CBSE Class 9 Science Gas Laws MCQs Set A



1. Under which of the following conditions, Van der Waal's gas approaches ideal behaviour ? 
(A) Extremely low pressure
(B) High pressure
(C) Low product of PV
(D) Low temperature
2. A gas behaves like an ideal gas under conditions of 
(A) High pressure and low temperature 
(B) High temperature and high pressure 
(C) Low pressure and high temperature 
(D) Low pressure and low temperature 
3. When the temperature is raised, the viscosity of the liquid decreases.
This is because 
(A) Attraction between the molecules increases 
(B) Covalent and hydrogen bond forces decrease 
(C) Volume of the solution decreases 
(D) Increase in temperature increases the average kinetic energy of the molecules which over-comesthe attractive force between them 
4. Which of the following gases has the lowest average speed at 25°C ? 
(A) NH3
(B) O2
(C) CH4
(D) H2S
5. If the four tubes of a car are filled to the same pressure with N2, O2, H2 and Ne separately, then which one will be filled first ? 
(A) O2
(B) H2
(C) Ne
(D) N2

6. The correct equation for Boyle's law is :-

CBSE Class 9 Science gas Laws


7. An ideal gas expands according to PV = constant. On expansion,the temperature of gas
(A) will rise
(B) will drop
(C) will remain constant
(D) cannot be determined because the external pressure is not known
8. Some assumptions from the kinetic molecular theory are listed below. Which one is most frequently cited to explain Charle's law ?
(A) Collisions of gas particle are elastic and total kinetic energy of the gas is constant
(B) A gas consists of tiny particles moving in random straight line motion
(C) The volume of the particle is negligible compared to the volume of the gas
(D) The average kinetic energy of gas articles is proportional to the Kelvin temperature
9. Universal gas constant (R) is divided by Avogadro's number (N0) then the value is equivalent to
(A) van der Waal's constant (B) Rydberg's constant
(C) Planck's constant (D) Boltzmann's constant
10. The term that accounts for intermolecular force in van der Waal's equation for non ideal gas is
(A) RT (B) V – b (C) (P +α/V2) (D) (RT)–1
11. According to the kinetic energy of gases, in an ideal gas, between two successive collisions a gas molecules travels
(A) in a circular path (B) in a wavy path
(C) in a straight line path (D) with an accelerated velocity
12. The temperature at which real gases obey the ideal gas laws over a wide range of pressure is called
(A) Critical temperature (B) Boyle temperature
(C) Inversion temperature (D) Reduced temperature
13. A real gas at a very high pressure occupies
(A) Less volume then that of an ideal gas under identical condition
(B) More volume than that of an ideal gas under identical conditions
(C) Same volume than that of an ideal gas under identical conditions
(D) Cannot be predicted
14. Temperature according to kinetic theory, is a measure of
(A) Average translational kinetic energy of gas molecules
(B) Intermolecular attraction
(C) Intermolecular distances
(D) Volume f gas
15. A gas deviates from ideal behaviour at a high pressure because its molecules
(A) Show the Tyndall effect (B) Have kinetic energy
(C) Attract one another (D) Are bound by covalent bonds
16. Which statement about real gases is true ?
(A) Forces of attraction and repulsion exist between gas particles as close range
(B) The behaviour of real gases can be exactly predicted usig the ideal gas law
(C) The volume of the gas particle is zero
(D) The mass of the gas particles is zero
17. It is easter to liquefy oxygen than hydrogen because
(A) Oxygen has a higher critical temperature and a higher inversion temperature than hydrogen
(B) The critical temperature and inversion temperature of oxygen is very low
(C) Oxygen has a higher critical temperature and lower inversion temperature than hydrogen
(D) Oxygen has a lower critical temperature and higher inversion temperature than hydrogen

CBSE Class 9 Science gas Laws-ans



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