Specific Heat and Molar Specific Heat of a Gas

Specific Heat and Molar Specific Heat of a Gas MDCAT MCQs with answers

11 past paper MCQs on Specific Heat and Molar Specific Heat of a Gas, from the Thermodynamics unit of MDCAT Physics. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.

Read the notes first Practise the unit as a quiz

1.Which of the following has highest specific heat capacity? (NUMS MDCAT 2025)

  1. Copper
  2. Iron
  3. Water
  4. Glass
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Correct answer: (c) Water

Water has an unusually high specific heat, about $4200\,\mathrm{J\,kg^{-1}\,K^{-1}}$.

2.The specific heat of a gas in adiabatic process is: (PMC MDCAT 2022)

  1. Zero
  2. Infinite
  3. Negative
  4. Remains constant
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Correct answer: (a) Zero

No heat is exchanged in an adiabatic change, so the heat per degree is zero.

3.Molar heat capacity at constant pressure is given by: (PMC MDCAT 2022)

  1. dQ/dV
  2. dQ/dT
  3. dU/dT
  4. dU/dV
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Correct answer: (b) dQ/dT

Molar heat capacity is the heat needed per mole for each degree of temperature rise.

4.Given that the Cv of a gas is 8 J/K mol, calculate the change in heat for dT=50K of 2 mole gas? (PMC MDCAT 2022)

  1. 800J
  2. 1631.4J
  3. 1700J
  4. 1800J
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Correct answer: (a) 800J

$Q=nC_v\Delta T=2\times8\times50$, which is $800\,\mathrm{J}$.

5.Molar heat capacity at constant volume is given by: (PMC MDCAT 2022)

  1. dQ/dN
  2. dQ/dP
  3. dU/dT
  4. dU/dV
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Correct answer: (c) dU/dT

At constant volume no work is done, so the heat per mole per degree is $dU/dT$.

6.Heat capacity is defined as _______ required to change the temperature of substance by_______ (PMC MDCAT 2022)

  1. Momentum, 1 degree C
  2. Heat, 1 degree C
  3. Heat, 2 degree C
  4. Work, 2 degree C
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Correct answer: (b) Heat, 1 degree C

Heat capacity is the heat needed to raise the temperature of the body by one degree.

7.Molar heat capacity is defined as heat required to raise the temperature by 1 degree of ____ substance. (PMC MDCAT 2022)

  1. 2 mole
  2. 2 kg
  3. 1 kg
  4. 1 mole
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Correct answer: (d) 1 mole

Molar heat capacity is the heat needed to raise one mole by one degree.

8.Specific heat of gas in isothermal process is: (PMC MDCAT 2022)

  1. Infinite
  2. Zero
  3. Negative
  4. Remain constant
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Correct answer: (a) Infinite

Heat is taken in with no rise in temperature, so the heat per degree is unbounded.

9.Unit of heat capacity is: (PMC MDCAT 2022)

  1. J/K
  2. J/K.mole
  3. J/K.kg
  4. Joule
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Correct answer: (a) J/K

Heat capacity is heat per degree, that is joules per kelvin.

10.Which of the following cases (if any) requires the greatest amount of heat? (In each case the material is the same) (PMC Practice 2021)

  1. 1.5 kg of the material is to be heated by 7.0 C0
  2. 3.0 kg of the material is to be heated by 3.5 C0
  3. 0.50 kg of the material is to be heated by 2 1 C0
  4. The amount of heat required is the same in each of the three previous case
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Correct answer: (d) The amount of heat required is the same in each of the three previous case

$Q=mc\Delta T$, and $1.5\times7$, $3.0\times3.5$ and $0.5\times21$ are all $10.5$.

11.A liquid has mass m and specific heat capacity c. The rate of change in temperature of the liquid is R. What is the rate at which heat is transferred from the liquid. (PMC Practice 2021)

  1. Rmc
  2. R/me
  3. me/R
  4. Rm/c
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Correct answer: (a) Rmc

$Q=mc\Delta T$, so the rate of heat loss is $mcR$.

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