NEET Kinetic Theory PYQ practice sheet

10 previous-year NEET Physics questions from Kinetic Theory, newest papers first. Kinetic Theory carries 11 of the Physics 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

   The mean free path of molecules in an ideal gas $A$ is half that of another ideal gas $B$. The diameter of the spherical molecules of gas $A$ is twice the diameter of the molecules of $B$. If number densities of the gases $A$ and $B$ are $n_A$ and $n_B$, respectively, the correct option is:

   • (A)
     $n_A = 2n_B$
   • (B)
     $n_A = n_B$
   • (C)
     $n_A = \frac{1}{4}n_B$
   • (D)
     $n_A = \frac{1}{2}n_B$
2. 2.

   RE-NEET 2026

   An ideal gas is made of polyatomic molecules. Each of the molecules has three translational, three rotational and $f$ number of vibrational modes. If the ratio of heat capacities $C_P/C_V$ of the gas is $8/7$, then the value of $f$ is:

   • (A)
     $3$
   • (B)
     $1$
   • (C)
     $2$
   • (D)
     $4$
3. 3.

   NEET 2026

   A flask contains argon and chlorine in the ratio of 2 : 1 by mass. The temperature of the mixture is $27^\circ$C. The ratio of root mean square speed of the molecules of the two gases $\left(\dfrac{V^{\text{Ar}}_{\text{rms}}}{V^{\text{Cl}}_{\text{rms}}}\right)$ is: (Atomic mass of argon = 40.0 u and molecular mass of chlorine = 70.0 u)

   • (A)
     $\dfrac{2}{\sqrt7}$
   • (B)
     $\dfrac{\sqrt7}{2}$
   • (C)
     $\dfrac72$
   • (D)
     $\dfrac74$
4. 4.

   NEET 2024

   The following graph represents the T-V curves of an ideal gas (where T is the temperature and V the volume) at three pressures $P_1$, $P_2$ and $P_3$ compared with those of Charles's law represented as dotted lines. The graph has $T$ on the vertical axis and $V$ on the horizontal axis. Three curves for $P_1$, $P_2$ and $P_3$ are drawn with the $P_1$ curve steepest and the $P_3$ curve least steep, each close to a dotted Charles's-law line.

   • (A)
     $P_1>P_3>P_2$
   • (B)
     $P_2>P_1>P_3$
   • (C)
     $P_1>P_2>P_3$
   • (D)
     $P_3>P_2>P_1$
5. 5.

   NEET 2023

   The temperature of a gas is $-50^\circ\mathrm{C}$. To what temperature the gas should be heated so that the rms speed is increased by 3 times?

   • (A)
     $223\ \mathrm{K}$
   • (B)
     $669^\circ\mathrm{C}$
   • (C)
     $3295^\circ\mathrm{C}$
   • (D)
     $3097\ \mathrm{K}$
6. 6.

   NEET 2022

   The volume occupied by the molecules contained in 4.5 kg water at STP, if the intermolecular forces vanish away, is:

   • (A)
     $5.6\ \text{m}^3$
   • (B)
     $5.6\times10^{6}\ \text{m}^3$
   • (C)
     $5.6\times10^{3}\ \text{m}^3$
   • (D)
     $5.6\times10^{-3}\ \text{m}^3$
7. 7.

   NEET 2021

   Match Column - I and Column - II and choose the correct match from the given choices.

   • (A)
     (A) - (R), (B) - (Q), (C) - (P), (D) - (S)
   • (B)
     (A) - (Q), (B) - (R), (C) - (S), (D) - (P)
   • (C)
     (A) - (R), (B) - (P), (C) - (S), (D) - (Q)
   • (D)
     (A) - (Q), (B) - (P), (C) - (S), (D) - (R)
8. 8.

   NEET 2020

   The mean free path for a gas, with molecular diameter $d$ and number density $n$ can be expressed as :

   • (A)
     $\frac{1}{\sqrt2\, n\pi d}$
   • (B)
     $\frac{1}{\sqrt2\, n\pi d^2}$
   • (C)
     $\frac{1}{\sqrt2\, n^2\pi d^2}$
   • (D)
     $\frac{1}{\sqrt2\, n^2\pi^2 d^2}$
9. 9.

   NEET 2020

   A cylinder contains hydrogen gas at pressure of $249$ kPa and temperature $27^\circ$C. Its density is : ($R = 8.3$ J mol$^{-1}$ K$^{-1}$)

   • (A)
     0.5 kg/m$^3$
   • (B)
     0.2 kg/m$^3$
   • (C)
     0.1 kg/m$^3$
   • (D)
     0.02 kg/m$^3$
10. 10.

    NEET 2020

    The average thermal energy for a mono-atomic gas is : ($k_B$ is Boltzmann constant and $T$, absolute temperature)

    • (A)
      $\frac12 k_BT$
    • (B)
      $\frac32 k_BT$
    • (C)
      $\frac52 k_BT$
    • (D)
      $\frac72 k_BT$