The degree of dissociation ($\alpha$) of a weak electrolyte, $A_x{B}_y$ is related to vant't Hoff factor (i) by the expression:

(1) $\alpha =\frac{i-1}{(x+y-1)}$

(2) $\alpha =\frac{i-1}{x+y+1}$

(3) $\alpha =\frac{x+y-1}{i-1}$

(4) $\alpha =\frac{x+y+1}{i-1}$

The Henry's law constant for the solubility of $N_2$ gas in water at 298 K is $1.0\times {10}^5$ atm. The mole fraction of $N_2$ in air is 0.8. The number of moles of $N_2$ from air dissolved in 10 moles of water at 298 K and 5 atm pressure is:

(1) $4.0\times {10}^{-4}$

(2) $4.0\times {10}^{-5}$

(3) $5.0\times {10}^{-4}$

(4) $4.0\times {10}^{-6}$

The freezing point (in $°C$) of a solution containing 0.1 g of $K_3\left[Fe{\left(CN\right)}_6\right]$ (mol wt. 329) in 100 g of water is:

($K_f=1.86<mspace\; width="1em"></mspace>K<mspace\; width="1em"></mspace>kg<mspace\; width="1em"></mspace>mo{l}^{-1}$)

1. $-2.3\times {10}^{-2}$

2. $-5.7\times {10}^{-2}$

3. $-5.7\times {10}^{-3}$

4. $-1.2\times {10}^{-2}$

On mixing, heptane and octane form an ideal solution. At 373 K, the vapour pressures of the two liquid components (heptane and octane) are 105 kPa and 45 kPa respectively. Vapour pressure of the solution obtained by mixing 25.0 g of heptane and 35 g of octane will be: (molar mass of heptane=100 g mol^-1 and of octane=114 g mol^-1)

(1) 144.5 kPa

(2) 72.0 kPa

(3) 36.1 kPa

(4) 96.2 kPa

Van't Hoff factor for $SrC{l}_2$ at 0.01 M is 1.8.  Percentage dissociation of $SrC{l}_2$ will be

(1) 70

(2) 55

(3) 40

(4) 30

Aluminium phosphate is 100% ionized in 0.01 m aqueous solution.  Hence, $∆T_b/k_b$ is

(1) 0.01

(2) 0.015

(3) 0.0175

(4) 0.02

When mercuric iodide is added to the aqueous solution of potassium iodide is 

(1) Freezing point is raised

(2) Freezing point is lowered

(3) Freezing point does not change

(4) Boiling point does not change

$K_4\left[Fe{\left(CN\right)}_6\right]$ is 50% dissociated then the value of Van't Hoff factor (i)

(1) 2

(2) 2.2

(3) 2.5

(4) 3

At a given temperature, total vapour pressure (in Torr) of a mixture of volatile components A and B is given P = 120 - 75 $x_B$.  Hence vapour pressure of pure A and B respectively (in Torr) are

(1) 120, 75

(2) 120, 195

(3) 120, 45

(4) 75, 45

An aqueous solution of non-electrolyte 'A' with molecular mass 60 contains 6 g in 500 mL and has a density equal to 1.05 g $m{L}^{-1}$.  The molality of solution  is

(1) 1.25

(2) 0.19

(3) 0.25

(4) 0.30