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A 0.5 percent solution of potassium choride was found to freeze at -0.24°C. The percentage dissociation of potassium chloride is__________. (Nearest integer)

(Molal depression constant for water is 1.80 K kg mol-1 and molar mass of KCl is 74.6 g mol-1)

0 2 Views | Posted 3 weeks ago
Asked by Shiksha User

  • 1 Answer

  • A

    Answered by

    alok kumar singh | Contributor-Level 10

    3 weeks ago

    0.5 % KCl solution has molality (m) = 0 . 5 × 1 0 0 0 7 4 . 5 × 9 9 . 5  

    K C l ( a q ) ? K ( a g ) + + C l ( a q ) −  

    1 - a        a          a

    And I =  ( 1 − α + α + α ) = 1 + α  


    i = Δ T f k f × m = 0 . 2 4 × 7 4 . 5 × 9 9 . 5 1 . 8 × 0 . 5 × 1 0 0 0 = 1 + α  

    1.976 = 1 + a

    ∴ α = 0 . 9 7 6  

    % = 97.6%

    the nearest 98.

Similar Questions for you

When 9.45g of ClCH2COOH is added to 500ml. of water, its freezing point drops by 0.5°C. The dissociation constant of ClCH2 COOH is x × 10-3. The value of x is__________ (Rounded off to the nearest integer)

    [ k f ( H 2 O ) = 1 . 8 6 K   k g   m o l − 1 ]         
A
alok kumar singh

Δ T f = 0 . 5 ° C

Kf = 1.86

Using, density of water = 1g / mL

i = ?

Δ T f = i k f . m           

0 . 5 = i × 1 . 8 6 × 9 . 4 5 9 4 . 5 × 5 0 0 × 1 0 0 0          

i = 1.344

Now, using α = i − 1 n − 1  

n for ClCH2COOH = 2

 a =   1 . 3 4 4 − 1 2 − 1 = 0 . 3 4 4

Using

  K a = C α 2 1 − α           

K a = 0 . 2 × ( 0 . 3 4 4 ) 3 0 . 6 6 = 3 6 × 1 0 − 3           

           So; x = 36

          

The mole fraction of glucose (C?H??O?) in an aqueous binary solution is 0.1. The mass percentage of water in it, to the nearest integer, is
R
Raj Pandey

Kindly consider the following Image 

 

When 12.2g of benzoic acid is dissolved in 100g of water, the freezing point of solution was found to be -0.93°C [ K f ( H 2 O = 1 . 8 6 K   k g   m o l − 1 ] .  The number (n) of benzoic acid molecules associated (assuming 100% association) is…………,
V
Vishal Baghel

Δ T f = K f × m × i

0.93 = 1.86 × 1 × i

i = 1 2 i = 1 + ( 1 n − 1 )

∴ n = 2

1.22 g of an organic acid is separately dissolved in 100 g of benzene (Kb = 2.6 K kg mol-1) and 100 g of acetone (Kb = 1.7 K kg mol-1). The acid is known to dimerize in benzene but remain as a monomer in acetone. The boiling point of the solution in acetone increases by 0.17°C. The increase in boiling point of solution in benzene in °C is x × 0-2. The value of x is ________. (Nearest integer)

[Atomic mass : C = 12.0, H = 1.0, O = 16.0]
V
Vishal Baghel

  Δ T b = i K b m

m = w × 1 0 0 0 M × W s o l v e n t

For acetone solution,

0 . 1 7 = 1 × 1 . 7 × 1 . 2 2 × 1 0 0 0 M × 1 0 0

For Benzene solution,

2 A c i d → ( A c i d ) 2 ∴ i = 1 / 2

Δ T b = i × K b × m

= 1 2 × 2 . 6 × 1 . 2 2 × 1 0 0 0 1 2 2 × 1 0 0 ° C

= 0 . 1 3 ° C = 1 3 × 1 0 − 2 ° C

∴ x × 1 0 − 2 = 1 3 × 1 0 − 2

∴ x = 1 3

Which one of the following 0.10 M aqueous solutions will exhibit the largest freezing point depression?
R
Raj Pandey

Δ T f = i K f m

Higher the value of i, more be Δ T f .

Glucose →i = 1

Hydrazine → I = 1

Glycine → I = 1

 KHSO4 → I = 3 ( K + H + S O 4 − − )

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