a gas in a vacuum without pressure is called free expansion. During the free expansion of gas, the work is not done whether the process is reversible or Irreversible. So the above statement is considered to be true.

4. 6 litres of an ideal gas expands isothermally at a temperature of 300 Kelvin up to 10 litres at a pressure of 5 atm, what is the work done?
a) 30 Newton metre
b) 80 Newton metre
c) 50 Newton metres
d) 20 Newton metre
Answer: d
Clarification: The expression for work done is given by pressure x volume difference, here an ideal gas has a volume difference of 4 litres at 5 ATM pressure. So the work done = 10 – 6 liters x 5atm = 20 Newton metre.

5. Which of the following is an intensive property?
a) Volume
b) Colour
c) Enthalpy
d) Internal energy
Answer: b
Clarification: An intensive property does not depend on the quantity or size of the object, whereas extensive property depends on the quantity and size of the object. Here volume, enthalpy and internal energy are extensive properties, while colour is an intensive property.

6. The value of the product of a universal gas constant and the temperature difference is given by 10 kJ/mol at 1 mole and the internal energy is given by 20 KJ, what is the enthalpy of this system in KJ?
a) 30
b) 10
c) 20
d) 200
Answer: a
Clarification: We know that ΔH = ΔU + nRΔT; where ΔH is the enthalpy, ΔU is the internal energy, n is the number of moles, R is the universal gas constant and ΔT is the temperature difference. So enthalpy is 10 KJ + 20KJ = 30 KJ.

7. What is the difference in heat capacities at constant volume and pressure?
a) Universal volume constant
b) Universal gas constant
c) Universal pressure constant
d) Universal temperature constant
Answer: b
Clarification: We all know that ΔH = ΔU + nRΔT; ΔH = nC_PΔT and ΔU = nC_vΔT; ΔH – ΔU = nC_PΔT – nC_vΔT = n(C_P – C_V) ΔT. By equating L.H.S. and R.H.S., we get n(C_P – C_V) ΔT = nRΔT; C_P – C_V = R. Hence it’s proven that difference of heat capacities at constant volume and pressure is the universal gas constant.

8. Write temperature difference in terms of heat capacity and heat energy?
a) ΔT = q/C
b) ΔT = qC
c) ΔT = C/q
d) ΔT = qm/C
Answer: a
Clarification: As we know that q = CΔT, where q is the heat energy, C is the specific heat and ΔT is the temperature difference, When the temperature difference is expressed in terms of the heat capacity and heat energy, it is given as ΔT = q/C.

9. If gas is expanded freely from 1 litre to 5 litres at a temperature of 60-degree centigrade what is the work done?
a) Positive
b) Negative
c) 0
d) Infinity
Answer: c
Clarification: When gas is expanded freely in a vacuum there is zero pressure exerted. The formula for work done is given by pressure X change in volume = 0 x 4. So the work done is zero in the process of free expansion.

10. The specific heat at constant pressure is given by the expression ____________
a) C_V = dq/dT
b) C_P = dq/dT
c) C_V = dqdt
d) C_P = dq/dt
Answer: b
Clarification: As we know that dq = CdT; where q is the heat energy, C is the specific heat and T is the temperature. At constant pressure, specific heat is given as C_P. The specific heat at constant pressure is given by the expression C_P = dq/dt.