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Ques 14

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Asked by rbhatt16 23rd August 2018, 6:29 PM
Answered by Expert
Answer:
Option C is correct.
 
Given:
 
Mole fraction of water = 0.8
 
Latent heat of fusion of ice = 1436.3 cal/mol
 
Freezing point of water = 273 K
 
We have,
 
straight K subscript straight f space equals fraction numerator RT squared over denominator 1000 space straight L subscript straight f end fraction

space space space space space equals fraction numerator 2 cross times open parentheses 273 close parentheses squared over denominator 1000 cross times open parentheses begin display style bevelled fraction numerator 1436.3 over denominator 18 end fraction end style close parentheses end fraction

straight K subscript straight f space equals space 1.87 space Kmol to the power of negative 1 end exponent kg

Let space the space no space of space moles space of space water space equals space straight N

space space space space space space the space no space of space moles space of space solute space equals space straight n space

As comma space mole space fraction space of space straight H subscript 2 straight O space equals fraction numerator straight N over denominator straight N plus straight n end fraction
space space space space space space space space space space space space
space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space equals space space 0.8

therefore mole space fraction space of space solute space equals fraction numerator straight N over denominator straight N plus straight n end fraction space

space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space equals space 0.2

therefore straight n over straight N space equals space 1 fourth

therefore space straight w over straight m cross times straight M over straight W space equals 1 fourth

fraction numerator straight w over denominator straight m cross times straight W end fraction equals fraction numerator 1 over denominator 18 cross times 4 end fraction

We space have comma

increment straight T subscript f space equals fraction numerator 1000 cross times straight K subscript straight f cross times straight w over denominator straight m cross times straight W end fraction

space space space space space space space equals fraction numerator 1000 cross times 1.87 cross times 1 over denominator 18 cross times 4 end fraction

increment straight T subscript straight f space equals space 25.97 space to the power of ring operator straight C

increment straight T subscript straight f space space equals space straight T subscript straight f space to the power of 0 space minus straight T subscript straight f space

space space space straight T subscript straight f space equals space straight T subscript straight f space to the power of 0 space minus increment straight T subscript straight f

space space space space space space space equals straight T 0 minus 25.97

space space straight T subscript straight f space space equals space minus 25.97 space to the power of ring operator straight C
The freezing point of an aqueous solution is -25.97 °
Answered by Expert 29th August 2018, 3:22 PM
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