Answer:
1. Answer : (c) 0.4 atm
Explanation: Vapour pressure will be the same because it doesn't depend on the volume it depends only on Temperature.
2. Answer : (c) Gas
Explanation: Of the three states of matter, the gaseous state is the simplest and shows greatest uniformity in behaviour. Gases show almost similar behaviour irrespective of their chemical nature. This state is characterized by gases maintain neither the volume nor the shape. They completely fill the container in which they are placed.
3. Answer : (a) Attract one another
Explanation: At high pressure, the volume is decreased appreciably, so the attractive forces become large and the molecules are crowded together. Thus, pressure correction is necessary and the gas deviates more from ideal behaviour.
4. Answer : (d) Units of Volume, Temperature and Pressure
Explanation: The value of the universal gas constant R depends on the units used for pressure, volume and temperature. Therefore, it depends on the units of measurement.
5. Answer : (c) Volume occupied by the molecules
Explanation: In van der Waals equation of state, the constants a and b represent the magnitude of intermolecular attraction and excluded volume respectively and are specific to a particular gas. The constant b is a measure of the volume occupied by the molecules.
6. Answer : (b) Liquid
Explanation: The particles of a solid are closely packed in position and can only vibrate in place. The particles of a liquid and gas are free to move. A liquid has a definite volume but no definite shape, whereas a gas has neither a definite volume nor a definite shape.
7. Answer : (b) Capillary Action
Explanation: Capillarity, rise or depression of a liquid in a small passage such as a tube of small cross-sectional area, like the spaces between the fibres of a towel or the openings in a porous material. Capillarity is not limited to the vertical direction. Water is drawn into the fibres of a towel, no matter how the towel is oriented.
8. Answer : (b) Surface Tension
Explanation: The cohesive forces between liquid molecules is responsible for the surface tension. The molecules of water on the surface don't have like molecules around it.So the water droplets tend to be pulled into shape of spherical due to cohesive forces.Thats why, the drop of water is always spherical.
9. Answer : (b) Grahams Law
Explanation: Graham's law states that the rate of diffusion or of effusion of a gas is inversely proportional to the square root of its molecular weight. In the same conditions of temperature and pressure, the molar mass is proportional to the mass density.
10. Answer : (a) Boyles law
Explanation: P is inversely proportional to V when T and n are constant according to Boyle's law.
\(P\propto\frac{1}{V}\)
\(P=\frac{K_1}{V}\)
where K1 is proportionality constant.
11. Answer : (a) The particles move faster
Explanation: There is a great deal of empty space between particles, which have a lot of kinetic energy. The particles move very fast and collide into one another when the gas is heated up, causing them to diffuse, or spread out, until they are evenly distributed throughout the volume of the container.
12. Answer : (a) Ion - dipole forces
Explanation: The term van der Waals force is a general term for those intermolecular forces that include all forces except ion-dipole forces when are relatively strong. Ion-dipole forces occur between an ion(either a cation or an anion) and a polar molecule. The Dutch physicist J van der Waals was the first to suggest the importance of intermolecular forces.
13. Answer : (a) polarisability of interacting particles
Explanation: Greater the polarisability of the interacting particles, greater is the magnitude of interaction energy.
14. Answer : (a) HCl and He atoms
Explanation: HCl is a polar molecule, whereas He atoms are non-polar so in between them dipole-induced dipole interactions exist.
15. Answer : (a) He
Explanation: Intermolecular forces in He are van der Waals forces which are the weakest in nature.
16. Answer : (a) Solid < Liquid < Gas
Explanation: Gas molecules are in continuous random motion and have the highest energy. When the thermal energy of the gas molecules is decreased by reducing the temperature, the molecules come closer together and are converted into a liquid and further, when the thermal energy of the liquids is decreased, it is converted into solid state.
17. Answer : (a) Gases like liquids possess definite volumes
Explanation: Gases do not have definite shape and volume. Their volume is equal to the volume of the container.
18. Answer : (a) Moist air
Explanation: Dry air consists mostly of nitrogen and oxygen molecules, which weigh more than water molecules.Therefore, moist air is lighter than dry air if both are at the same temperature and pressure.
19. Answer : (a) Boiling point increases with increasing pressure
Explanation: The beans are cooked earlier in pressure cooker because boiling point decreases with increasing pressure.
20. Answer : (a) >1
Explanation: ∵ for H2 and He, PV > nRT and Z >1
21. Answer : (c) Isothermal process
Explanation: Boyle's law is applicable to an isothermal process where temperature remains constant.
22. Answer : (a) decreases
Explanation: On increasing pressure, the volume decreases and density increases. So, molecules get closer to each other hence mean free path also decreases.
23. Answer : (a) Boyle's law
Explanation: p1/d1 = p2/d2 (at a constant temperature) This is the Boyles law. So the case-Air at sea level is dense is studied under Boyles law.
24. Answer : (c) SO2
Explanation: The van der Waals constant a shows the force of attraction between two molecules. Hence, the higher the value of a, the higher the attraction. Therefore, the gas will be readily liquefied. Therefore, SO2 will be readily liquified.
25. Answer :(d) 280 ml
Explanation: \(\frac{V_1}{T_1}=\frac{V_2}{T_2}\)
\(\frac{300\;mL}{300\;K}=\frac{V_2}{280\;K}\)
V2 = 280mL
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