NEET Thermodynamics PYQ practice sheet

16 previous-year NEET Chemistry questions from Thermodynamics, newest papers first. Thermodynamics carries 16 of the Chemistry questions in NEET 2020 to 2026, so this is a good place to test yourself after revising the chapter. Marking: +4 correct, −1 wrong.

1. 1.

   RE-NEET 2026

   Two moles of an ideal gas undergo free expansion from $10$ L to $100$ L at $300$ K. The values of $\Delta S_{system}$ and $\Delta S_{surroundings}$ are ($R$ is universal gas constant)

   • (A)
     $\Delta S_{system} = 0;\ \Delta S_{surroundings} = 0$
   • (B)
     $\Delta S_{system} = 0;\ \Delta S_{surroundings} = 4.606\,R$
   • (C)
     $\Delta S_{system} = 4.606\,R;\ \Delta S_{surroundings} = -4.606\,R$
   • (D)
     $\Delta S_{system} = 4.606\,R;\ \Delta S_{surroundings} = 0$
2. 2.

   RE-NEET 2026

   Consider the reversible processes for $1.0$ mol of an ideal gas as shown in the figure. Figure: a $P$-$V$ cycle with four reversible steps: process $1$ is an isothermal expansion at $T_1$ from $(p_1, V_1)$ to $(p_2, V_2)$; process $2$ is an adiabatic expansion from $(p_2, V_2, T_1)$ to $(p_3, V_3, T_2)$; process $3$ is an isothermal compression at $T_2$ from $(p_3, V_3)$ to $(p_4, V_4)$; process $4$ is an adiabatic compression from $(p_4, V_4, T_2)$ back to $(p_1, V_1, T_1)$. Processes $2$ and $4$ are adiabatic. $w_1$, $w_2$, $w_3$ and $w_4$ represent work done (in calories) in the processes 1, 2, 3 and 4, respectively; $\Delta U_2$ and $\Delta U_4$ are changes in the internal energy for the processes 2 and 4, respectively. [use $R = 2\ \mathrm{cal\,K^{-1}\,mol^{-1}}$] The correct option is

   • (A)
     $w_1 + w_3 = -2T_1\ln\frac{V_2}{V_1} - 2T_2\ln\frac{V_4}{V_3}$
   • (B)
     $w_1 + w_2 = 2T_1\ln\frac{V_2}{V_1}$
   • (C)
     $w_2 + w_4 = \Delta U_2 - \Delta U_4$
   • (D)
     $w_1 + w_2 + w_3 + w_4 = 0$
3. 3.

   RE-NEET 2026

   A protein undergoes reversible thermal denaturation from its initial state $\mathbf{N}$ to denatured state $\mathbf{D}$ according to $\mathbf{N} \rightleftharpoons \mathbf{D}$. At $60^\circ$C, the concentrations of both $\mathbf{N}$ and $\mathbf{D}$ are equal at equilibrium, and the standard enthalpy change of denaturation is $666\ \mathrm{kJ\,mol^{-1}}$. The standard entropy change ($\Delta S^\circ$ in $\mathrm{kJ\,K^{-1}\,mol^{-1}}$) of the protein upon denaturation at $60^\circ$C is closest to

   • (A)
     $11.1$
   • (B)
     $333.0$
   • (C)
     $2000.0$
   • (D)
     $2.0$
4. 4.

   NEET 2026

   Consider the following reaction: $\mathrm{2A(g)+B(g)\to2D(g)}$ $\Delta U^\circ=-10\ \text{kJ mol}^{-1}$ and $\Delta S^\circ=-44\ \text{J K}^{-1}$ at 298 K. Identify the correct option with $\Delta G^\circ$ for the reaction and spontaneity of the reaction at 298 K. (Given: $R=8.31\ \text{J mol}^{-1}\text{K}^{-1}$)

   • (A)
     $+0.63568\ \text{kJ mol}^{-1}$, non-spontaneous
   • (B)
     $+1.635\ \text{kJ mol}^{-1}$, non-spontaneous
   • (C)
     $-1.635\ \text{kJ mol}^{-1}$, spontaneous
   • (D)
     $-0.63568\ \text{kJ mol}^{-1}$, spontaneous
5. 5.

   NEET 2026

   At a certain temperature, $T$ (K), during a process, 500 J is absorbed by the system and work of 200 J is done by the system. Then change in internal energy of the system is:

   • (A)
     300 J
   • (B)
     500 J
   • (C)
     400 J
   • (D)
     700 J
6. 6.

   NEET 2024

   Match List-I with List-II. List-I (Process): (A) Isothermal process, (B) Isochoric process, (C) Isobaric process, (D) Adiabatic process List-II (Conditions): (I) No heat exchange, (II) Carried out at constant temperature, (III) Carried out at constant volume, (IV) Carried out at constant pressure Choose the correct answer from the options given below:

   • (A)
     A-I, B-II, C-III, D-IV
   • (B)
     A-IV, B-III, C-II, D-I
   • (C)
     A-II, B-III, C-IV, D-I
   • (D)
     A-IV, B-II, C-III, D-I
7. 7.

   NEET 2024

   In which of the following processes entropy increases? A. A liquid evaporates to vapour. B. Temperature of a crystalline solid lowered from 130 K to 0 K. C. $\mathrm{2NaHCO_3(s)\to Na_2CO_3(s)+CO_2(g)+H_2O(g)}$ D. $\mathrm{Cl_2(g)\to2Cl(g)}$ Choose the correct answer from the options given below:

   • (A)
     A, C and D
   • (B)
     C and D
   • (C)
     A, B and D
   • (D)
     A and C
8. 8.

   NEET 2024

   The work done during reversible isothermal expansion of one mole of hydrogen gas at $25^\circ$C from pressure of 20 atmosphere to 10 atmosphere is: (Given $R=2.0\ \mathrm{cal\ K^{-1}mol^{-1}}$)

   • (A)
     –413.14 calories
   • (B)
     413.14 calories
   • (C)
     0 calorie
   • (D)
     100 calories
9. 9.

   NEET 2023

   The equilibrium concentrations of the species in the reaction $\mathrm{A + B \rightleftharpoons C + D}$ are $2,\ 3,\ 10$ and $6\ \mathrm{mol\,L^{-1}}$, respectively at $300\ \mathrm{K}$. $\Delta G^\circ$ for the reaction is ($R = 2\ \mathrm{cal/mol\,K}$)

   • (A)
     $-13.73\ \mathrm{cal}$
   • (B)
     $1372.60\ \mathrm{cal}$
   • (C)
     $-137.26\ \mathrm{cal}$
   • (D)
     $-1381.80\ \mathrm{cal}$
10. 10.

    NEET 2023

    Which amongst the following options is the correct relation between change in enthalpy and change in internal energy?

    • (A)
      $\Delta H + \Delta U = \Delta nR$
    • (B)
      $\Delta H = \Delta U - \Delta n_g RT$
    • (C)
      $\Delta H = \Delta U + \Delta n_g RT$
    • (D)
      $\Delta H - \Delta U = -\Delta nRT$
11. 11.

    NEET 2022

    Which of the following p-V curve represents maximum work done?

    • (A)
      a steep isothermal curve falling sharply over a narrow volume range
    • (B)
      a closed elliptical isothermal loop
    • (C)
      a gently falling isothermal curve spanning a wide volume range
    • (D)
      a vertical isothermal line (no change in volume)
12. 12.

    NEET 2021

    Which one among the following is the correct option for right relationship between $C_P$ and $C_V$ for one mole of ideal gas ?

    • (A)
      $C_P + C_V = R$
    • (B)
      $C_P = RC_V$
    • (C)
      $C_V = RC_P$
    • (D)
      $C_P - C_V = R$
13. 13.

    NEET 2021

    For irreversible expansion of an ideal gas under isothermal condition, the correct option is :

    • (A)
      $\Delta U \neq 0,\ \Delta S_{total} = 0$
    • (B)
      $\Delta U \neq 0,\ \Delta S_{total} \neq 0$
    • (C)
      $\Delta U = 0,\ \Delta S_{total} = 0$
    • (D)
      $\Delta U = 0,\ \Delta S_{total} \neq 0$
14. 14.

    NEET 2020

    Hydrolysis of sucrose is given by the following reaction. Sucrose $+\ \mathrm{H_2O} \rightleftharpoons$ Glucose $+$ Fructose. If the equilibrium constant ($K_c$) is $2\times10^{13}$ at $300$ K, the value of $\Delta_rG^\ominus$ at the same temperature will be :

    • (A)
      $-8.314\ \mathrm{J\,mol^{-1}K^{-1}}\times300\ \mathrm{K}\times\ln(2\times10^{13})$
    • (B)
      $8.314\ \mathrm{J\,mol^{-1}K^{-1}}\times300\ \mathrm{K}\times\ln(2\times10^{13})$
    • (C)
      $8.314\ \mathrm{J\,mol^{-1}K^{-1}}\times300\ \mathrm{K}\times\ln(3\times10^{13})$
    • (D)
      $-8.314\ \mathrm{J\,mol^{-1}K^{-1}}\times300\ \mathrm{K}\times\ln(4\times10^{13})$
15. 15.

    NEET 2020

    For the reaction, $2\mathrm{Cl(g)} \rightarrow \mathrm{Cl_2(g)}$, the correct option is :

    • (A)
      $\Delta_rH>0$ and $\Delta_rS>0$
    • (B)
      $\Delta_rH>0$ and $\Delta_rS<0$
    • (C)
      $\Delta_rH<0$ and $\Delta_rS>0$
    • (D)
      $\Delta_rH<0$ and $\Delta_rS<0$
16. 16.

    NEET 2020

    The correct option for free expansion of an ideal gas under adiabatic condition is :

    • (A)
      $q=0$, $\Delta T=0$ and $w=0$
    • (B)
      $q=0$, $\Delta T<0$ and $w>0$
    • (C)
      $q<0$, $\Delta T=0$ and $w=0$
    • (D)
      $q>0$, $\Delta T>0$ and $w>0$