EASY

Earn 100

What is abnormal molecular mass? Discuss its being in molecular association/dissociation.

Important Questions on Solutions

MEDIUM

Chemistry>Physical Chemistry>Solutions>Van't Hoff's Factor

Acetic acid dimerises when dissolved in benzene. As a result boiling point of the solution rises by

0.36 ° C,

when

100 g

of benzene is mixed with

X g

of acetic acid. In this solution, if experimentally measured molecular weight of acetic acid is

117.8

and molar elevation constant of benzene is

2.57 K kg {mol}^{- 1},

what is the weight

%

and degree of dissociation (in

%

) of acetic acid in benzene?

MEDIUM

Chemistry>Physical Chemistry>Solutions>Van't Hoff's Factor

8 g

of a non-electrolyte solute is dissolved in

114 g

n -

octane to reduce its vapour pressure to

80 %,

the molar mass (in

g {mol}^{- 1}

) of the solute is [Given that molar mass of n-octane is

114 g {mol}^{- 1}

]

EASY

Chemistry>Physical Chemistry>Solutions>Van't Hoff's Factor

An aqueous solution containing

1.0 g

of urea boils at

100.25 ° C .

The aqueous solution containing

3.0 g

of glucose in the same volume will boil at:

MEDIUM

Chemistry>Physical Chemistry>Solutions>Van't Hoff's Factor

The vapour pressure of acetone at

20^{o} C

185 torr

. When

1.2 g

of a non-volatile substance was dissolved in

100 g

of acetone at

20^{o} C

, its vapour pressure was

183 torr

. The molar mass

(g m o l^{- 1})

of the substance is:

EASY

Chemistry>Physical Chemistry>Solutions>Van't Hoff's Factor

The correct relation between the elevation in boiling point and the molar mass of a solute is: (

W_{1}

and

W_{2}

are respectively weight of solvent & solute)

MEDIUM

Chemistry>Physical Chemistry>Solutions>Van't Hoff's Factor

Two solutions

A

and

B

are prepared by dissolving

1 g

of non-volatile solutes

X

and

Y

. respectively in

1 kg

of water. The ratio of depression in freezing points for

A

and

B

is found to be

1 : 4

. The ratio of molar masses of

X

and

Y

MEDIUM

Chemistry>Physical Chemistry>Solutions>Van't Hoff's Factor

Solution of

' A'

containing

3 \cdot 42 g

of it in

100 {cm}^{3}

of water is found to be isotonic with a

6.84 %

(W / v)

solution of sucrose, what is the molar mass of '

' A' ?

(at. wt;

C = 12, H = 1, 0 = 16

)

MEDIUM

Chemistry>Physical Chemistry>Solutions>Van't Hoff's Factor

Give reasons for the following:
Measurement of osmotic pressure method is preferred for the determination of molar masses of macromolecules such as proteins and polymers.

MEDIUM

Chemistry>Physical Chemistry>Solutions>Van't Hoff's Factor

A non-volatile solute,

{}^{'}A^{'}

tetramerises in water to the extent of

80 %

2.5 g

{}^{'}A^{'}

100 g

of water, lowers the freezing point by

0.3 ° C

. the molar mass of

A

g {mol}^{- 1}

is (

K_{f}

for water

= 1.86 K kg {mol}^{- 1}

)

MEDIUM

Chemistry>Physical Chemistry>Solutions>Van't Hoff's Factor

When the same amount of the solute

' P'

and

' Q'

are separately dissolved in

500 g

water, the

Δ

T_{f}

values are

0.15 K

and

0.30 K

respectively. If the molecular weight of

{}^{'}P^{'}

80 g {mol}^{- 1}

, then the molecular weight of

{}^{'}Q^{'}

HARD

Chemistry>Physical Chemistry>Solutions>Van't Hoff's Factor

Molecules of benzoic acid

(C_{6} H_{5} COOH)

dimerise in

30 g

of benzene. '

w

g

of benzoic acid shows a depression in freezing point equal to

2 K

. If the percentage association of the acid to form dimer in the solution is

80

, then

w

is:

(

Given that

K_{f} = 5 K kg {mol}^{- 1}

, molar mass of benzoic acid

= 122 {gmol}^{- 1})

MEDIUM

Chemistry>Physical Chemistry>Solutions>Van't Hoff's Factor

Determination of the molar mass of acetic acid in benzene using freezing point depression is affected by:

MEDIUM

Chemistry>Physical Chemistry>Solutions>Van't Hoff's Factor

The boiling point of benzene is

353.23 K

. When

1.80 g

of non-volatile solute was dissolved in

90 g

of benzene, the boiling point of is raised to

354.11 K

. Calculate the molar mass of the solute. (

K_{b}

for benzene is

2.53 K Kg {mol}^{- 1}

)

EASY

Chemistry>Physical Chemistry>Solutions>Van't Hoff's Factor

The osmotic pressure of

1 L

of an aqueous solution containing

0.97 g

of an organic compound is

0.08 atm

300 K

. The molar mass of the organic compound (in

g {mol}^{- 1}

) is [Gas constant,

R = 0.08 L {atmK}^{- 1} {mol}^{- 1}

]

EASY

Chemistry>Physical Chemistry>Solutions>Van't Hoff's Factor

Give reasons for the following:
Elevation of boiling point of

1 M KCl

solution is nearly double than that of

1 M

sugar solution.

MEDIUM

Chemistry>Physical Chemistry>Solutions>Van't Hoff's Factor

Visha took two aqueous solutions — one containing 7·5 g of urea (Molar mass = 60 g/mol) and the other containing 42·75 g of substance Z in
100 g of water, respectively. It was observed that both the solutions froze at the same temperature. Calculate the molar mass of Z.

HARD

Chemistry>Physical Chemistry>Solutions>Van't Hoff's Factor

Calculate the mass of ascorbic acid

(Molar Mass = 176 g {mol}^{- 1})

to be dissolved in

75 g

of acetic acid, to lower its freezing point by

1 . 5^{°} C

(K_{f} = 3.9 K kg {mol}^{- 1})

MEDIUM

Chemistry>Physical Chemistry>Solutions>Van't Hoff's Factor

58.5 g of NaCl and 180 g

of glucose were separately dissolved in

1000 mL

of water. Identify the correct statement regarding the elevation of boiling point (b.pt.) of the resulting solutions.

EASY

Chemistry>Physical Chemistry>Solutions>Van't Hoff's Factor

In 108 g of water, 18 g of a non-volatile compound is dissolved. At

100^{o} C

the vapor pressure of the solution is 750 mm Hg. Assuming that the compound does not undergo association or dissociation, the molar mass of the compound in

g m o l^{- 1}

MEDIUM

Chemistry>Physical Chemistry>Solutions>Van't Hoff's Factor

The freezing point of a

4 %

aqueous solution of

X

is equal to the freezing point of a

12 %

aqueous solution of

Y

. If the molecular weight of

X

A

, then the molecular weight of

Y

will be

What is abnormal molecular mass? Discuss its being in molecular association/dissociation.

Important Questions on Solutions

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