NCERT Solutions For Class 11 Chemistry Chapter 5 States Of Matter Gases And Liquids MCQ’s

NCERT Solutions For Class 11 Chemistry Chapter 5 States Of Matter Gases And Liquids Multiple Choice Questions

Question 1. Equal weight of CH₄ and H₂ are mixed in an empty container at 25°C. The fraction of the total pressure exerted by H₂ is

1. \(\frac{1}{9}\)
2. \(\frac{1}{2}\)
3. \(\frac{8}{9}\)
4. \(\frac{16}{17}\)

Answer: 3. \(\frac{8}{9}\)

The gas mixture contains equal masses of CH and H₂. Suppose, the mass of each of these gases = u>g so, in the mixture

⇒ \(x_{\mathrm{H}_2}=\frac{w / 2}{\frac{w}{2}+\frac{w}{16}}=\frac{8}{9} \text { and } x_{\mathrm{CH}_4}=1-x_{\mathrm{H}_2}=1-\frac{8}{9}=\frac{1}{9}\)

∴ The partial pressure of \(\mathrm{H}_2, p_{\mathrm{H}_2}=x_{\mathrm{H}_2} \times P=\frac{8}{9} P\) [p= total pressure of the mixture]

∴ \(\frac{p_{\mathrm{H}_2}}{P}=\frac{8}{9}\)

Question 2. Avan der Waals gas may behave ideally when

1. Volume is very low
2. Temperature is very high
3. The pressure is very
4. The temperature, pressure, and volume all are very high

Answer: 3. The pressure is very

A van der Waals gas behaves ideally when its temperature is very high or pressure is very low. At either of these two conditions, the volume of the gas becomes very large, which results in a large separation of gas molecules.

Thus, intermolecular forces of attraction become negligible, and gas behaves approximately like an ideal gas.

Question 3. Two gases X (mol. wt. Mx) and Y (mol. wt. My; My> Mx) are at the same temperature, in two different containers. Their root mean square velocities are Cx and CY respectively. If average kinetic energies per molecule of two gases X and Y are Ex and Ey respectively, then which of the following relation(s) is (are) true

1. Ex>EY
2. CX>CY
3. \(E_X=E_Y=\frac{3}{2} R T\)
4. \(E_X=E_Y=\frac{3}{2} k_B T\)

Answer: 3. \(E_X=E_Y=\frac{3}{2} R T\)

For 1 mol of a gas, van der Waals equation: \(\left(P+\frac{a}{V^2}\right)(v-b)=R T\) If the value of is negligible, then \(P+\frac{a}{V^2} \approx P\)

∴ P(V-b) = RT or, PV = RT + Pb \(\text { or, } \frac{P V}{R T}=1+\frac{P b}{R T} \quad \text { or, } Z=1+\frac{P b}{R T}\)

Question 4. The compressibility factor (Z) of one mole of a van der Waals gas of negligible ‘a’ value is-

1. 1
2. \(\frac{b P}{R T}\)
3. \(1+\frac{b P}{R T}\)
4. \(1-\frac{b P}{R T}\)

Answer: 3. \(1+\frac{b P}{R T}\)

For 1 mol of a gas, van der Waals equation: \(\left(p+\frac{a}{V^2}\right)(v-b)=R T\)

If the value of ‘a’ is negligible, the \(P+\frac{a}{V^2} \approx P\)

∴ P(V-b) = RT

⇒ \(\text { or, } P V=R T+P b \quad \text { or, } \frac{P V}{R T}=1+\frac{P b}{R T} \quad \text { or, } Z=1+\frac{P b}{R T}\)

Question 5. For one mole of an ideal gas, the slope of the V vs. T curve at a constant pressure of 2 atm is XL-moH-K¯¹. The value of the ideal universal gas constant ‘R’ in terms of X is

1. \(X \mathrm{~L} \cdot \mathrm{atm} \cdot \mathrm{mol}^{-1} \cdot \mathrm{K}^{-1}\)
2. \(\frac{X}{2} \mathrm{~L} \cdot \mathrm{atm} \cdot \mathrm{mol}^{-1} \cdot \mathrm{K}^{-1}\)
3. \(2 X \mathrm{~L} \cdot \mathrm{atm} \cdot \mathrm{mol}^{-1} \cdot \mathrm{K}^{-1}\)
4. \(2 X \mathrm{~atm} \cdot \mathrm{L}^{-1} \cdot \mathrm{mol}^{-1} \cdot \mathrm{K}^{-1}\)

Answer: 3. \(2 X \mathrm{~L} \cdot \mathrm{atm} \cdot \mathrm{mol}^{-1} \cdot \mathrm{K}^{-1}\)

⇒ \(P V=n R T \text { or, } P\left(\frac{V}{n}\right)=R T\)

or,PVm = RT [Vm = molar volume \(\text { or, } V_m=\frac{R}{P} T\)

At constant pressure, \(\frac{R}{P}\) = constant = K. So, at constant pressure, for 1 mol of an ideal gas, Vm = KT. This relation represents a straight-line equation passing through the origin. So, for 1 mol of an ideal gas at constant pressure, the graph of Vm vs. Twill be a straight line with slope = K.

Given,K= XL.mol¯¹.K¯¹.

⇒ \(\text { or, } \frac{R}{P}=X \mathrm{~L} \cdot \mathrm{mol}^{-1} \cdot \mathrm{K}^{-1} \quad \text { or, } \frac{R}{2 \mathrm{~atm}}=X \mathrm{~L} \cdot \mathrm{mol}^{-1} \cdot \mathrm{K}^{-1}\)

∴ R = 2XL-atm-mol-1.K-1

Question 6. At a certain temperature, the time required for the complete diffusion of 200 mL of H₂ gas is 30 minutes. The time required for the complete diffusion of 50 mL of O₂ gas at the same temperature will be

1. 60 mins.
2. 30 mins.
3. 45 mins.
4. 15 mins.

Answer: 2. 30 mins.

According to Graham’s law \(\frac{V_{\mathrm{H}_2} / t_1}{V_{\mathrm{O}_2} / t_2}=\sqrt{M_{\mathrm{O}_2} / M_{\mathrm{H}_2}}\)

⇒ \(\text { or, } \frac{V_{\mathrm{H}_2}}{V_{\mathrm{O}_2}} \times \frac{t_2}{t_1}=\sqrt{\frac{M_{\mathrm{O}_2}}{M_{\mathrm{H}_2}}} \text { or, } \frac{200}{50} \times \frac{t_2}{30 \mathrm{~min}}=\sqrt{\frac{32}{2}}=4\)

∴ T₂ = 30 min

Question 7. Four gases P, Q, R, and S have almost the same values but their ‘a! values (a, b are van der Waals constants) are in the order Q<R<S<P. At particular temperatures, among the four gases, the most easily liquefiable one is

1. P
2. Q
3. R
4. S

Answer: 1. P

The van der Waals constant ‘a’ of a gas is a measure of the intermolecular forces of attraction in the gas. The larger the value of ‘a’, the stronger the intermolecular forces of attraction. Now, a gas with strong intermolecular forces of attraction can easily be liquefied. So, the most easily liquefiable gas is P.

Question 8. Units of surface tension and viscosity are

1. \(\mathrm{kg} \cdot \mathrm{m}^{-1} \cdot \mathrm{s}^{-1}, \mathrm{~N} \cdot \mathrm{m}^{-1}\)
2. \(\mathrm{kg} \cdot \mathrm{s}^{-2}, \mathrm{~kg} \cdot \mathrm{m}^{-1} \cdot \mathrm{s}^{-1}\)
3. \(\mathrm{N} \cdot \mathrm{m}^{-1}, \mathrm{~kg} \cdot \mathrm{m}^{-1} \cdot \mathrm{s}^{-2}\)
4. \(\mathrm{kg} \cdot \mathrm{s}^{-1}, \mathrm{~kg} \cdot \mathrm{m}^{-2} \cdot \mathrm{s}^{-1}\)

Answer: 2. \(\mathrm{kg} \cdot \mathrm{s}^{-2}, \mathrm{~kg} \cdot \mathrm{m}^{-1} \cdot \mathrm{s}^{-1}\)

⇒ \(\text { Surface tension }=\frac{\text { Force }}{\text { Length }}=\frac{\mathrm{N}}{\mathrm{m}}=\frac{(\mathrm{kg} \cdot \mathrm{m} \cdot \mathrm{s})^{-2}}{\mathrm{~m}}=\mathrm{kg} \cdot \mathrm{s}^{-2} \text {. }\)

Coefficient of viscosity =  \(\mathrm{N} \cdot \mathrm{m}^{-2} \cdot \mathrm{s}=\mathrm{kg} \cdot \mathrm{m} \mathrm{s}^{-2} \cdot \mathrm{m}^{-2} \cdot \mathrm{s}\)

\(\mathrm{kg} \cdot \mathrm{m}^{-1} \cdot \mathrm{s}^{-1}\)

Question 9. A gas can be liquefied at temperature T and pressure P if-

1. T= TC, P<PC
2. T<TC,P>PC
3. T>TC,P>PC
4. T>TC,P<PC

Answer: 2. Two important conditions for liquefying a gas are— temperature should be lower than critical temperature (T<TC) and pressure should be greater than critical pressure (P > Pc).

Question 10. The rms velocity of CO₂ gas molecules at 27°C is approximately 1000 m/s. For N₂ molecules at 600K the rms velocity approximately

1. 2000 m/s
2. 1414 m/s
3. 1000 m/s
4. 1500 m/s

Answer: 3. 1000 m/s

⇒ \(c_{r m s}=\sqrt{\frac{3 R T}{M}} \text {, so, } \frac{c_{r m s}(\mathrm{CO})}{c_{rms}\left(\mathrm{~N}_2\right)}=\sqrt{\frac{3 R T_{300}}{M_{\mathrm{CO}}} \times \frac{M_{N_2}}{3 R T_{600}}}\)

Question 11. Among tire following which should have the highest rms speed at the same temperature

1. SO₂
2. CO₂
3. O₂
4. H₂

Answer: 4. H₂

⇒ \(c_{r m s}=\sqrt{\frac{3 R T}{M}} \quad \text { or, } c_{r m s} \propto \frac{1}{\sqrt{M}}\)

Question 12. Which of the following has the dimension of ML⁰T^-2 

1. Coefficient of viscosity
2. Surface tension
3. Vapour pressure
4. Kinetic energy

Answer: 2. Surface tension \(\gamma=\frac{\text { force }}{\text { length }}\)

⇒ \(\text { or, } \gamma=\frac{\text { mass } \times \text { acceleration }}{\text { length }}\)

⇒ \(=\frac{\mathrm{M} \times \mathrm{LT}^{-2}}{\mathrm{~L}}=\mathrm{ML}^0 \mathrm{~T}^{-2}\)

Question 13. For the same mass of two different ideal gases molecular weights M₁ and M₂, plots of logV vs logP at a given constant temperature are shown.

Identify the correct option-

1. M₁>M₂
2. M₁=M₂
3. M₁<M₂
4. Can be predicted only if the temperature is known

Answer: 1. M₁>M₂ From the ideal gas equation

P V = n R T = \(frac{W}{M} R T\)

Or,PV= \(\frac{k}{M}\)

Where k = WRT

Or, \(\log P+\log V=\log \frac{k}{M}\)

Or,  \(\log V=-\log P+\log \frac{\kappa}{M}(y=m x+c)\)

According to the intercepts in the graph

⇒ \(\log \frac{k}{M_2}>\log \frac{k}{M_1}\) \(\text { or, } \frac{k}{M_2}>\frac{k}{M_1} \quad \text { or, } M_1>M_2\)

Question 14. Equal weights of ethane and hydrogen are mixed in an empty container at 25°C. The fraction of total pressure exerted by hydrogen is

1. 1: 2
2. 1:1
3. 1:16
4. 15:16

Answer: 4. 15:16

Let, wc₂H₆ = wH₂ = w

⇒ \(n_{\mathrm{C}_2 \mathrm{H}_6}=\frac{w}{30} \text { and } n_{\mathrm{H}_2}=\frac{w}{2}\)

∴ \(n_{\mathrm{C}_2 \mathrm{H}_6}=\frac{w}{30} \text {. and } n_{\mathrm{H}_2}=\frac{w}{2}\)

∴ \(x_{\mathrm{C}_2 \mathrm{H}_6}=\frac{n_{\mathrm{C}_2 \mathrm{H}_6}}{n_{\mathrm{C}_2 \mathrm{H}_6}+n_{\mathrm{H}_2}}=\frac{\frac{1}{30}}{\frac{1}{30}+\frac{1}{2}}=\frac{1}{16}\)

[n= number of moles, x = mole fraction]

Similarly \(x_{\mathrm{H}_2}=\frac{15}{16}\)

According to Dalton’s law of partial pressure

⇒ \(p_{\mathrm{H}_2}=x_{\mathrm{H}_2} \times P \quad[P=\text { total pressure }] \)

⇒  \(\frac{P_{\mathrm{H}_2}}{P}=x_{\mathrm{H}_2}=\frac{15}{16}\)

Question 15. Compressibility factor for a real gas at high pressure

1. 1
2. \(1+\frac{P b}{R T}\)
3. \(1-\frac{P b}{R T}\)
4. \(1+\frac{R T}{P b}\)

Answer: 2. \(1+\frac{P b}{R T}\)

Van der Waals equation \(\left(P+\frac{a}{V^2}\right)(V-b)=R T\)

At high pressure \(P \gg \frac{a}{V^2}\) hence, P(V-b) = RT

⇒ \(\text { or, } P V=R T+P b \text { or, } \frac{P V}{R T}=1+\frac{P b}{R T} \text { or, } Z=1+\frac{P b}{R T}\)

Question 16. ‘a’ and ‘b’ are van der Waals constant for gases. Chlorine is more easily liquefied them ethane because

1. A and B for Cl₂ < A and B for C₂H₆
2. A for Cl₂ < A for C₂H₆ but B for Cl₂ > B for C₂H₆
3. A for Cl₂ > A for C₂H₆ but B for Cl₂< B for C₂H₆
4. A and B for Cl₂ > A and B for C₂H₆

Answer: 3. A for Cl₂ > A for C₂H₆ but B for Cl₂ < B for C₂H₆

Van der Waals constants ‘a’ is a measure of intermolecular forces of attraction of a gas whereas ‘b’ is a measure of the size of gas molecules. Hence, more is the value of a more easily the gas will be liquefied.

Question 17. For the gaseous state, if the most probable speed is denoted by c, average speed by c, and mean square speed by c, then for a large number of molecules the ratios of these speeds are

1. c*:c:c = 1.225: 1.128: 1
2. c*:c:c = 1.128: 1.225: 1
3. c*:c:c = 1:1.128:1.225
4. c*:c:c = 1:1.225:1.128

Answer: 4. c*:c:c = 1:1.225:1.128

Question 18. If Z is a compressibility factor, the van der Waals equation at low pressure can be written as

1. \(Z=1+\frac{P b}{R T}\)
2. \(Z=1+\frac{R T}{P b}\)
3. \(Z=1-\frac{a}{R T V}\)
4. \(Z=1-\frac{P b}{R T}\)

Answer: 3. \(Z=1-\frac{a}{R T V}\)

Van der Waals constant ‘a’ is a measure of intermolecular forces of attraction of a gas whereas ‘b’ is a measure of the size of gas molecules. Hence, more is the value of a more easily the gas will be liquefied.

Question 19. The ratio of masses of oxygen and nitrogen in a gaseous mixture is 1:4 ratio of the number of their molecule is

1. 3:16
2. 1:4
3. 7:32
4. 1:8

Answer: 4. 1:8

Question 20. Intermolecular interaction that is dependent on the inverse cube of the distance between the molecules

1. London force
2. Hydrogen bond
3. ion ion interaction
4. ion-dipole interaction

Answer: 1. London force

1, 3, and 4, are not applicable as the interaction is intermolecular. 2 is not the correct choice as the hydrogen bond does not follow the relation mentioned above.

Question 21. Two closed bulbs of equal volume ( V) containing an Ideal gas Initially at pressure pt and temperature T₁ are connected through a narrow tube of negligible volume. The temperature of one of the bulbs is then raised to 7 2. The final pressure p₁ Is-

1. \(p_1\left(\frac{T_1 T_2}{T_1+T_2}\right)\)
2. \(2 p_i\left(\frac{T_1}{T_1+T_2}\right)\)
3. \(2 p_1\left(\frac{T_2}{T_1+T_2}\right)\)
4. \(2 p_i\left(\frac{T_1 T_2}{T_1+T_2}\right)\)

Answer: 3. \(2 p_1\left(\frac{T_2}{T_1+T_2}\right)\)

n₁+n₂=n₁‘+n’₂

∴ \(\frac{p_i V}{R T_1}+\frac{p_i V}{R T_1}=\frac{p_f V}{R T_1}+\frac{p_f V}{R T_2}\)

Question 22. A gas mixture was prepared by taking equal moles of CO and N₂. If the total pressure of the mixture was 1 atm, the partial pressure of N₂ in the mixture is

1. 0.5 atm
2. 0.8 atm
3. 0.9 atm
4. 1 atm

Answer: 1. 0.5 atm

In the mixture \(x_{\mathrm{N}_2}=\frac{1}{2} \text { and } x_{\mathrm{CO}}=\frac{1}{2}\)

∴ \(p_{\mathrm{N}_2}=x_{\mathrm{N}_2} \times P=\frac{1}{2} \times 1 \mathrm{~atm}=0.5 \mathrm{~atm}\)

Question 23. Two gases A and B having the same volume diffuse through a porous partition in 20 and 10 seconds respectively. Molar mass ofA is 49u. The molecular mass will be—

1. 50.00u
2. 12.25u
3. 6.50u
4. 25.00u

Answer: 2. 12.25u

⇒ \(\frac{r_A}{r_B}=\sqrt{\frac{M_B}{M_A}} \text { or, } \frac{V / 20}{V / 10}=\sqrt{\frac{M_B}{49}} \text { or, } \frac{1}{2}=\sqrt{\frac{M_B}{49}}\)

∴ Mb = 12.25u

Question 24. By what factors does the average velocity of a gas molecule increase when the temperature (inK) is doubled

1. 2.0
2. 2.8
3. 4.0
4. 1.4

Answer: 4. 1.4

⇒ \(\bar{c}=\sqrt{\frac{8 R T}{\pi M}}\)

When Pis doubled, \(\bar{c}_1=\sqrt{\frac{8 R \times 2 T}{\pi M}}=\sqrt{2} \sqrt{\frac{8 R}{\pi M}}\)

∴ MB= 12.25u

Question 25. 50mL of each gas A and B takes 150s and 200s respectively for effusing through a pinhole under similar conditions. If the molar mass of gas B is 36, the molar mass of gas A—

1. 20.25
2. 64
3. 96
4. 128

Answer: 1. 20.25

⇒ \(\frac{r_A}{r_B}=\sqrt{\frac{M_B}{M_A}} \text { or, } \frac{V_A}{t_A} \times \frac{t_B}{V_B}=\sqrt{\frac{M_B}{M_A}}\)

⇒ \(\text { or, } \frac{50}{150} \times \frac{200}{50}=\sqrt{\frac{36}{M_A}} \text { or, } \frac{4}{3}=\sqrt{\frac{36}{M_A}} \text { or, } \frac{16}{9}=\frac{36}{M_A}\)

∴ \(M_A=\frac{36 \times 9}{16}=20.25\)

Question 26.

1. Set-1: O₂, CO₂, H₂ and He,
2. Set-2: CH₄, O₂ and H₂.

The gases in set-I in increasing order of ’b’ and gases given in set-II in decreasing order of ‘a’ are arranged below here ‘a’ and ‘b’ are van der Waals constants. Select the Correct order from the following

1. O₂ < He < H₂ < CO₂ ; H₂ >O₂ > CH₂
2. H₂ < He < O₂ < CO₂; CH₄ >O₂ > H₂
3. H₂ < O₂< He < CO₂ ; O₂ > CH₄ > H₂
4. He < H₂ < CO₂ < O₂ ; CH₄ > H₂ > O₂

Answer: 2. H₂ < He < O₂ < CO₂ ; CH₄ > O₂ > H₂

A gas with strong intermolecular forces of attraction has a large value of a and a gas has a large value of ‘b’ if its molecules are big. The increasing order of sizes of H₂, He, O₂, and CO₂ molecules is H₂ < He <O₂ < CO₂. So, the increasing order of values for these gases is H₂ < He < O₂ < CO₂. CH₄, O₂, and H₂ are all non-polar molecules.

The only intermolecular forces of attraction that act in CH₄, O_2, and H₂ gases are London forces. The strength of London forces increases with molecular size.

So, the increasing order of intermolecular forces in CH_4, O₂, and H₂ gases will be CH₄ > O₂ > H₂. Again, the stronger the intermolecular forces of attraction in a gas, the larger the value of the gas. Therefore, the decreasing order of ‘b’ values for these gases will be CH₄ > O₂ > H₂.

Question 27. A certain gas takes three times as long to effuse out ns helium. Its molecular mass will be

1. 36u
2. 64u
3. 9u
4. 27u

Answer: 1. 36u

⇒ \(\frac{r_1}{r_2}=\sqrt{\frac{M_2}{M_1}} \text { or, } \frac{v / t_1}{v / t_2}=\sqrt{\frac{M_2}{M_1}} \text { or, } \frac{t_2}{t_1}=\sqrt{\frac{M_2}{M_1}}\)

Or, \(\frac{3}{1}=\sqrt{\frac{M_2}{4 \mathrm{u}}} \text { or, } M_2=36 \mathrm{u}\)

[t₁ and t₂ are the times for the diffusion of VmLHe and VmL unknown gas respectively. M₁ = molar mass of He, M₂ = molar mass of unknown gas]

Question 28. Maximum deviation from Ideal gas is expected in case of—

1. CH₄(g)
2. NH₃(g)
3. H₂(g)
4. N₂(g)

Answer: 2.

NH₃(g) CH₄, H₂ and N₂ are non-polar molecules. Only intermolecular forces that operate in CH₄, H₂, and N₂ gases are weak London forces.

As NH₃ is a polar molecule, besides weak London forces, relatively stronger dipole-dipole attractive forces also act among the molecules in NH₃ gas. So, among the given gases, intermolecular forces of attraction will be strongest in NH₃, and hence it will show maximum deviation from ideal behaviour.

Question 29. Equal masses of H₂, O₂, and methane have been taken in a container of volume V at a temperature of 27°C in identical conditions. The ratio of the volumes of gases H₂: O₂: methane would be –

1. 8:16:1
2. 16:8:1
3. 16:1:2
4. 8:1:2

Answer: 3. 16:1:2

Let the mass of each of the gases be wg. In the mixture

⇒ \(n_{\mathrm{H}_2}=\frac{w}{2} \mathrm{~mol}, n_{\mathrm{O}_2}=\frac{w}{32} \mathrm{~mol} \text { and } n_{\mathrm{CH}_4}=\frac{w}{16} \mathrm{~mol} \text {. }\)

Total number of moles in the mixture \(=\frac{w}{2}+\frac{w}{32}+\frac{w}{16}=\frac{19}{32} w\)

So,in the mixture, \(x_{\mathrm{H}_2}=\frac{w / 2}{19 w / 32}=\frac{16}{19}, x_{\mathrm{O}_2}=\frac{1}{19}\) and \(x_{\mathrm{CH}_4}=\frac{2}{19} .\)

The volume fraction of a component in the mixture = mole fraction ofthe component x total volume ofthe mixture

∴ \(V_{\mathrm{H}_2}=\frac{16}{19} \times V, V_{\mathrm{O}_2}=\frac{1}{19} \times V \text { and } V_{\mathrm{CH}_4}=\frac{2}{19} \times V\)

∴ \(V_{\mathrm{H}_2}: V_{\mathrm{O}_2}: V_{\mathrm{CH}_4}=16: 1: 2\)

Question 30. A gas such as carbon monoxide would be most likely to obey the ideal gas law at

1. High temperatures and low pressures
2. Low temperatures and high pressures
3. High temperatures and high pressures
4. Low temperatures and low pressures

Answer: 1. High temperatures and low pressures

At high temperatures and low pressures, real gases show ideal behaviour

Question 31. Equal moles of hydrogen and oxygen gases are placed in a container with a pinhole through which both can escape. What fraction of the oxygen escapes in the time required for one-half of the hydrogen to escape

1. \(\frac{1}{2}\)
2. \(\frac{1}{8}\)
3. \(\frac{1}{4}\)
4. \(\frac{3}{8}\)

Answer: 2. \(\frac{1}{8}\)

⇒ \(\text { } \frac{r_{\mathrm{O}_2}}{r_{\mathrm{H}_2}}=\sqrt{\frac{M_{\mathrm{H}_2}}{M_{\mathrm{O}_2}}} \text { or, } \frac{n_{\mathrm{O}_2} / t}{0.5 / t} \quad \text { or, } n_{\mathrm{O}_2}=\frac{1}{8}\)

Question 32. The correction factor ‘a’ to the ideal gas equation corresponds to—

1. Forces of attraction between the gas molecules
2. Density of the gas molecules
3. The electric field present between the gas molecules
4. The volume of the gas molecules

Answer: 1. Forces of attraction between the gas molecules

In the real gas equation \(\left(P+\frac{a n^2}{V^2}\right)(V-n b)=n R T \text {; }\) van der Waals constant ‘ a ‘ represents the intermolecular forces attraction between the molecules.

Question 33. Given van der Waals constant of NH₃, H₂, O₂, and CO₂ are respectively 4.17, 0.244, 1.36, and 3.59. Which one of the following gases is most easily liquefied—

1. NH₃
2. H₂
3. O₂
4. CO₂

Answer: 1. NH₃ The gases having strong intermolecular attraction have a value of van der Waals constant Such gases can be liquefied easily. Among the given gases NH₃ has the highest value of a.

Question 34. In the van der Waals equation, ‘ a ‘ signifies

1. Intermolecular attraction
2. Intramolecular attraction
3. The attraction between molecules and walls of the container
4. Volume of molecules

Answer: 1. Intermolecular attraction

In van der Waals equation, a signifies the intermolecular forces of attraction

Question 35. Arrange the following gases in order of their critical temperature: NH₃, H₂, CO₂, O₂

1. NH₃ > H₂O > CO₂ > O₂
2. O₂>CO₂>H₂O>NH₃
3. H₂O > NH₃ > CO₂ > O₂
4. CO₂ >O₂ > H₂O > NH₃

Answer: 3. H₂O > NH₃ > CO₂> O₂

The greater the intermolecular forces of attraction, the higher the critical temperature

Question 36. The density of gas A is thrice that of a gas B at the same temperature. The molecular weight of gas B is twice that of A. What will be the ratio of the pressures acting on B and A —

1. \(\frac{1}{4}\)
2. \(\frac{7}{8}\)
3. \(\frac{2}{5}\)
4. \(\frac{1}{6}\)

Answer: 4. \(\frac{1}{6}\)

⇒ \(\frac{d}{p}=\frac{M}{R T}\)

⇒ \(\frac{1}{6}\)

Let density ofgas B be d

∴ The density of gas A = 3d and molecular weight of A be M.

∴ Molecular weight of B = 2M Since, R is gas constant and T is the same for gases, so

⇒ \( p_A=\frac{d_A R T}{M_A} \text { and } p_B=\frac{d_B R T}{M_B}\)

⇒ \(\frac{p_B}{p_A}=\frac{d_B}{d_A} \times \frac{M_A}{M_B}=\frac{d}{3 d} \times \frac{M}{2 M}=\frac{1}{6}\)

Question 37. In van der Waals equation at constant temperature 300k, if a = 1.4 atm-L²-mol^-2, V = 100 mL, n = 1 mole, then what is the pressure of the gas

1. 42 atm
2. 210 atm
3. 500 atm
4. 106 atm

Answer: 4. 106 atm

At moderate pressure, the van der Waals equation is given

⇒ \(\left(P+\frac{a n^2}{V^2}\right)(V)=n R T\)

⇒ \(\left(P+\frac{1.4}{(0.1)^2}\right)(0.1)=1 \times 0.082 \times 300\)

or, (P+ 140) ×  0.1 = 24.6 or, 0.1, P+ 14 = 24.6

or, 0.1 P = 10.6 or, P = 106 atm

Question 38. When 1 g of gas A at 4 bar pressure is added to 2 g of gas B, the total pressure inside the container becomes 6 bar. Which of the following is true

1. MA= 2MB
2. MB=2MA
3. MA=4MB
4. MB=4MA

Answer: 4. MB=4MA

⇒ \(\frac{n_1}{p_1}=\frac{n_2}{p_2}\)

∴ \(\frac{\frac{1}{M_A}}{4}=\frac{\frac{1}{M_A}+\frac{2}{M_B}}{6}\)

⇒ \(\text { or, } \frac{6}{4 M_A}-\frac{1}{M_A}=\frac{2}{M_B}\)

⇒ \(\text { or, } \frac{6-4}{4 M_A}=\frac{2}{M_B} \quad \text { or, } \frac{1}{4 M_A}=\frac{1}{M_B} \quad \text { or, } M_B=4 M_A\)

Question 39. Gas in a cylinder is maintained at 10 atm pressure and 300 K temperature. The cylinder will explode if the pressure of the gas goes beyond 15 atm. What is the maximum temperature to which gas can be heated

1. 400k
2. 500k
3. 450k
4. 250k

Answer: 3. 450k

⇒ \(\frac{P_1}{T_1}=\frac{P_2}{T_2}\)

∴ \(\frac{10}{300}=\frac{15}{T_2} \quad \text { or, } T_2=450 \mathrm{~K}\)

Question 40. Two separate bulbs contain gas A and gas B. The density of gas A is twice that of B. The molecular mass of A is half that of B. If temperature is constant, the ratio of the pressure of A and B is-

1. 1:1
2. 1:2
3. 4:1
4. 2:1

Answer: 3. 4:1

⇒ \(d=\frac{P M}{R T}\)

Given = \(\frac{d_A}{d_B}=2, \frac{M_A}{M_B}=\frac{1}{2} \)

= \(\frac{d_A}{d_B}=\frac{P_A M_A}{R T} \times \frac{R T}{P_B M_B}=2 \)

Or,  \(\frac{P_A}{P_B} \times \frac{M_A}{M_B}=2 \)

Or,  \( \frac{P_A}{P_B} \times \frac{1}{2}=2 \)

Or,  \(\frac{P_A}{P_B}\)

= 4: 1

Question 41. Which of the following does not change during compression of a gas at a constant temperature—

1. Density of a gas
2. Distance between molecules
3. The average speed of molecules
4. The number of collisions

Answer: 3. Average speed of molecules

Question 42. For which of the following gaseous mixtures, Dalton’s law of partial pressure is not applicable—

1. SO₂, HE, NE
2. NH₃, HBr, HC₁
3. O₂,N₂,CO₂
4. N₂,H₂,O₂

Answer: 2. NH₃, HBr, HCl

Question 43. The volume of a given mass of an ideal gas is VL at 27°C and 1 atm pressure. If the volume of the gas is reduced by 80% at constant pressure, the temperature of the gas will have to be—

1. -50°C
2. -127°C
3. -200°C
4. -213°C

Answer: 4. -213°C

Question 44. AT STP, the density of air is 1.3 × 10¯³g.cm¯³. The vapour density of air is—

1. 1.3
2. 14.6
3. 2.56
4. 10.8

Answer: 2. 14.6

Question 45. At a given temperature; the molar concentration of N₂ is greater than that of H₂ in a mixture of N₂ and H₂ gases present in a closed container. If the average kinetic energies of N₂ and H₂ molecules are xj and yj respectively, then

1. x>y
2. x<y
3. x = y
4. Impossible To Predict

Answer: 3. Impossible To Predict

Question 46. The density of gas A is dA at a temperature of TAK, and the density of gas B is dB at a temperature of TBK. The molar mass of A is 4 times that of B. If TA : TB = 2:1 and dA : dB = 1:2, the ratio of pressures of A to B is

1. 2:1
2. 1:8
3. 3:2
4. 1:4

Answer: 4. 1:4

Question 47. Two gases A and B have respective van der Waals constants a₂, bx and a₂, b₂. If ‘ A ’ is more compressible than ‘B,’ then which of the following conditions has to be satisfied

1. a₁ = a₂ and b₁> b₂
2. a₁ < a₂ and b₁> b₂
3. a₁ < a₂ and b₁ = b₂
4. a₁ > a₂and b₁ < b₂

Answer: 4. a₁ > a₂and b₁ < b₂

Question 48. The dimension of the coefficient of viscosity

1. MLT
2. ML^-1T^-1
3. MLT^-1
4. MLT^-2

Answer: 2. ML^-1T^-1

Question 49. The densities of water and water vapour are 1.0 g.cm¯³ and 0.0006 g.cm¯³ respectively at 100°C and 1 atm pressure. At this temperature, the total volume occupied by water molecules in 1L of water vapour is

1. 2.24 cc
2. 0.6 cc
3. 0.12 cc
4. 1.72 cc

Answer: 2. 0.6 cc

Question 50. The most probable velocities of the molecules of gas A (molar mass 16 g.mol¯¹) and that of the molecules of gas B (molar mass 28 g.mol¯¹) are the same. If the absolute temperatures of the gases A and B are T(A) and T{B) respectively, then

1. T{A) = 2T{B)
2. T(B) = 3T(A)
3. T(B) = 1.75 T (A)
4. T(B) = 2.5 T (A)

Answer: 3. T(B) = 1.75 T (A)

Question 51. At a given temperature and pressure, the volume of 1 mol of an ideal gas is 10L. At the same temperature and pressure, the volume of 1 mol of a real gas is VL. At this temperature and pressure, if the compressibility factor of the real gas is greater than 1, then

1. V- 10L
2. V< 10L
3. V> 10L
4. V< 10L

Answer: 3. V> 10L

Question 52. The pressure of a gas increases when its temperature is increased at constant volume. This is because with an increase in temperature—

1. The collision frequency of the gas molecules increases.
2. Motions of the gas molecules become more random
3. Gas molecules make more collisions with the walls of the container
4. The compressibility factor of the gas increases

Answer: 3. Gas molecules make more collisions with the walls of the container

Question 53. Under given conditions, the rate of diffusion of CH₄ gas is times that of f₂ gas. Gas 2 reacts with element A to form gaseous compounds AB₂ and AB₃. Under a given condition, the rate of diffusion of AB₂ is 1.12 times that of AB₃ The atomic mass of A (in g-mol^-1) is—

1. 32
2. 16
3. 8
4. 24

Answer: 1. 32

Question 54. Two flasks are connected by a valve: One of them with volume 5L contains 0.1 mol of H₂ at 27°C and the other with volume 2L contains 0.1 mol of N₂ at the same temperature. If the valve is opened keeping temperature constant, then at equilibrium the contribution of H₂ gas to the total pressure of the gas mixture

1. Is the same as that of n₂ gas
2. Is greater than that of n₂ gas
3. Is less than that of n₂ gas
4. Cannot be predicted

Answer: 1. Is the same as that of n₂ gas

Question 55. A balloon filled with acetylene is pricked by a pin and dropped readily in a tank of H₂ gas under identical conditions. After a while the balloon will—

1. Enlarge
2. Shrink completely
3. Collapse remain
4. Unchanged in size

Answer: 1. Enlarge

Question 56. At STP, the density of a gas is 1.25g-l^-1. The molar concentration (mol^-1) of 0.7g of this gas at 27°C and a pressure of 2 atm is

1. 0.27
2. 0.08
3. 0.19
4. 0.64

Answer: 2. 0.08

Question 57. 100 persons are sitting at equal distances in a row XY. Laughing gas (N₂O) is released from side X and tear gas (mol. mass = 176) from side Y at the same moment and the same pressure. The person who will tend to laugh and weep simultaneously is

1. 34th from side X
2. 67th from side X
3. 76th from side X
4. 67th from side Y

Answer: 2. 67th from side X

Question 58. van der Waals constant, b of a gas is 4.42 centilitre – mol 1. How near can the centres of 2 molecules approach each other

1. 127.2pm
2. 427.2pm
3. 327.2pm
4. 627.2pm

Answer: 3. 327.2pm

Question 59. Which of the following liquids has the least surface tension

1. Acetic acid
2. Diethyl ether
3. Chlorobenzene
4. Benzene

Answer: 2. Diethyl ether

Question 60. At P atm pressure and TK, a spherical air bubble is rising from the depth of a lake. When it comes to the surface of the lake the percentage increase in the radius will be (assume pressure and temperature at the surface to be PI₄ atm and 27TC respectively)—

1. 100%
2. 50%
3. 40%
4. 200%

Answer: 1. 100%

Question 61. A given mass of a perfect gas is first heated in a small and then in a large vessel, such that their volumes remain unaltered. The P- T curves are

1. Parabolic with the same curvature
2. Linear with the same slope
3. Linear with different slopes
4. Parabolic with different curvatures

Answer: 3. Linear with different slopes

Question 62. At a given temperature, most of the molecules in a sample of oxygen gas move with a velocity of 4.08× 10⁴ cm. s^-1. The average velocity of the molecules of the gas at the same temperature is—

1. 1.7 × 10⁴ cm.s¯¹
2. 4.6 × 10⁴ cm.s¯¹
3. 5.0 × 10⁴ cm.s¯¹
4. 8.9 × 10³ cm.s¯¹

Answer: 2. 4.6 × 10⁴ cm.s¯¹

Question 63. There is a depression in the surface of the liquid inside a capillary tube when—

1. The cohesive force is greater than
2. The adhesive force the adhesive force is greater than
3. The cohesive force both adhesive and cohesive forces are equal
4. None of the above is true

Answer: 1. The cohesive force is greater than

Question 64. One mol of a real gas following the equation, P(V-b) = RT, has a compressibility factor of 1.2 at 0°C and 200 atm pressure. The value of ‘b’ for this gas is—

1. 0.03521 L-mol¯¹
2. 0.0224 L-mol¯¹
3. 0.04610 L-mol¯¹
4. 0.01270 L-mol¯¹

Answer: 2. 0.0224 L-mol¯¹

Question 65. At a given temperature, the root mean square velocity of O₂ molecules is times that of the molecules of a gas. The molar mass of the gas (in g-mol¯¹) is

1. 8
2. 64
3. 96
4. 16

Answer: 2. 64

Question 66. At a given condition, 20L of SO₂ gas takes 60 for its effusion. At the same condition, the volume of 09 gas that will effuse out in 30 seconds is

1. 12.4L
2. 10.9L
3. 14.1L
4. 6.8L

Answer: 3. 14.1L

Question 67. The average velocity of the molecules of a gas at T₁K will be the same as the most probable velocity of the molecules of the gas at T₂K when

1. T₁ > r₂
2. t₂ >T₁
3. t₁=t₂
4. t₁> r₂

Answer: 2. t₂ >T₁

Question 68. Two ideal gases A and B have molar masses MA and MB g-mol-1 respectively. Volumes of the same mass of A and B are the same, and the rms velocity of A molecules is twice that of the molecules of B. If MB: MA = 2:1, then the ratio of the pressures of A to B is—

1. 4:1
2. 8:1
3. 2:1
4. 1:6

Answer: 1. 4:1

Question 69. Containing gas molecules, the percentage of molecules moving with velocities 2× 10⁴cm.s^-1 and 1 × 10^-1cm s^-1 are 30% and 45% respectively, and the rest one moving with velocity 5 × 104 cm-s^-1. The root mean square velocity of the molecules is

1. 3.7 × 10⁴cm.s^-1
2. 1.8 × 10⁴ cm.s^-1
3. 6.2 × 10³ cms^-1
4. 2.8 × 10⁴ cms^-1

Answer: 4. 2.8 × 10⁴ cms^-1

Question 70. An open vessel has a temperature of TK. When the vessel is heated at 477°C, three-fifths of the air in the vessel escapes out. What fraction of air in the vessel would have been expelled out if the vessel were heated at 900K (assume that the volume of the vessel remains unchanged on heating)

1. 4
2. 3
3. 2
4. 5

Answer: 2. 2

Question 71. Critical temperatures of the gases A, B, C and D are 126K, 155K, 304K and 356K respectively. Among these gases, the one with the strongest intermolecular forces of attraction is—

1. A
2. B
3. C
4. D

Answer: 4. D

Question 72. The volumes of two gases A and B at 0°C and 200 atm pressure are 0.112L and 0.09L respectively. Which of the following comments is true for these gases at this temperature and pressure

1. The compressibility of gases a and b are the same
2. The compressibility of a is less than that of b
3. The compressibility of a is more than that of b
4. Both gases show positive deviation from ideality

Answer: 3. Compressibility of a is more than that of b

Question 73. Which of the following correctly represents the relation between capillary rise (h) and radius of the capillary (r) —

Answer: 2.

Question 74. For CO₂ gas the P vs V isotherms at temperatures above 31.1°C are

1. Straight line
2. Rectangular hyperbolic
3. Elliptical
4. Hyperbolic

Answer: 2. Rectangular hyperbolic

Question 75. At a certain temperature, lmol of chlorine gas at 1.2 atm takes 40 sec to diffuse while 1 mol of its oxide at 2 atm takes 26.5 sec. The oxide is

1. Cl₂O
2. ClO₂
3. Cl₂O₆
4. Cl₂O₇

Answer: 1. Cl₂O

Question 76. At 10 bar pressure, a 4:1 mixture of He and CH₄ is contained in a vessel. The gas mixture leaks out through a hole present in the vessel. The mixture effusing out has an initial composition of

1. 1:1
2. 2:1
3. 4:1
4. 8:1

Answer: 4. 8:1

Question 77. A gas mixture consisting of N₂ and 3 mol of O₂ had a pressure of 2 atm at 0 °C. Keeping the volume and the temperature of the mixture constant, some amount of O₂ was removed from the mixture. As a result, the total pressure of the mixture and the partial pressure of N₂ in the mixture became 1.5 atm and 0.5 atm respectively. The amount of oxygen gas removed was

1. 8g
2. 16g
3. 32g
4. 64g

Answer: 3. 32g

Question 78. The quantity — represents

1. Mass of a gas
2. Translation energy of a gas
3. Number of moles of a gas
4. Number of molecules in a gas

Answer: 4. Number of molecules in a gas

Question 79. At STP, O₂ gas present in a flask was replaced by SO₂ under similar conditions. The mass of SO₂ present in the flask will be

1. Twice that of O₂
2. Half that of O₂
3. Equal to that of O₂
4. One-third of O₂

Answer: 1. Twice that of O₂

Question 80. The relative densities of oxygen and carbon dioxide are 16 and 22 respectively. If 37.5cm³ of oxygen effuses out in 96s, what volume of carbon dioxide will effuse out in 75s under similar conditions

1. 25cm³
2. 37.5cm³
3. 14cm³
4. 30.8cm³

Answer: 1. 25cm³

Question 81. At 27°C, the average translational kinetic energies of the molecules in 8g of CH₄,8g of O₂ and 8g of He are, e₂ and e₂ respectively and the total kinetic energies of the molecules in these gases are E₁, E₂ and E₃ respectively. Which of the following is true

1. \(\bar{\epsilon}_1=\bar{\epsilon}_2=\bar{\epsilon}_3\)
2. \(\bar{\epsilon}_3=\bar{\epsilon}_2=\bar{\epsilon}_1\)
3. E₁ = E₂ = E₃
4. E₂<E₁<E₃

Answer: 1. \(\bar{\epsilon}_1=\bar{\epsilon}_2=\bar{\epsilon}_3\)

Question 82. Several molecules of an ideal gas present in a flask of volume 2L are 10²³. The mass of each gas molecule is 6.64 × 10^-23 g and the root mean square velocity of the molecules is 4.33 × 10⁴ cm-s-1. Hence

1. The pressure of the gas is 3.27 atm
2. The average kinetic energy of each molecule is 6.23 × 10¹⁴J
3. The total kinetic energy of the molecules is 6.23 × 10⁹J
4. The total kinetic energy of the molecules is 1.492 × 10⁹ J

Answer: 2. The average kinetic energy of each molecule is 6.23 × 10¹⁴J

Question 83. In which conditions does the most probable velocity of O₂ molecules have maximum value and in which conditions does it have minimum value

1. O₂ : P = 1 atm, d (density) = 0.0081 g mL^-1
2. O₂ : P = 4 atm, V = 2L and w (mass) = 4g
3. O₂ : r=300K
4. O₂: STP

Answer: 1. O₂ : P = 1 atm, d (density) = 0.0081 g mL^-1

Question 84. The time required to effuse V mL of H₂ gas through a porous wall at a constant temperature and pressure is 20 min. Under the same conditions time required to effuse V mL of the following gases is

1. He:28.28min
2. CO₂:90.82min
3. CH₄:60.52 min
4. N₂:74.83 min

Answer: 1. He:28.28min

Question 85. At a particular temperature and pressure, if the number of moles of an ideal gas is increased by 50%, then

1. The final volume of the gas will be 1.5 times its initial volume
2. The most probable velocity of gas molecules becomes 1.5 times its initial value
3. The total kinetic energy of the gas molecules becomes 1.5 times its initial value
4. The density of gas becomes 1.5 times its initial value.

Answer: 1. Final volume of the gas will be 1.5 times its initial volume

Question 86. The pressure and temperature of a gas are P and T respectively. If the critical pressure and critical temperature of the gas are Pc and Tc respectively, then liquefaction will be possible when

1. P<PC,T<TC
2. P = PC,T=TC
3. P = PC,T>TC
4. P>PC,T=TC

Answer: 2. P = PC,T=TC

Question 87. If the orders of the values of van der Waals constants a and b for three gases X, Y and Z are X < Y < Z and Z < Y < X respectively, then

1. Liquefaction will be easier for gas than gases and z.
2. The size of the molecule, y will be in between the sizes of the molecules x and z.
3. The order of the critical temperatures of these three gases is: x< y<z.
4. The gas, z, at 0°c and 1 atm will behave most ideally.

Answer: 2. The size of the molecule, y will be in between the sizes of the molecules x and z.

Question 88. Identify the correct statements

1. At a particular temperature, the vapour pressure of dimethyl ether is greater than water because the molar mass of dimethyl ether is higher than that of water.
2. The vapour pressure of a liquid remains the same when the surface area of the liquid is increased at a given temperature.
3. The correct order of viscosity coefficient is ethylene glycol < glycerol.
4. The surface tension of water at 30°c is greater than that at 20°c.

Answer: 2. The vapour pressure of a liquid remains the same when the surface area of the liquid is increased at a given temperature.

Question 89. P(V-b) = RT equation of state is obeyed by a particular gas. Which of the given statements is correct

1. For this gas, the isochoric curves have slope = \(=\frac{R}{V-b}\)
2. The compressibility factor of the gas is less than unity.
3. For this gas, the isobaric curves have slope = r/p
4. In this gas, the attraction forces are overcome by repulsive forces.

Answer: 1. For this gas, the isochoric curves have slope = \(=\frac{R}{V-b}\)

Question 90. Four gas balloons P, Q, R and S of equal volumes containing H₂, N₂O, CO, and CO₂ respectively were pricked with a needle and immersed in a tank containing CO₂. Which of them will shrink after some time?

1. P
2. Q
3. R
4. S

Answer: 1. P

Question 91. A liquid is in equilibrium with its vapour at its boiling point. On average, the molecules in the two phases have

1. Equal total energy and potential energy.
2. Equal kinetic energy different total
3. Energy and potential
4. Energy is different from kinetic energy.

Answer: 2. Equal kinetic energy different total

Question 92. The root mean square velocity of an ideal gas in a closed vessel of fixed volume is increased from 5× 10⁴cm.s^-1 to 10 × 10⁴cm.s^-1. Which of die following statements clearly explains how the change is accomplished 

1. By heating the gas, the die temperature is quadrupled.
2. By heating die gas, the temperature is doubled by heating the gas,
3. The pressure is quadrupled by heating the gas,
4. The pressure is doubled

Answer: 1. By heating the gas, the die temperature is quadrupled.

Question 93. Which of the following pairs of gases have the same type of intermolecular force of attraction

1. Ch4, CI₂
2. SO₂,CO₂
3. HC₁, CHCI₃
4. N₂,NH₂

Answer: 1. Ch₄, CI₂

Question 94. Select the correct orders

1. Critical temperature < boyleg’s temperature < inversion temperature
2. Van der waals constant ‘a’: H₂O> nh₃ > N₂ > ne
3. Van der waals constant ‘b’: CH₄> O₂ >H₂
4. Mean free path: he > H₂ >O₂ >  N₂ > CO₂
5. All the above

Answer: 4. All the above

Question 95. Which are responsible for the liquefaction of H₂ 

1. Coulombic forces
2. London forces
3. Hydrogen bonding
4. Van der Waals forces

Answer: 2. London forces

Question 96. Which of the following gases will have the same rate of effusion under identical conditions

1. CO
2. N₂O
3. C₂H₄
4. CO₂

Answer: 2. N₂O

Question 97. Select the correct statements

1. The presence of impurities invariably increases the viscosity of a liquid.
2. In the presence of impurities, the viscosity of a liquid remains unaltered
3. The viscosity coefficient of associated liquids is larger than that of non-associated liquids.
4. Viscosity coefficients of non-associated liquids are larger than those of associated liquids.

Answer: 1. Presence of impurities invariably increases the viscosity of a liquid.

Question 98. Select the correct statements

1. Surface energy of a liquid = \(\frac{\text { force } \times \text { distance }}{\text { area }}\)
2. Surface energy can be represented as force/area
3. The addition of NaCl increases and the addition of acetone decreases the surface tension of water.
4. The addition of NaCl decreases and the addition of acetone increases the surface tension of water.

Answer: 1. Surface energy of a liquid = \(\frac{\text { force } \times \text { distance }}{\text { area }}\)

Question 99. Precisely lmol of He and 1 mol of Ne are placed in a container. Select correct statements about the system

1. Molecules of the strike the wall more frequently
2. Molecules of he have greater average
3. The molecular speed molecule of the two gases strikes the wall of the container with the same frequency
4. He has a larger pressure

Answer: 1. Molecules of he strikes the wall more frequently

Question 100. Which of the following is correct for different gases under the same condition of pressure and temperature

1. Hydrogen diffuses 6 times faster than oxygen
2. Hydrogen diffuses 2.83 times faster than methane
3. Helium escapes at a rate 2 times as fast as sulphur dioxide does
4. Helium escapes at a rate 2 times as fast as methane does

Answer: 2. Hydrogen diffuses 2.83 times faster than methane.

Question 101. For a definite mass of ideal gas at constant temperature, V versus \(\frac{1}{p}\) plot is a

1. Parabola
2. Straight line
3. Hyperbola
4. Rectangular Hyperbola

Answer: 2. Straight line

Question 102. The surface tension of water with the increase of temperature may

1. Increase
2. Decreases
3. Remain same
4. Shows irregular behaviour

Answer: 2. Decreases

Question 103. Which of the following is the unit of van der Waals gas constant

1. L₂.mol
2. L.mol¯²
3. L.mol
4. L.mol¯¹

Answer: 4. L.mol¯¹

Question 104. The cause of the spherical drop of water is

1. Surface tension
2. Viscosity
3. Hydrogen bond
4. High critical temperature of h₂O vapour

Answer: 2. Viscosity

Question 105. Which gas among the following exhibits maximum critical temperature—

1. N₂
2. O₂
3. CO₂
4. H₂

Answer: 3. CO₂

Question 106. Indicate the correct answer: The rate of diffusion of helium gas at constant temperature and pressure will be four times the rate of diffusion of the following gases

1. CO₂
2. SO₂
3. NO₂
4. O₂

Answer: 2. SO₂