Solutions Test 42

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Solutions Test 42

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Question 1
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A liquid mixture of A and B (assume ideal solution ) is placed in a cylinder and piston arrangement . The piston is slowly pulled out isothermally so that the volume of liquid decreases and that of vapour increases. at the instant when the quantity of the liquid still remaining is negligibly small, the mole fraction of 'A' in the vapour is 0.4 .If $$ P^0_A = 0.4 atm , P^0_B = 1.2 atm $$ at this temperature, the total pressure at which the liquid has almost evaporated is ?

A
0.667 atm

B
1.5 atm

C
0.8 atm

D
0.545 atm

Solution
Question 2
1 / -0

Liquids A and B from an ideal solution. A certain solution of A and B contains 25 mole percent of A whereas the vapours in the equilibrium with the solution at 298 K contains 50 mole per cent of A. The ratio of vapour pressures of pure A to that of pure B at 298 K , is

A
1 :1

B
3 : 1

C
1 :3

D
2 :1

Solution
Question 3
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For each of the following dilute solutions van't Hoffs factor is equal of 3 except

A
$$ Na_2SO_4 $$

B
$$ CaF_2 $$

C
$$ K_3PO_4 $$

D
$$ (NH_4)_2CO_3 $$

Solution
Question 4
1 / -0

Liquids A and B from an ideal solution. the plot of $$ \dfrac {1}{X_A} (y-axis) \,vs \,\dfrac {1}{Y_A }(x\, axis ) $$ is linear whose slope and intercept , respectively, are given as

A
$$ \dfrac {P^0_A }{ P^0_B} , \dfrac { P^0_A - P^0_B}{P^0_B} $$

B
$$ \dfrac {P^0_A }{ P^0_B} , \dfrac { P^0_B - P^0_A}{P^0_B} $$

C
$$ \dfrac {P^0_B }{ P^0_A} , \dfrac { P^0_A - P^0_B}{P^0_B} $$

D
$$ \dfrac {P^0_B }{ P^0_A} , \dfrac { P^0_A - P^0_B}{P^0_A} $$

Solution

The plots $$\frac{1}{X_A}$$ vs $$\frac{1}{Y_A}$$ where $$X_A$$ and $$Y_A$$ are the mole fraction of liquid A in liquid and vapour phase respectively) is linear with slope and intercepts equal to $$P_{A}^{0}\setminus P_{B}^{0}$$ and $$\frac{P_B^0-P_A^0}{P_B^0}$$ respectively
$$P_{A}^{'}=P_{A}^{0}\times X_{A}$$ and $$P_{B}^{'}=P_{B}^{0}\times X_{B}$$
$$P_{A}^{'}=P_{M}\times Y_{A}$$ and $$P_{B}^{'}=P_{M}\times Y_{B}$$
$$\therefore \frac{P_A}{Y_A}=\frac{P_B}{Y_B}$$
or
$$\frac{P_A^0\times X_A}{Y_A}=\frac{P_B^0\times X_B}{Y_B}=\frac{P_B^0 \times (1-X_A)}{1-Y_A}$$
or
$$\frac{P_B^0}{X_A}=\frac{P_A^0}{Y_A}+(P_B^0-P_A^0)$$
or
$$\frac{1}{X_A}=\frac{1}{Y_A}\times \frac{P_A^0}{P_B^0}+\frac{P_B^0-P_A^0}{P_B^0}$$
or
$$y=mx+C$$

$$\therefore Slope=m=\frac{P_A^0}{P_B^0}$$ and Intercept $$C=\frac{P_B^0-P_A^0}{P_B^0}$$
Hence the correct answer is [B}.
Question 5
1 / -0

The limiting value of van't Hoff's factor for $$ Na_2SO_4 $$ is

A
2

B
3

C
4

D
5

Solution
Question 6
1 / -0

Directions For Questions

Benzene and toluene form an ideal solution. A liquid solution is formed by mixing 10 moles each of benzene and toluene at 300 K and 200 mmHg pressure. At 300 K, the vapour pressures of pure benzene and toluene are 100 and 40 mm Hg, respectively

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At what pressure half of the total moles of liquid solution will vaporize ?

A
567.14 mm Hg

B
63.25 mm Hg

C
70 mm Hg

D
66.67 mm Hg
Question 7
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The vapour pressure of pure liquid A at $$ 80^0 C $$ is

A
807.4 mm

B
511.1 mm

C
755.6 mm

D
533.3 mm
Question 8
1 / -0

Directions For Questions

Benzene and toluene form an ideal solution. A liquid solution is formed by mixing 10 moles each of benzene and toluene at 300 K and 200 mmHg pressure. At 300 K, the vapour pressures of pure benzene and toluene are 100 and 40 mm Hg, respectively

...view full instructions

If the pressure over the mixture at 300 K is reduced at what pressure does the first vapour form?

A
40 mm Hg

B
70 mm Hg

C
100 Mm Hg

D
199 mmHg

Solution
Question 9
1 / -0

Directions For Questions

Benzene and toluene form an ideal solution. A liquid solution is formed by mixing 10 moles each of benzene and toluene at 300 K and 200 mmHg pressure. At 300 K, the vapour pressures of pure benzene and toluene are 100 and 40 mm Hg, respectively

...view full instructions

If the pressure is reduced further, at what presure does the trace of liquid disppear?

A
57.14 mm Hg

B
40 Mm Hg

C
100 mm Hg

D
66.67 mm Hg

Solution
Question 10
1 / -0

Directions For Questions

The composition of vapour over a binary ideal solution is determined by the composition of the liquid . $$ X_A and Y_A $$ are the mole fraction of A i the liquid and vapour at equilibrium respectively.

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The vapour pressure of the solution this composition is:

A
$$ \sqrt { P^0_A .P^0_B } $$

B
$$ ( P^0_A - P^0_B ) $$

C
$$ ( P^0_A + P^0_B ) $$

D
$$ 0.5 ( P^0_A + P^0_B ) $$

Solution