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Question: Answered & Verified by Expert
At solution containing 12.5 g of non-electrolyte substance in 175 g of water gave boiling point elevation of 0.70 K. Calculate the molar mass of the substance. Molal elevation constant (Kb) for water 0.52 K kg mol-1 ?
ChemistrySolutionsJEE Main
Options:
  • A 53
  • B 65
  • C 84
  • D 79
Solution:
1564 Upvotes Verified Answer
The correct answer is: 53
ΔTb=kb×wM×1000W

M=Kb×w×1000ΔTb×W

MB=Kb×WB×1000ΔTb×WA

According to available data

Mass of solute WB=12.5 g

Mass of solute WA=175 g

Molal elevation constant Kb=0.52 K kg mol-1

Elevation in boiling point temperature ΔTb=0.70 K

M=0.52 K kg mol-1×12.5 g×10000.70 K×175 g

=53 g mol-1

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