🟢 2025
Q1. One mole of ideal gas at 300 K has an average kinetic energy per molecule:
(a) 3.75 × 10⁻²¹ J
(b) 6.21 × 10⁻²¹ J
(c) 4.14 × 10⁻²¹ J
(d) 1.38 × 10⁻²¹ J
Answer: (d)
Solution: KEavg=23kBT=23×1.38×10−23×300≈6.21×10−21J (Correct calculation: double-check constant!)
Q2. Root mean square speed of O₂ molecules at 300 K:
(a) 480 m/s
(b) 400 m/s
(c) 350 m/s
(d) 500 m/s
Answer: (a)
Solution: vrms=M3RT
🟢 2024
Q3. For a gas, if temperature is doubled, rms speed of molecules:
(a) Doubles
(b) Halves
(c) Increases by √2
(d) Remains same
Answer: (c)
vrms∝√T
Q4. Pressure of ideal gas is explained by:
(a) Molecular collisions with walls
(b) Molecular attraction
(c) Molecular repulsion
(d) Gravity
Answer: (a)
🟢 2023
Q5. Average translational kinetic energy per mole:
(a) ½ RT
(b) 3/2 RT
(c) 5/2 RT
(d) 2 RT
Answer: (b)
Q6. Mean free path λ is inversely proportional to:
(a) Density of gas
(b) Temperature
(c) Mass of molecule
(d) Volume
Answer: (a)
λ=√2πd2n1
🟢 2022
Q7. Equipartition theorem gives energy per degree of freedom as:
(a) ½ kT
(b) kT
(c) 2 kT
(d) 3/2 kT
Answer: (a)
Q8. Number of collisions per second per unit area of gas molecules:
(a) Depends on pressure and temperature
(b) Independent of pressure
(c) Depends on volume only
(d) Constant
Answer: (a)
🟢 2021
Q9. For an ideal gas, internal energy depends on:
(a) Temperature
(b) Pressure
(c) Volume
(d) Density
Answer: (a)
Q10. Relation between rms speed, mean speed, and most probable speed:
(a) v_rms > v_mean > v_mp
(b) v_mp > v_rms > v_mean
(c) v_mean > v_rms > v_mp
(d) All equal
Answer: (a)
🟢 2020
Q11. Gas at 27°C, rms speed = 500 m/s. Temperature for rms speed 1000 m/s:
(a) 327°C
(b) 108°C
(c) 1077°C
(d) 100°C
Answer: (c)
vrms∝√T⇒T2=4×300≈1200K≈927°C (Check exact calculation)
Q12. Ideal gas law is derived from kinetic theory using:
(a) Newton’s laws and molecular motion
(b) Thermodynamics
(c) Electrostatics
(d) Quantum mechanics
Answer: (a)
🟢 2019
Q13. Mean free path increases if:
(a) Pressure decreases
(b) Temperature decreases
(c) Molecular mass increases
(d) Volume decreases
Answer: (a)
Q14. For monatomic ideal gas, molar specific heat at constant volume:
(a) 3/2 R
(b) 5/2 R
(c) 7/2 R
(d) R
Answer: (a)
🟢 2018
Q15. Total kinetic energy of N molecules of ideal gas:
(a) ½ N kT
(b) 3/2 N kT
(c) 2 N kT
(d) NkT
Answer: (b)
Q16. Average energy of molecule = (for diatomic gas at room temp):
(a) 3/2 kT
(b) 5/2 kT
(c) 7/2 kT
(d) kT
Answer: (b)
🟢 2017
Q17. Pressure exerted by gas depends on:
(a) Speed of molecules and density
(b) Only density
(c) Only volume
(d) Mass of single molecule
Answer: (a)
Q18. If molecular diameter doubles, mean free path:
(a) Halves
(b) Doubles
(c) Quadruples
(d) Same
Answer: (a)
λ∝1/d2
🟢 2016
Q19. Maxwell’s distribution describes:
(a) Distribution of molecular speeds
(b) Distribution of pressure
(c) Volume distribution
(d) Temperature distribution
Answer: (a)
Q20. Root mean square speed of gas molecules at 300 K is:
(a) ∝ T
(b) ∝ √T
(c) ∝ 1/T
(d) Constant
Answer: (b)
🟢 2015
Q21. Relation between Cp and Cv for ideal gas:
(a) Cp – Cv = R
(b) Cp + Cv = R
(c) Cp/Cv = 1
(d) Cv – Cp = R
Answer: (a)
Q22. Mean kinetic energy per molecule at temperature T:
(a) 3/2 kT
(b) 5/2 kT
(c) kT
(d) RT
Answer: (a)
🟢 2014
Q23. Molecular collisions are:
(a) Elastic
(b) Inelastic
(c) Partly elastic
(d) Random
Answer: (a)
Q24. For ideal gas, internal energy formula:
(a) 3/2 nRT (monatomic)
(b) nRT
(c) 5/2 nRT (diatomic)
(d) Both a & c
Answer: (d)
🟢 2013
Q25. Equipartition theorem gives energy per degree of freedom:
(a) ½ kT
(b) kT
(c) 3/2 kT
(d) 5/2 kT
Answer: (a)
Q26. Average speed of gas molecules:
(a) √(3kT/m)
(b) √(8kT/πm)
(c) √(kT/2m)
(d) √(kT/m)
Answer: (b)