NCERT Class 11 Chemistry Chapter 5 States Of Matter Gases And Liquids Very Short Question And Answers

NCERT Solutions For Class 11 Chemistry Chapter 5 States Of Matter Gases And Liquids Very Short Question And Answers

Question 1 Arrange O₂, CO₂, Ar, and SO₂ gases to present a sample of air in order of their increasing pressures.
Answer:

⇒ \(d_1=\frac{P M}{R T}, d_2=\frac{P M}{4 \times 8 R T}=\frac{1}{32} \frac{P M}{R T}=\frac{d_1}{32}\)

Question 2. Why is it not possible to liquefy an ideal gas?
Answer: Because of the absence of intermolecular forces of attraction in an ideal gas, such a gas cannot be liquefied

Question 3. Why is the nib of the fountain pen split?
Answer: The split part of the nib of a fountain pen acts like a capillary tube. The ink moves towards the tip of the die nib by capillary action against gravitation through the split par.

Read and Learn More NCERT Class 11 Chemistry Very Short Answer Questions

Question 4. At a constant temperature, gas A (volume VA and pressure PA) is mixed with gas B (volume VR and pressure PB). What will the total pressure ofthe gas mixture be?
Answer:

Total pressure ofthe gas mixture \(P=\frac{P_A V_A+P_B V_B}{V_A+V_B}\)

Question 5. For which of the following gas mixtures is Dalton’s law of partial pressures applicable? NO + O₂, CO₂ + CO , CO + O_2, CH₄ + C₂H₆,CO + H₂
Answer: Dalton’s law is applicable in case NO reacts with O₂ to form NO₂. CO reacts with O₂ to form CO₂. Hence, Dalton’s law does not apply to 1 and 3.

Question 6. In a mixture of A, B, and C gases, the mole fractions of A are 0.25 and 0.45, respectively. If the total pressure of the mixture is P, then find the partial pressure of B in the mixture.
Answer:

In the gas mixture, the mole of B =1- (0.25 + 0.45) = 0.3.

∴ The partial pressure of B in the mixture = 0.3 p.

Question 7. Why are diffusion rates of N₂O and CO₂ gases the same under identt of conditions?
Answer: N₂O and CO₂ have the same molar mass. So, diffusion rates will be equal at a certain temperature and pressure.

Question 8. At constant temperature and pressure, the rate of diffusion of H₂ gas is A/15 times. Find the value of n.
Answer:

⇒ \(\frac{r_{\mathrm{H}_2}}{r_{\mathrm{C}_n \mathrm{H}_{4 n-2}}}=\sqrt{\frac{16 n-2}{2}}=\sqrt{8 n-1}=\sqrt{15}\)

Question 9. Besides the lower layer, CO₂ is also found in the upper layer of the atmosphere, although it is heavier than O₂ or N₂—Explain.
Answer: The rate of diffusion of a gas is not influenced by the gravitational force. Hence, CO₂ diffuses throughout the atmosphere instead of residing only at the lower layer of the atmosphere.

Question 10. The molecular masses of A, B, and C are 2, 4, and 28, respectively. Arrange them according to their increasing rates of diffusion.
Answer:

Molar masses of the three gases follow the order: MA < MB < Mc So, at a certain temperature and pressure, diffusion rates will be in the order: rC<rB<rA.

QuestionWhichwhich type of gas molecules are the energy and translational kinetic energy equal?
Answer: For monatomic gases (He, Ne, etc.) the total kinetic energy and translational kinetic energy are equal.

Question 12. Which type of velocity does a gas molecule with average kinetic energy possess?
Answer: The average kinetic energy of a gas molecule \(=\frac{1}{2} m c_{r m s}^2.\). So, a gas molecule with average kinetic energy has the root-mean-square velocity.

Question 13. On what factors does the total kinetic energy of the molecules in a gas depend?
Answer: The total kinetic energy of the molecules in a gas depends on the absolute temperature as well as the amount of the gas.

Question 14. Between H₂ and CO₂ gas, which one has the value of compressibility factor greater than 1 at ordinary temperature and pressure?
Answer: At ordinary temperature and pressure, the compressibility factor of H₂ is greater than 1.

Question 15. Which types of intermodular forces of attraction act between the modules in liquid HF?
Answer: HF is a polar covalent molecule. Hence, the forces of attraction between HF molecules in their liquid state are dipole-dipole attraction and H -H-H-bonding.

Question 16. What do you mean by the pressure of the gas?
Answer: Since E₂>E₁, T₂>T₁. This is because, with the increase in the absolute temperature of a gas, the average kinetic energy of the gas molecules increases

Question 17. Mention the variables and constant quantities in Charles’ law
Answer: Variables; Volume ( V) and absolute temperature (T) and Constants: Mass (m) and pressure (P) of the gas.

Question 18. What is the numerical value of N/n?[N and n are the number of gas molecules and number of moles of gas]
Answer: Number of gas molecules (N) = several moles of the gas (n) x Avogadro’s number or\(\frac{N}{n}\) = Avogadro’s number = 6.022 x1023.

Question 19. The equation of state of a real gas is P(V-b) = RT. Can this gas be liquefied?
Answer: For the given gas, the value of van der Waals constant a = 0, indicates the absence of intermolecular forces of attraction in the gas. So this gas cannot be liquefied.

Question 20. At 25°C, the vapour pressure of ethanol is 63 torrs. What does it mean?
Answer: At 25°C, the pressure exerted by eth vapour vapour in equilibrium with the liquid ethanol is 63 torrs.

Question 21. Why is the equilibrium established in the evaporation of a liquid in a closed vessel at a constant temperature called dynamic equilibrium?
Answer: This is so called because the process of evaporation and condensation does not stop at equilibrium and they keep on occurring equally and take

Question 22. Which one between water and ethanol has greater surface tension at a particular temperature?
Answer: As intermolecular forces of attraction are stronger in water than in ethanol, the surface tension of water is greater than that of ethanol.

Question 23. Plot density vs pressure for a fixed mass of an ideal gas at a constant temperature.
Answer: Since docs for a given mass of gas at a constant temperature.

Question 24. What are the molar volumes of nitrogen and argon gases at 273.15K temperature and 1 atm pressure? [consider both the gases behave ideally]
Answer: At 273.15K and late pressure, both nitrogen and argon behave ideally. Hence, at this temperature and pressure, the molar volume of each of them will be 22.4L

Question 25. What is the value of the surface tension of a liquid at its critical temperature?
Answer: The surface tension of a liquid at critical temperature is zero because the surface of separation between the liquid and vapour disappears at this temperature.

Question 26. Among the following properties of a liquid, which one increases with the increase in temperature? Surface tension, viscosity and vapour pressure
Answer: Vapour pressure increases with an increase in temperature

Question 27. At a given temperature, the viscosity of liquid A is greater than that of liquid B. Which of these two liquids has stronger intermolecular forces of attraction?
Answer: The stronger the intermolecular forces of attraction of a liquid, the higher the viscosity will be. Therefore, the inter¬ molecular forces of attraction of A will be greater than B

Question 28. How does the average velocity or the root mean square velocity of gas molecules depend on temperature and pressure?
Answer: The average kinetic energy (c) and the root mean square velocity (c₂) of gas molecules are given by \(\bar{c}=\sqrt{\frac{8 R T}{M}}\) and \(c_{r m s}=\sqrt{\frac{3 R T}{M}}\)

Question 29. Why does oil spread over water when it is poured over water
Answer: The surface tension of water is greater than that of oil. Also, the density of oil is less than that of water. When oil is poured over water, the higher surface tension of water causes oil to spread over water.

Question 30. The vapour pressures of benzene and water at 50°C are 271 and 92.5 torr, respectively. Which one would you expect to have stronger intermolecular forces of attraction?
Answer: A liquid with strong intermolecular forces of attraction has low vapour pressure. Thus, intermolecular forces of attraction are stronger in water.

Question 31. Give two examples where capillary action occurs.
Answer: Due to capillary action, water from the soil reaches the leaves of a tree through its sWaterwater comes out through the pores of a clay pot and evaporates. As a result, the water in the pot gets cooled.

Question 32. Comment on the validity of Boyle’s law for the following reaction: N₃O₄(g) 2NO₂(g)
Answer: The number of molecules of N₂O₄ and NO₂ varies with the pressure at constant temperature. Hence, the mass ofthe gas mixture does not remain constant. Thus, Boyle’s law is not applicable here.

Question 33. The normal boiling point of diethyl ether is 34.6°C What will be its vapour pressure at this temperature?
Answer: At the normal boiling point of a liquid, the vapour pressure of the liquid is equal to the atmospheric pressure. Therefore, the vapour pressure of diethyl ether is at 34. Temperatureature is 1 atm or 760 torr.

Question 34. The normal boiling points of ethanol and benzene are 78.3°C and 80°C, respectively. Is the vapour pressure of ethanol lower than, greater than or equal to the vapour pressure of benzene?
Answer:

At the normal boiling point of a liquid, the vapour pressure of the liquid is equal to the atmospheric pressure. Therefore, the vapour pressure of ethanol at 78.3°C and that of benzene at 80°C are the same and equal to 1 atm.

Question 35. The normal boiling points of two gases A and B are -150°C and -18°C, respectively. Which one of the two gases will behave more like an ideal gas at STP?
Answer: The very low boiling point of A implies the very weak intermolecular forces of attraction in gas A. Hence, gas A will show more ideal behaviour at STP.

NCERT Solutions For Class 11 Chemistry Chapter 5 States Of Matter Gases And Liquids Fill In The Blanks

Question 1. 0.1 atm = _________________  Pa =___________________
Answer:

1. 1.013 × 10⁴

2. 76

Question 2. The plot of pressure (P) versus temperature (T) for an  ideal gas will be a straight line passing through the origin _____________  and ______________________ remain constant
Answer: Mass and volume

Question 3. At a given temperature and pressure, the density of CO₂ gas is greater than N2 gas, because  it the ___________________ greater than CO₂
Answer:  Molecular mass

Question 4. The density of CO₂ at ___________________  standard atmospheric pressure is 1.788 g-L^-1
Answer: 27°C

Question 5. The velocity of the gas molecules having average kinetic  energy is called  ___________________ 
Answer: Root mean square velocity

Question 6. At a particular temperature, the average kinetic energies of the S02 molecule and H2 molecule are___________________ 
Answer: Equal

Question 7. The most probable velocity of He atoms at 127°C is_____________
Answer: 40.78 m.s^-1

Question 8. The volume of 1 mole of a gas at STP is smaller than 22.4 L. The compressibility factor of that gas at STP is
___________________  one.
Answer: Less than

Question 9. In van der Waals equation__ _________________ effective size ofthe gas molecules.
Answer: ‘b’

Question 10. At low pressure and a particular temperature, the pressure of 1 mol of an ideal gas is ___________________  a real gas.
Answer: Greater than

Question 11. Due to the ___________________  becomes spherical.
Answer: Surface tension

Question 12. The aqueous solution of soaps can spread like a thin film because ___________________  the surface water tension of the aqueous solution of soap is
Answer: Less

Question 13. At a particular temperature, the viscosity coefficient of ethyl alcohol is  ___________________ than dimethyl ether
Answer: Greater.