In this question paper, it covers the important one mark question from this chapter Solution. The questions are prepared based on the book back and previous year question.

Download CBSE Class 12th Standard CBSE Chemistry question papers, sample papers, important questions, and previous year solved papers in PDF format. Get free study materials, NCERT solutions, and exam preparation resources for Class 12th Standard CBSE Chemistry

Questions:

Generic 2

6 x 2 = 12

Some liquids on mixing form 'azeotropes'. What are 'azeotropes'?

State Henry's law about partial pressure of a gas in a mixture.

In terms of osmotic pressure (\(\pi \)) and volume of the solution (V) containing n moles of the solute, van't Hoff factor (i) at temperature T = _______

Define Ebullioscopic constant or molal elevation constant.

Define 'mole fraction' of a substance in a solution.

Measurement of which colligative property is preferred for determination of molar mass.

Multiple Choice Question

24 x 1 = 24

In the depression of freezing point experiment, it is found that

(a)

The vapour pressure of the solution is less than that of pure solvent

(b)

The vapour pressure of the solution is more than that of pure solvent

(c)

Only solute molecules solidity at the freezing point

(d)

Only solvent molecules solidity at the freezing point.

The colligative properties of a solution are

(a)

\(\alpha \ molality\)

(b)

\(\alpha \ \frac { 1 }{ molecular \ mass \ of \ the \ solute } \)

(c)

proportional to each other

(d)

independent of the nature of the solute, i.e., electrolyte or non - electrolyte

Which statements are true about osmotic pressure (\(\pi \) )volume (V) and temperature (T) ?

(a)

\(\pi \alpha \frac { 1 }{ V } if \ T \ is \ constant\)

(b)

\(\pi \alpha T\quad if \ V \ is \ constant\)

(c)

\(\pi \alpha V \ if \ T \ is \ costant\)

(d)

\(\pi V \ is \ constant \ if \ T \ is \ constant\)

10.

The vapour pressure of a dilute solution of a solute is not influenced by

(a)

nature of the solute if it is non - electrolyte

(b)

mole fraction of the solute

(c)

melting point of the solute

(d)

degree of dissociation of the solute

11.

If P^o and P_s are the vapour pressures of the solvent and its solution respectively and N₁ and N₂ are the mole fractions of the solvent and solute respectively, then

(a)

P_S = P^oN₂

(b)

P^o - P_S = P^oN₂

(c)

P_S = P^oN₁

(d)

(P^o - P_S)/P_S = N₁/(N₁ + N₂).

12.

The volumes of 4 N HCI and 10 N HCI required to make 1 litre of 6 N HCI are

(a)

0.75 litre of 4 N HCI and 0.25 litre of 10 N HCI

(b)

0.25 litre of 4 N HCI and 0.75 litre of 10 N HCI

(c)

0.67 litre of 4 N HCI and 0.33 litre of 10 N HCI

(d)

0.80 litre of a N HCI and 0.20 litre of 10 N HCI

(e)

0.50 litre of 4 N HCI and 0.50 litre of 10 N HCI

13.

Which following factor (s) affect the solubility of a gaseous solute in the fixed volume of liquid solvent ?
(i) nature of solute
(ii) temperature
(iii) pressure

(a)

(i) and (iii) at constant T

(b)

(i) and (ii) at constant P

(c)

(ii) and (iii) only

(d)

(iii) only

14.

K_H value for Ar(g), CO₂(g), HCHO (g) and CH₄ (g) are 4.39,1.67,1.83 x 10^-5 and 0.413 respectively. Arrange these gases in the order of their increasing solubility.

(a)

\( \mathrm{HCHO}<\mathrm{CH}_4<\mathrm{CO}_2<\mathrm{Ar}\)

(b)

\( \mathrm{HCHO}<\mathrm{CO}_2<\mathrm{CH}_4<\mathrm{Ar} \)

(c)

\( \mathrm{Ar}<\mathrm{CO}_2<\mathrm{CH}_4<\mathrm{HCHO} \)

(d)

\( \mathrm{Ar}<\mathrm{CH}_4<\mathrm{CO}_2<\mathrm{HCHO} \)

15.

On the basis of the information given below mark the correct option.
Information: On adding acetone to methanol some of the hydrogen bonds between methanol molecules break.

(a)

At specific composition, methanol - acetone mixture will form minimum boiling azeotrope and will show positive deviation from Raoult's law.

(b)

At specific composition, methanol - acetone mixture forms maximum boiling azeotrope and will show positive deviation from Raoult's law

(c)

At specific composition methanol - acetone mixture will form minimum boiling azeotrope and will show negative deviation from Raoult's law

(d)

At specific composition methanol - acetone mixture will form maximum boiling azeotrope and will show negative deviation from Raoult's law

16.

If two liquids A and B form minimum boiling azeotrope at some specific composition, then .................... .

(a)

A - B interactions are stronger than those between A - A or B - B

(b)

vapour of solution increases because more number of molecules of liquids A and B can escape from the solution.

(c)

vapour pressure of solution decreases because less number of molecules of only one of the liquids escape from the solution.

(d)

A - B interactions are weaker than those between A - A or B - B.

17.

The value of Henry's constant K_H is ____________________.

(a)

greater for gases with higher solubility

(b)

greater for gases with lower solubility

(c)

constant for all gases

(d)

not related to the solubility of gases

18.

At a given temperature, osmotic pressure of a concentrated solution of a substance .............. .

(a)

is higher than that at a dilute solution

(b)

is lower than that of a dilute solution

(c)

is same as that of a dilute solution

(d)

can not be compared with osmotic pressure of dilute solution.

19.

The unit of ebullioscopic constant is __________________.

(a)

K kg mol^-1 or K (molality)^-1

(b)

mol kg K^-1 or K^-1 (molality)

(c)

kg mol^-1 K^-1 or K^-1 (molality)^-1

(d)

K mol kg^-1 or K (molality)

20.

Considering the formation, breaking and strength of hydrogen bond, predict which of the following mixtures will show a positive deviation from Raoult's law?

(a)

Methanol and acetone

(b)

Chloroform and acetone

(c)

Nitric acid and water

(d)

Phenol and aniline

21.

On dissolving sugar in water at room temperature, solution feels cool to touch. Under which of the following cases dissolution of sugar will be most rapid ?

(a)

Sugar crystals in cold water

(b)

Sugar crystals in hot water

(c)

Powdered sugar in cold water

(d)

Powdered sugar in hot water

22.

Which of the following units is useful in relating concentration of solution with its vapour pressure ?

(a)

mole fraction

(b)

parts per million

(c)

mass percentage

(d)

molality

23.

The osmotic pressure of 0.1 M aqueous solution of NaCl is ................ Osmotic pressure of 0.1 M aqueous solution of glucose

(a)

equal to

(b)

less than

(c)

half of

(d)

nearly double

24.

A 5% solution of cane sugar (molar mass 342) is Isotonic with 1% of a solution of an unknown solute. The molar mass of unknown solute in g/mol is

(a)

136.2

(b)

171.2

(c)

68.4

(d)

34.2

25.

Camphor is often used in molecular mass determination because

(a)

it is readily available

(b)

it has a very high cryoscopic constant

(c)

it is volatile

(d)

it is solvent for organic substances

26.

The molal freezing point constant of water is 1.86^o C/M. Therefore the freezing point of 0.1 M NaCl solution in water is expected to be

(a)

- 1.86^oC

(b)

- 0.186^oC

(c)

- 0.372^oC

(d)

+ 0.372^oC

27.

The system that forms maximum boiling azeotrope is

(a)

carbon disulphide-acetone

(b)

benzene-tolune

(c)

acetone-chloroform

(d)

n-hexane-n-heptane

28.

Which one of the following gases has the lowest value of the Henry's law constant ?

(a)

N₂

(b)

(c)

H₂

(d)

CO₂

29.

5ml of 1 N HCI, 20ml of N/2 H₂SO₄ and 30ml of N/3 HNO₃ are mixed together and the volume made to one litre. The normality of the resulting solution is

(a)

N/5

(b)

N/10

(c)

N/20

(d)

N/40

30.

Molarity of the liquid HCL if density of the solution is 1.17 g/cc is

(a)

36.5

(b)

18.25

(c)

32.05

(d)

42.10

Fill up / 1 Marks

16 x 1 = 16

31.

Rast method is based upon the use of ............ as solvent whose molal depression constant is ................ .

32.

The molal depression constant of water is ............ while that of benzene is ................. .

33.

The vapour pressure of water at 100^oC is ......... bar.

34.

The best colligative property to determine the molecular masses of polymers is ........... .

35.

People taking a lot of salt develop swelling or puffiness of their tissues. This disease is called ............ .

36.

The shrinking of a plant or animal cell due to outflow of water is called ............. .

37.

The rupturing of a plant or animal cell due to flow of water into it is called ............ .

38.

Solutions having the same osmotic pressure are called ........... and they have same ............. .

39.

The semipermeable membrane generally used in the reverse osmosis is made up of ............... .

40.

A non-ideal solution showing negative deviations forms an azeotrope with ................. boilind point (lowest or highest).

41.

The constant boiling mixture of two miscible liquids of a definite mole fraction is called .............. .

42.

For a non-ideal solution showing positive deviations, \({ \Delta V }_{ mixing }\) is ....................... and \({ \Delta H }_{ mixing }\) is ............ .

43.

The variation of vapour pressure with temperature is quantitatively studied by ............... equation.

44.

The solubility of a solute decreases with increase of temparature if dissolution is .............. .

45.

An ionic compound dissolves in water if .............. energy is greater than ............ energy.

46.

Molality of a solution is .............. of the solute in .............. of the .................. .

Visit QB365-SLMS - https://www.qb365.in/slms/

Answers Key:

Generic 2

6 x 2 = 12

Azeotropes: Binary mixtures having same composition in liquid and vapour phase and boil at a constant temperature.

Henry's law states that the mass of a gas dissolved in given volume of the liquid at constant temperature depends upon the pressure applied.

\(\pi=i \frac{n}{V} R T \text { or } i=\frac{\pi V}{n R T}\)

Molal Elevation Constant (Ebullioscopic Constant:) It is equal to elevation in boiling point of 1 molal solution, i.e. 1 mole of solute is dissolved in 1 kg of solvent. It is also called ebullioscopic constant. The units of k_b is K/m or ^oC/m or K kg mol^-1, where 'm' is molality.

Mole fraction of a substance is defined as the ratio of number of moles of substance to the total number of moles of solute and solvent.

Osmotic pressure.

Multiple Choice Question

24 x 1 = 24

(a)
The vapour pressure of the solution is less than that of pure solvent

(a)
\(\alpha \ molality\)

(a)
\(\pi \alpha \frac { 1 }{ V } if \ T \ is \ constant\)

10.

(a)
nature of the solute if it is non - electrolyte

11.

(b)
P^o - P_S = P^oN₂

12.

13.

(b)
(i) and (ii) at constant P

14.

15.

(a)
At specific composition, methanol - acetone mixture will form minimum boiling azeotrope and will show positive deviation from Raoult's law.

16.

Minimum boiling azeotrope is formed when actual vapour pressure in higher than expected, i.e., solution shows +ve deviation from Raoult's law which is so when A - B interactions are weaker than A - A or B - B interactions.

17.

(b)
greater for gases with lower solubility

18.

\(\pi =CRT,i.e.,\pi \alpha C\)

19.

(a)
K kg mol^-1 or K (molality)^-1

20.

(a)
Methanol and acetone

21.

As solution is cool to touch, dissolution is endothermic. Hence, high temperature will favour dissolution. Further, powered sugar has large surface area and will dissolve faster.

22.

\(\frac { { p }^{ o }-{ p }_{ s } }{ { p }^{ o } } ={ x }_{ 2 }\) (mole fraction of solute in solution) - Raoult's law.

23.

(d)
nearly double

24.

25.

Camphor has a very high cryoscopic constant (=39.7^o). Hence, It gives a large depression in melting point when an organic solute is dissolved in it.

26.

\(NaCl\longrightarrow { Na }^{ + }+{ Cl }^{ - },i=2\\ \Delta { T }_{ f }={ iK }_{ f }m=2\times 1.86\times 0.1={ 0.372 }^{ o }C,\\ { T }_{ f }={ 0.372 }^{ o }C.\)

27.

Acetone-chloroform mixture shows negative deviation from Raoult's law. Hence, for a particular composition, it has lowest vapour pressure and maximum boiling point.

28.

Higher the solubility, lower is K_H. As CO₂ has maximum solubility, its K_H is lowest.

29.

\({ N }_{ 1 }{ V }_{ 1 }+{ N }_{ 2 }{ V }_{ 2 }+{ N }_{ 3 }{ V }_{ 3 }={ N }_{ 4 }{ V }_{ 4 }={ N }_{ 4 }({ V }_{ 1 }+{ V }_{ 2 }+{ V }_{ 3 })\)

30.

Density 1.17 g/cc means conc. = 1170 g L^-1 = 1170/36.5 M = 32.05 M

Fill up / 1 Marks

16 x 1 = 16

31.