Q30 / 97 · NTA Abhyas (JEE Main) 2020 · Chemistry · Solutions

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 ?

  • Correct answer
    A
    53
  • B
    65
  • C
    84
  • D
    79

Solution

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

Hence, the correct answer is option: 'A'.

More Solutions Questions