The correct option is B 0.52∘C kg mol−1
Boiling point elevation of a solution is given by,
△Tb=Kb×m
where,
△Tb is the elevation in boiling point.
Kb is molal elevation constant.
m is molality of solution.
Molality (m)=nsolute×1000Wsolventin gram
Molality (m)=wsolute×1000Msolute.Wsolventin gram
where,
wsolute is mass of solute
Wsolvent is mass of solvent
Msolute is molar mass of solute
∴
△Tb=1000Kb×wW×Mor Kb=△Tb×W×M1000×wGiven, △Tb=0.13∘C,W=240 g,M=180 and w=10.8 gKb=0.13×240×1801000×10.8=0.52∘C kg mol−1