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The difference between the boiling point...

The difference between the boiling point and freezing point of an aqueous solution containing sucrose in 100g of water is `105.0^@C`. IF `k_f and k_b` of water are 1.86 and `0.51 K kg mol^-1` respectively, the weight of sucrose in the solution is about

A

34.2g

B

342g

C

7.2g

D

72g

Text Solution

Verified by Experts

The correct Answer is:
D
Given `T_b-T_f= 105.0^@C`
`implies (100+ Delta T_b)-(0-DeltaT_f)=105^@C`
`therefore DeltaT_b+DeltaT_f=5`
`Delta T_b+DeltaT_F=(k_b+k_f) times m`(m= molality)
`implies 5= (1.86 +0.51) times (w times 1000)/(342 times 100)`
`therefore w=1710/23.7=72g`
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