MEDIUM

Earn 100

Non-ideal solutions exhibit either positive or negative deviations from Raoult's law. What are these deviations and why are they caused ? Explain with one example of each type.

Important Questions on Solutions

MEDIUM

Chemistry>Physical Chemistry>Solutions>Lowering of Vapour Pressure

300 K

, the vapour pressure of a solution containing

1

mole of

n

-hexane and

3

moles of

n

-heptane is

550 mm

Hg

. At the same temperature, if one more mole of

n

-heptane is added to this solution, the vapour pressure of the solution increases by

10 mm

Hg

. What is the vapour pressure in

mmHg

n

- heptane in its pure state______?

MEDIUM

Chemistry>Physical Chemistry>Solutions>Lowering of Vapour Pressure

Liquid

M

and liquid

N

form an ideal solution. The vapour pressures of pure liquids

M

and

N

are

450

and

700 m m H g,

respectively, at the same temperature. Then correct statements is:
(

x_{M} = M o l e f r a c t i o n o f {' M}^{'} i n s o l u t i o n;

x_{N} = M o l e f r a c t i o n o f {' N}^{'} i n s o l u t i o n;

y_{M} = M o l e f r a c t i o n o f {' M}^{'} i n v a p o u r p h a s e;

y_{N} = M o l e f r a c t i o n o f {' N}^{'} i n v a p o u r p h a s e;

)

MEDIUM

Chemistry>Physical Chemistry>Solutions>Lowering of Vapour Pressure

Vapour pressure of water at

293 K

17.535 mm Hg

. Calculate the vapour pressure of water at

293 K

when

25 g

of glucose is dissolved in

450 g

of water.

MEDIUM

Chemistry>Physical Chemistry>Solutions>Lowering of Vapour Pressure

38.4 g

of unknown substance (molar mass

384 g {mol}^{- 1}

) and

116 g

of acetone is used to prepare a solution at

313 K

. If vapour pressure of pure acetone (molar mass

58 g {mol}^{- 1}

) is

0.842

atmosphere, what is the vapour pressure of solution ?

MEDIUM

Chemistry>Physical Chemistry>Solutions>Lowering of Vapour Pressure

A solution is prepared by mixing

8.5

g of

{CH}_{2} {Cl}_{2}

and

11.95 g

{CHCl}_{3}

. If vapour pressure of

{CH}_{2} {Cl}_{2}

and

{CHCl}_{3}

298

K are

415

and

200

mm Hg respectively, the mole fraction of

{CHCl}_{3}

in vapour form is:

(M o l a r m a s s o f Cl = 35.5 g m o l^{- 1})

HARD

Chemistry>Physical Chemistry>Solutions>Lowering of Vapour Pressure

Liquids

A

and

B

form ideal solution for all compositions of

A

and

B

25^{\circ} C

. Two such solutions with

0.25

and

0.50

mole fractions of

A

have the total vapor pressures of

0.3

and

0.4

bar, respectively. What is the vapor pressure of pure liquid

B

in bar?

EASY

Chemistry>Physical Chemistry>Solutions>Lowering of Vapour Pressure

9 gram anhydrous oxalic acid (mol. Wt. = 90) was dissolved in 9.9 moles of water. If vapour pressure of pure water is

P_{1}^{o}

the vapour pressure of solution is

MEDIUM

Chemistry>Physical Chemistry>Solutions>Lowering of Vapour Pressure

A solution contains

5

moles of

X

and

5

moles of

Y

, and has a normal boiling point of

90 ° C

. The vapor pressure of pure

X

300 mm Hg

. What is the vapor pressure of pure

Y

at this temperature?

HARD

Chemistry>Physical Chemistry>Solutions>Lowering of Vapour Pressure

Which of the following statements about the composition of the vapour over an ideal 1 : 1 molar mixture of benzene and toluene is correct? Assume that the temperature is constant at

25^{o} C

. (Given vapour pressure data at

25^{o} C

, benzene = 12.8 kPa, toluene = 3.85 kPa)

MEDIUM

Chemistry>Physical Chemistry>Solutions>Lowering of Vapour Pressure

For a solution formed by mixing liquids

L

and

M

, the vapour pressure of

L

plotted against the mole fraction of

M

in solution is shown in the following figure, Here,

X_{L}

and

X_{M}

represent mole fractions of

L

and

M

, respectively, in the solution. The correct statement(s) applicable to this system is(are) -

Question Image

HARD

Chemistry>Physical Chemistry>Solutions>Lowering of Vapour Pressure

Liquids A and B form ideal solution over the entire range of composition. At temperature

T

, equimolar binary solution of liquids A and B has vapour pressure

45 T o r r

. At the same temperature, a new solution of A and B having mole fractions

x_{A} and x_{B}

, respectively, has vapour pressure of

22.5 T o r r

. The value of

\frac{x_{A}}{x_{B}}

, in the new solution is ____.

(Given that the vapour pressure of pure liquid A is

20 Torr

at temperature

T

)

HARD

Chemistry>Physical Chemistry>Solutions>Lowering of Vapour Pressure

Liquids

A

and

B

form an ideal solution in the entire composition range. At

350 K,

the vapour pressure of pure A and pure B are

7 \times 10^{3} Pa

and

12 \times 10^{3} Pa

, respectively. The composition of the vapour in equilibrium with a solution containing 40 mole percent of A at this temperature is:

MEDIUM

Chemistry>Physical Chemistry>Solutions>Lowering of Vapour Pressure

How many grams of glucose are required to prepare an aqueous solution of glucose having a vapor pressure of

23.324 mm Hg

25 ° C

100 g

of water? The vapour pressure of pure water at

25 ° C

23.8 mm Hg .

MEDIUM

Chemistry>Physical Chemistry>Solutions>Lowering of Vapour Pressure

An open beaker of water in equilibrium with water vapour is in a sealed container. When a few grams of glucose are added to the beaker of water, the rate at which water molecules :

HARD

Chemistry>Physical Chemistry>Solutions>Lowering of Vapour Pressure

Benzene and toluene form an ideal solution over the entire range of composition. The vapour pressure of pure benzene and toluene at $T (K)$ are $50 mmHg$ and $40 mmHg$ , respectively. What is the mole fraction of toluene in vapour phase when $117 g$ of benzene is mixed with $46 g$ of toluene?

(Molar mass of benzene and toluene are $78$ and $92 g {mol}^{- 1}$ , respectively)

HARD

Chemistry>Physical Chemistry>Solutions>Lowering of Vapour Pressure

The plot of total vapour pressure as a function of mole fraction of the components of an ideal solution formed by mixing liquids

X

and

Y

HARD

Chemistry>Physical Chemistry>Solutions>Lowering of Vapour Pressure

The vapour pressures of chloroform

({CHCl}_{3}),

dichloromethane

({CH}_{2} {Cl}_{2})

298 K

are

200 mmHg

and

415 mmHg

, respectively. An ideal solution is prepared by mixing

59.75 g

{CHCl}_{3}

and

21.25 g

{CH}_{2} {Cl}_{2}

, the mole fractions of chloroform and dichloromethane in vapour phase, respectively are

MEDIUM

Chemistry>Physical Chemistry>Solutions>Lowering of Vapour Pressure

The vapour pressures of pure liquids

A

and

B

are

400

and

600 mm Hg

respectively at

298 K .

On mixing the two liquids, the sum of their volumes is equal to the volume of the final mixture. The mole fraction of liquid

B

0.5

in the mixture. The vapour pressure of the final solution, the mole fractions of components

A

and

B

in the vapour phase, respectively are

MEDIUM

Chemistry>Physical Chemistry>Solutions>Lowering of Vapour Pressure

A mixture of toluene and benzene boils at

100^{o} C

. Assuming ideal behaviour, the mole fraction of toluene in the mixture is closest to [Vapour pressures of pure toluene and pure benzene at

100^{o} C

are

0.742

and

1.800

bar respectively. 1 atm

= 1.013

bar]

MEDIUM

Chemistry>Physical Chemistry>Solutions>Lowering of Vapour Pressure

A solution at

20^{o} C

is composed of 1.5 mol of benzene and 3.5 mol of toluene. If the vapour pressure of pure benzene and pure toluene at this temperature are 74.7 torr and 22.3 torr respectively, then the total vapour pressure of the solution and the benzene mole fraction in equilibrium with it will be, respectively:

Non-ideal solutions exhibit either positive or negative deviations from Raoult's law. What are these deviations and why are they caused ? Explain with one example of each type.

Important Questions on Solutions

Learn and Prepare for any exam you want !