Practice Questions on Kinetic Theory of Gases with Answers.

**Questions on Kinetic Theory of Gases with Answers**

**Q1. What is the root-mean-square speed of a molecule of hydrogen gas at room temperature?**

(a) 1.93 m/s

(b) 19.3 km/s

(c) 19.3 m/s

(d) 1.93 km/s

**Q2. Consider oxygen gas at 30OK having the mass of its molecule as 5.31 x 10 ^{-20} kg. The root mean square speed of its molecules, is about**

(a) 284 m/s

(b) 248 m/s

(c) 348 m/s

(d) 484 m/s

**Q3. Assuming that the hydrogen molecules have a root-mean-square speed of 1,270 m/s at 300 K, calculate the rms at 600 K**

(a) 179.6 m/s

(b) 1796 m/s

(c) 2796 m/s

(d) 279.6 m/s

**Q4. The temperature of an ideal gas is increased from 120 K to 480 K. If at 120 K, the root mean square velocity of the gas molecules is v, at 480 K it becomes**

(a) 4v

(b) 2v

(c) v/2

(d) v/4

**Q5. Uranium has two isotopes of masses 235 and 238 units. If both are present in Uranium hexafluoride gas, what is the ratio of their rms speed?**

(a) 1.0010

(b) 0.0088

(c) 2.0044

(d) 1.0044

**Q6. Maintaining constant temperature, if the pressure of a given ideal gas is doubled, the r.m.s. speed of its molecule will**

(a) become zero

(b) Remain unchanged

(c) decrease

(d) increase

**Q7. The r.m.s. speed of nitrogen at STP , if the density of nitrogen is 1.251 Kg-m ^{3} at these conditions is**

(a) 490 km/s

(b) 490 mm/s

(c) 490 m/s

(d) 490 cm/s

**Q8. If a container contains a mixture of two ideal gases (of different molecular masses) at thermal equlibrium, which of the following is true?**

(a) The average kinetic energy of the lighter gas molecules is less than average kinetic energy of heavier gas molecules

(b) The average potential energy of the lighter gas molecule is greater than average potential energy of molecules of heavier gas

(c) The average speed of the molecules of the lighter gas is equal to the average speed of molecules of heavier gas

(d) The average speed of the molecules of the lighter gas is greater than the average speed of molecules of heavier gas

**Q9. A tiny particle of mass 1.4 × 10 ^{-11} kg is floating in air at 300K. Ignoring gravity, its r.m.s. speed (in um/s) due to random collisions with air molecules will be closest to**

(a) 0.3

(b) 3

(c) 30

(d) 300

**Q10. Estimate the temperature at which the root-mean-square velocity of nitrogen molecule in earth’s atmosphere equals the escape velocity from earth’s gravitational field. Take the mass of nitrogen molecule =28 amu and radius of earth = 6,400 km.**

(a) 1.4 × 10^{6} K

(b) 1.4 × 10^{7} K

(c) 1.4 × 10^{5} K

(d) 1.4 × 10^{4} K

**Q11. One mole of a gas is contained in a cube of side 0.2 m. If these molecules, each of mass 5 × 10 ^{-26} kg, move with the translational speed 483 m/s, calculate the pressure exerted by the gas on the sides of the cube.**

(a) 2.9 × 10^{5} N/m^{2}

(b) 2.9 × 10^{6} N/m^{2}

(c) 5.8 × 10^{5} N/m^{2}

(d) 5.8 × 10^{6} N/m^{2}

**Q12. A beam of hydrogen molecule H _{2}) is directed towards a wall, at an angle 60° with the normal to the wall Each molecule in the beam has a speed of 1.0 km/s and a mass of 3.3 × 10^{-27} kg. The beam strikes the wall over an area of 2.0 cm^{2}, at the rate of 10^{23} molecules per second. What is the beam’s pressure on the wall**

(a) 1.65 Pa

(b) 1.65 kPa

(c) 0.82 kPa

(d) 8.25 kPa

**Q13. The average translational kinetic energy of air molecules is 0.040 eV. The temperature of the air is (approximately) is**

(a) 83.7 K

(b) 31.0 K

(c) 837 K

(d) 310 K

**Q14. The average translational kinetic energy of O _{2} (molar mass 32) molecules at a particular temperature is 0.048 eV. The translational kinetic energy of N_{2} (molar mass 28) molecules in eV at the same temperature is**

(a) 0.0015

(b) 0.003

(c) 0.048

(d) 0.768

**Q15. The average kinetic energy of oxygen gas molecules at room temperature is 0.039 eV. The average kinetic energy of nitrogen gas molecules at room temperature is likely to be**

(a) 0.039 eV

(6) 0.078 eV

(c) 0.136 eV

(d) zero

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*Answer Key **(if you find any answer wrong, feel free to Correct us)*

*Answer Key*

01. | (d) | 06. | (b) | 11. | (a) |

02. | (d) | 07. | (c) | 12. | (a) |

03. | (b) | 08. | (d) | 13. | (d) |

04. | (b) | 09. | (c) | 14. | (c) |

05. | (d) | 10. | (d) | 15. | (a) |