1. Tardigrade
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  3. Chemistry
  4. 1.2 mL of acetic acid is dissolved in water to make 2.0 L of solution. The depression in freezing point observed for this strength of acid is 0.0198° C. The percentage of dissociation of the acid is (Nearest integer) [Given: Density of acetic acid is 1.02 g mL -1 Molar mass of acetic acid is 60 g mol -1 . K f ( H 2 O )=1.85 K kg mol -1]

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Q. $1.2 \,mL$ of acetic acid is dissolved in water to make $2.0 \,L$ of solution. The depression in freezing point observed for this strength of acid is $0.0198^{\circ} C$. The percentage of dissociation of the acid is_____ (Nearest integer)
[Given : Density of acetic acid is $1.02 \,g\, mL ^{-1}$
Molar mass of acetic acid is $60\, g\, mol ^{-1}$
$\left. K _{ f }\left( H _{2} O \right)=1.85\, K \,kg \,mol ^{-1}\right]$

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Solution:

$M = d \times V =1.02 \times 1.2=1.224 gm$
Moles of acetic acid $=0.0204$ moles in $2 L$
So molality $=0.0102 mol / kg$
Now $\Delta T _{ f }= i \times K _{ f } \times M$
$i=1+\alpha$ for acetic acid
$0.0198=(1+\alpha) \times 1.85 \times 0.0102 $
$\alpha=0.04928 $
$\cong 5 \%$