Question

If 0.2 molal aqueous solution of a monobasic weak acid is 40% dissociated then the freezing point of the solution will be (Kf of water = 1.86 K kg mol–1)

Answer 1

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Here is Your Answer..!!
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↪ACtually welcome to the concept of the SOLUTIONS

↪⭐♢Tf = i kf m.. ( DEPRESSION IN THE FREEZING POINT )

↪since here The ...

↪VANT HOFF FACTOR (i) = 1+ 0.4 = 1.4

↪so applying the formula we get as ...

↪Delta Tf = (1.4)(1.86)(0.2)

↪Delta Tf = 0.5208

↪so the real temperature was 0 - 0.5208 = -0.52 °C
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Answer 2

ASSALAMUALAIKUM

dissociation reaction for weak acid:-

HX ⇄ H⁺ + X⁻ 

at equilibrium , α dissociation happened

according to vant haff factor,

i = 1-α +α +α = 1+α

and it is 40% ionised

α = 40/100 = 0.4

i = 1+0.4 = 1.4

Use formulae :- ΔTf= i*kf*m

ΔTf = 1.4*1.86*0.2

0.52°C



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