You visited us 1 times! Enjoying our articles? Unlock Full Access!

Byju's Answer

Standard XII

Chemistry

Relative Lowering of Vapour Pressure

The total vap...

Question

The total vapour pressure of a 4 mole % solution of ammonia in water at 293 K is 50.0 torr; the vapour pressure of pure water is 17.0 torr at this temperature. Applying Henry's and Raoult's laws, the total vapour pressure for a 5 mole % solution is (in torr).

Open in App

Solution

The given data is
$P_{w a t e r}^{o}$ =17.0 torr;
$P_{t o t a l}$ (4 mole % solution) = $P_{N H_{3}} + P_{w a t e r}$ =50.0 torr
$x_{N H_{3}}$ = 0.04 and ; $x_{w a t e r}$ = 0.96
Now according to Raoult's law;
$P_{w a t e r}$ = $x_{w a t e r}$ $P_{w a t e r}^{0}$
= 0.96 $\times$ 17.0 torr = 16.32 torr, $P_{a m m o n i a} = 33.68$ torr
Now Henry's law constant for ammonia is
$K_{H}$ ( $N H_{3}$ )= $\frac{P_{N H_{3}}}{x_{N H_{3}}}$ =842 torr
Hence, for 5 mole % solution, we have $P_{N H 3}$ = $K_{H}$ $(N H_{3})$ $x_{N H_{3}}$
= (842 torr) (0.05) = 42.1 torr
$P_{w a t e r}$ = $x_{w a t e r}$ $P_{w a t e r}^{0}$ = (17 torr) (0.95) =16.15 torr
Thus, $P_{t o t a l}$ (5 mole % solution) = $P_{N H 3}$ + $P_{w a t e r}$ = 42.1 + 16.15= 58.25 torr

Suggest Corrections

Similar questions

Q. The total vapour pressure of a

4

mole

solution of

N H_{3}

in water at

293 K

50.0 t o r r

, the vapour pressure of pure water is

17.0 t o r r

at this temperature. Applying Henry's and Raoult's laws, calculate the total vapour pressure for a

5

mole

solution.

Q. At

25^{\circ}

, the total pressure of an ideal solution obtained by mixing

3

mole of

A

and

2

mole of

B

, is

184 torr

. What is the vapour pressure ( in

torr

) of pure

B

at the same temperature (Vapour pressure of

A

25^{\circ} C

200 torr

.)?

Q. The vapour pressure of pure liquid is

70

Torr at

27^{o} C

. The vapour pressure of a solution of this liquid and another liquid (mole fraction 0.2) is

84

Torr at

27^{o} C

. The vapour pressure of pure liquid

B

27^{o} C

is?

Q. At

25^{\circ} C

, the total pressure of an ideal solution obtained by mixing equimolar A and B is

200 torr

. What is the vapour pressure (in

torr

) of pure

^{'} B^{'}

at the same temperature (Vapour pressure of pure

^{'} A^{'}

25^{\circ} C

100 torr

Q. The total vapour pressure of an ideal solution obtained by mixing

4 m o l

of 'A' and

6 m o l

of 'B' at

25^{\circ} C

, is

210 t o r r

. What is the vapour pressure (in

t o r r

) of pure 'B' at the same temperature?
(Given, Vapour pressure of pure 'A' at

25^{\circ} C

250 t o r r

)

Join BYJU'S Learning Program