Question
A solution containing 0.2563 g of naphthalene (molecular mass = 128) in 50 g of carbon tetrachloride yields a boiling point elevation of 0.201∘C while a solution of 0.6216 g of an unknown solute in the same mass of the solvent gives a boiling point elevation of 0.647∘C. Find the molecular mass of unknown solute.
Answer: Option A
:
A
We know that
Kb=ΔTb×W1×Mw21000×W2
First let’s calculate value of KbforCCl4.
For CCl4;
Kb=0.201×50×1281000×0.2563=5.019kkgmol−1
Now, for calculating mass of unknown solute, we can use the same value of Kb.
Mw2=1000×Kb×W2ΔTb×W1
1000×5.019×0.62160.647×50
=96.44
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:
A
We know that
Kb=ΔTb×W1×Mw21000×W2
First let’s calculate value of KbforCCl4.
For CCl4;
Kb=0.201×50×1281000×0.2563=5.019kkgmol−1
Now, for calculating mass of unknown solute, we can use the same value of Kb.
Mw2=1000×Kb×W2ΔTb×W1
1000×5.019×0.62160.647×50
=96.44
Was this answer helpful ?
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