A aqueous solution consisting 0-5 g KCl in 100 mL water was found to freeze at -0-24-C -Given -Kfwater- 1-86 K kg mol-1-water-1 g mL-1Choose the correct statements-

Since , ρ_water=1 g mL^ 1 Weight of water (W)=100 g Calculating Observed mol. mass of nbsp;KCl (M_B) nbsp; Δ T_f=K_f× m Here m is molality M_B= 1000 × K_ ...

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Standard XII

Chemistry

Van't Hoff Factor

A aqueous sol...

Question

A aqueous solution consisting $0.5 g K C l$ in $100 m L$ water was found to freeze at $- {0.24}^{\circ} C$ .
Given :
$(K_{f})_{water} = 1.86 K k g m o l^{- 1} ρ_{w a t e r} = 1 g m L^{- 1}$

Choose the correct statement(s):

Van't Hoff factor for the solute is 1.79

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Van't Hoff factor for the solute is 1.92

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Degree of dissociation for the solute is 0.92

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Degree of dissociation for the solute is 0.79

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Solution

The correct option is C $Degree of dissociation for the solute is 0.92$
Since ,
$ρ_{w a t e r} = 1 g m L^{- 1} Weight of water (W) = 100 g$

$Calculating Observed mol. mass of K C l (M_{B}) Δ T_{f} = K_{f} \times m Here m is molality M_{B} = \frac{1000 \times K_{f} \times w}{Δ T \times W}$
where,
$K_{f} = 1.86 K k g m o l^{- 1}$ , $weight of solute (w) = 0.5 g, W = 100 g, Δ T_{f} = (0 - (- 0.24)) K = + 0.24 K$

So,
$M_{B} = \frac{1000 \times 1.86 \times 0.5}{0.24 \times 100} = 38.75 g m o l^{- 1}$

$Theoretical molecular mass of K C l = 39 + 35.5 = 74.5 g m o l^{- 1}$

$van't Hoff factor = \frac{Theoretical molecular mass}{Observed molecular mass} i = \frac{74.5}{38.75} = 1.92$
Option (b) is correct
For dissociation
$α = \frac{i - 1}{n - 1}$

Aqueous solution of $K C l$ dissociates into two ions

$∴ n = 2$
$\Rightarrow α = \frac{1.92 - 1}{2 - 1} α = 0.92$
Option (c) is correct.

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Similar questions

Q. A aqueous solution consisting

0.5 g K C l

100 m L

water was found to freeze at

- {0.24}^{\circ} C

. Find the van't Hoff factor and degree of dissociation of the solute respectively.
Given :

(K_{f})_{water} = 1.86 K k g m o l^{- 1} ρ_{w a t e r} = 1 g m L^{- 1}

25 m L

of an aqueous solution of

K C l

was found to require

20 m L

1 M A g N O_{3}

solution when titrated using a

K_{2} C r O_{4}

as indicator. Depression in freezing point of

K C l

solution with

100

% ionisation will be:

[K_{F} = {2.0}^{\circ} m o l^{- 1} k g, m o l a r i t y = m o l a l i t y]

Q. Van't Hoff factor, (i), of a

0.5 %

(w/W) aqueous solution of

K C l

which freezes at

- {0.24}^{o}

C is:

(

K_{f}

of water

= 1.86

K kg

m o l^{- 1}

, molecular weight of

K C l

= 74.5

)

Van't Hoff factor, i, of a 0.5% (w/w) aqueous solution of KCl which freezes at

- {0.24}^{o} C

is:

[K_{f}

of water = 1.86 K kg mol

^{- 1}

, Mol.wt.of KCl = 74.5]

Q. 25 ml of an aqueous solution of KCl was found to require 20 mL of 1 M

A g N O_{3}

solution when titrated using a

K_{2} C r O_{4}

as indicator .The depression in freezing point of

K C l

solution with 100% ionization will be:
[

K_{f} = {2.0}^{o} {m o l}^{- 1} k g

and molarity =molality]

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Van't Hoff Factor

Standard XII Chemistry

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A aqueous solution consisting 0.5 g KCl in 100 mL water was found to freeze at −0.24∘C . Given : (Kf)water=1.86K kg mol−1ρwater=1 g mL−1 Choose the correct statement(s):

A aqueous solution consisting $0.5 g K C l$ in $100 m L$ water was found to freeze at $- {0.24}^{\circ} C$ .
Given :
$(K_{f})_{water} = 1.86 K k g m o l^{- 1} ρ_{w a t e r} = 1 g m L^{- 1}$

Choose the correct statement(s):