Solutions - NCERT based PYQs

1.

The van’t Hoff factor (i) for a dilute aqueous solution of a strong electrolyte barium hydroxide is:
1. 0
2. 1
3. 2
4. 3

2. The incorrect statement among the following for an ideal solution is:
1. $\Delta H_{\text{Mix}}=0$
2. $\Delta U_{\text{Mix}}=0$
3. $\Delta P=P_{\text{obs.}}-P_{\text{(Calculated by Raoult's law)}}=0$
4. $\Delta G_{\text{Mix}}=0$

3.

If the molality of the dilute solution is doubled, the value of molal depression constant (K_f) will be-
1. Halved
2. Tripled
3. Unchanged
4. Doubled

4.

At 100 °C the vapour pressure of a solution of 6.5 g of a solute in 100 g water is 732 mm. If K_b = 0.52, the boiling point of this solution will be:
1. 100 ^oC
2. 102 ^oC
3. 103 ^oC
4. 101 ^oC

5.

Consider the following statements about the composition of the vapour over an ideal 1:1 molar mixture of benzene and toluene. The correct statement is:
Assume that the temperature is constant at 25 ^oC.
(Given, vapour pressure data at 25 °C, benzene = 12.8 kPa, toluene = 3.85 kPa)

1.	The vapour will contain a higher percentage of toluene.
2.	The vapour will contain equal amounts of benzene and toluene.
3.	Not enough information is given to make a prediction.
4.	The vapour will contain a higher percentage of benzene.

6. For an ideal solution, the non-zero value will be for:
1. $\Delta H_\text{mix}$
2. $\Delta S_\text{mix}$
3. $\Delta V_\text{mix}$
4. $\Delta P=P_{\text{observed}}-P_{\text{Raoult}}$

7.

The boiling point of 0.2 mol kg^–1 solution of X in water is greater than the equimolal solution of Y in water. The correct statement in this case is:

1.	X is undergoing dissociation in water.
2.	Molecular mass of X is greater than the molecular mass of Y.
3.	Molecular mass of X is less than the molecular mass of Y.
4.	Y is undergoing dissociation in water while X undergoes no change.

8.

The electrolyte having the same value of Van't Hoff factor (i) as that of Al₂(SO₄)₃(if all are 100% ionized) is:
1. K₂SO₄
2. K₃[Fe(CN)₆]
3. Al(NO₃)₃
4. K₄[Fe(CN)₆]

9.

The largest freezing point depression among the following 0.10 m solutions is shown by:

1.	$\mathrm{KCl}$	2.	$\mathrm{C_6H_{12}O_6}$
3.	$\mathrm{Al}_2(\mathrm{SO_4})_3$	4.	$\mathrm{K_2SO_4}$

10.

p_A and p_B are the vapour pressure of pure liquid components, A and B, respectively of an ideal binary solution.
If X_A represents the mole fraction of component A, the total pressure of the solution will be:
1. p_A + X_A (p_B-p_A)
2. p_A + X_A(p_A-p_B)
3. p_B + X_A(p_B-p_A)
4. p_B + X_A(p_A-p_B)

11.

The freezing point depression constant for water is 1.86 ^oC m^-1. If 5.00 g Na₂SO₄is dissolved in 45.0 g H₂O, the freezing point is changed by -3.82 ^oC. The Van’t Hoff factor for Na₂SO₄ is:

1.	2.63	2.	3.11
3.	0.381	4.	2.05

12.

The van’t Hoff factor, i, for a compound that undergoes
dissociation and association in a solvent is, respectively:
1. Less than one and less than one.
2. Greater than one and less than one.
3. Greater than one and greater than one.
4. Less than one and greater than one.

13.

An aqueous solution is 1.00 molal in KI. The vapour pressure of the solution can be increased by:
1. Addition of NaCl
2. Addition of Na₂SO₄
3. Addition of 1.00 molal Kl
4. Addition of water

14.

A solution of sucrose (molar mass = 342 g mol^–1) has been prepared by dissolving 68.5 g of sucrose in 1000 g of water. The freezing point of the solution obtained will be:
(k_f for water = 1.86 K kg mol^–1)
1. –0.372 ^oC
2. –0.520 ^oC
3. +0.372 ^oC
4. –0.570 ^oC

15.

A 0.0020 m aqueous solution of an ionic compound Co(NH₃)₅(NO₂)Cl freezes at -0.0073 ^oC. The number of moles of ions that 1 mol of ionic compound produces on being dissolved in water will be:
(K_f = -1.86 ^oC/m)

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

16.

0.5 molal aqueous solution of a weak acid (HX) is 20 % ionised. The lowering in the freezing point of the solution will be:
[K_f for water = 1.86 K kg mol^-1]
1. -1.12 K
2. 0.56 K
3. 1.12 K
4. -0.56 K

17.

A solution containing 10 g/dm³ of urea (molecular mass = 60 g mol^-1) is isotonic with a 5 % solution of a non-volatile solute. The molecular mass of this non-volatile solute is:

1.	25 g mol^-1	2.	300 g mol^-1
3.	350 g mol^-1	4.	200 g mol^-1

18.

1.00 g of non-electrolyte solute (molar mass 250 g mol^-1) was dissolved in 51.2 g of benzene. If the freezing point depression constant, K_f of benzene is 5.12 mol^-1 kg K, the freezing point of benzene will be lowered by:
1. 0.4 K
2. 0.3 K
3. 0.5 K
4. 0.2 K

19.

A solution of acetone in ethanol:

1.	Shows a negative deviation from Raoult's law
2.	Shows a positive deviation from Raoult's law
3.	Behaves like a near-ideal solution
4.	Obeys Raoult's law

20.

During osmosis, the flow of water through a semi-permeable membrane is:

1.	From a solution having higher concentration only.
2.	From both sides of the semi-permeable membrane with equal flow rates.
3.	From both sides of the semi-permeable membrane with unequal flow rates.
4.	From a solution having lower concentration only.

21.

For an ideal solution, the correct option is:
1. $∆_{mix}$ $G = 0$ at constant T and P
2. $∆_{mix}$ $S = 0$ at constant T and P
3. $∆_{mix}$ $V \neq 0$ at constant T and P
4. $∆_{mix}$ $H = 0$ at constant T and P

22.

Which of the following mixtures forms the maximum boiling azeotrope?

1.	Heptane + Octane	2.	Water + Nitric acid
3.	Ethanol + Water	4.	Acetone + Carbon disulphide

23.

The correct statement regarding a solution of two components A and B exhibiting positive deviation from ideal behaviour is :

1.	Intermolecular attractive force between A-A and B-B are stronger than those between A-B
2.	∆_mixH = 0 at constant T and P
3.	∆_mixV = 0 at constant T and P
4.	Intermolecular attractive forces between A-A and B-B are equal to those between A-B

24. The mixture that shows positive deviation from Raoult's law is-

1. Benzene + Toluene
2. Acetone + Chloroform
3. Chloroethane + Bromoethane
4. Ethanol + Acetone

25.

The freezing point of depression constant (K_f) of benzene is 5.12 K kg mol^–1. The freezing point depression for the solution of molality 0.078 m containing a non-electrolyte solute in benzene is:
(rounded off up to two decimal places)
1. 0.80 K
2. 0.40 K
3. 0.60 K
4. 0.20 K

26.

If 8 g of a non-electrolyte solute is dissolved in 114 g of n-octane to reduce its vapor pressure to 80 %, the molar mass (in g mol^–1) of the solute is:
[Molar mass of n-octane is 114 g mol^–1]

1.	40	2.	60
3.	80	4.	20

27.

Isotonic solutions have the same:
1. Vapour pressure
2. Freezing temperature
3. Osmotic pressure
4. Boiling temperature

28.

Vapour pressure of chloroform $\mathrm{(CHCl_3)}$ and dichloromethane $\mathrm{(CH_2Cl_2)}$ at $25 ° C$ are 200 mmHg and 41.5 mmHg respectively. Vapour pressure of the solution was obtained by mixing 25.5 g of $\mathrm{(CHCl_3)}$ and 40 g of $\mathrm{(CH_2Cl_2)}$ at the same temperature will be: (Molecular mass of $\mathrm{(CHCl_3)}$ = 119.5 u and molecular mass of $\mathrm{(CH_2Cl_2)}$ = 85 u)

1.	90.40 mm Hg	2.	119.5 mm Hg
3.	75 mm Hg	4.	173.9 mm Hg

29.

A 0.1 molal aqueous solution of a weak acid (HA) is 30 % ionized. If K_f for water is 1.86 °C/m, the freezing point of the solution will be:

1.	–0.24 °C	2.	–0.18 °C
3.	–0.54 °C	4.	–0.36 °C

30.

200 mL of an aqueous solution contains 1.26 g of protein. The osmotic pressure of this solution at 300 K is found to be 2.57 × 10^–3 bar. The molar mass of protein will be:
(R = 0.083 L bar mol^–1 K^–1):

1.	61038 g mol^–1	2.	51022 g mol^–1
3.	122044 g mol^–1	4.	31011 g mol^–1

31.

The vapour pressure of two liquids 'P' and 'Q' are 80 and 60 torr, respectively. The total vapour pressure of the solution obtained by mixing 3 moles of P and 2 moles of Q would be:
1. 68 torr
2. 140 torr
3. 72 torr
4. 20 torr

32.

A solution of urea (molar mass 56 g mol^–1) boils at 100.18 ºC at atmospheric pressure. If K_f and K_b for water are 1.86 and 0.512 K kg mol^–1 respectively, the above solution will freeze at:
1. –6.54 ºC
2. –0.654 ºC
3. 6.54 ºC
4. 0.654 ºC

33.

A solution has a 1:4 mole ratio of pentane to hexane.
The vapor pressures of the pure hydrocarbons at 20 ºC are
440 mm Hg for pentane and 120 mm Hg for hexane.
The mole fraction of pentane in the vapor phase would be:

1.	0.200	2.	0.478
3.	0.949	4.	0.786

34.

The addition of water vapour does not change the density of:
1. CCl₄
2. CS₂
3. Ether
4. Coke

35.

1 % (w/w) solution of a compound is isotonic with 5 % (w/w) sucrose (sugar) solution. The molecular weight of the compound will be:

1.	32.4	2.	68.4
3.	129.6	4.	34.2

36.

The vapour pressure of a solvent decreased by 10 mm of Hg when a non-volatile solute was added to the solvent. The mole fraction of the solute in solution is 0.2. What would be the mole fraction of the solvent if the decrease in vapour pressure is 20 mm of Hg:
1. 0.2
2. 0.4
3. 0.6
4 0.8

37.

Which colligative property provides the most accurate method for determining the molecular weight of proteins and polymers?
1. Osmotic pressure
2. Lowering of vapour pressure
3. Lowering of freezing point
4. Elevation in boiling point

38.

A solution contains a non-volatile solute of molecular mass M₂. The molecular mass of solute in terms of osmotic pressure is:
where:
m₂ → Mass of solute
V → Volume of solution
$\pi$ → Osmotic pressure
1. $M_{2} = (\frac{m_{2}}{π}) VRT$
2. $M_{2} = (\frac{m_{2}}{V}) \frac{RT}{π}$
3. $M_{2} = (\frac{m_{2}}{V}) πRT$
4. $M_{2} = (\frac{m_{2}}{V}) \frac{π}{RT}$

39.

The ideal solution indicates:

1.	A – B attraction force is greater than A – A and B – B.
2.	A – B attraction force is less than A – A and B – B.
3.	Attraction force remains the same in A – A and B – B.
4.	The volume of the solution is different from the sum of the volume of the solute and solvent.

40.

Beans get cooked earlier in a pressure cooker, because:

1.	The boiling point increases with increasing pressure
2.	The boiling point decreases with increasing pressure
3.	The extra pressure of the pressure cooker softens the beans
4.	Internal energy is not lost while cooking in a pressure cooker

41.

The following solutions were prepared by dissolving 10 g of glucose (C₆H₁₂O₆) in 250 ml of water (P₁), 10 g of urea (CH₄N₂O) in 250 ml of water (P₂) and 10 g of sucrose (C₁₂H₂₂O₁₁) in 250 ml of water (P₃). The decreasing order of osmotic pressures of these solutions is:

1.	P₂ > P₃ > P₁	2.	P₃ > P₁ > P₂
3.	P₂ > P₁ > P₃	4.	P₁ > P₂ > P₃

42.

The correct option for the value of vapour pressure of a solution at 45 $°$ C with benzene to octane in a molar ratio 3:2 is:
[At 45 $°$ C vapour pressure of benzene is 280 mm Hg and that of octane is 420 mm Hg. Assume Ideal gas]
1. 336 mm of Hg
2. 350 mm of Hg
3. 160 mm of Hg
4. 168 mm of Hg

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1.	\(\mathrm{KCl}\)	2.	\(\mathrm{C_6H_{12}O_6}\)
3.	\(\mathrm{Al}_2(\mathrm{SO_4})_3\)	4.	\(\mathrm{K_2SO_4}\)

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