What is the freezing point depression constant (K f) of nitrobenzene if a solution consisting of 0.25 mole of methylbenzene and 244 g of nitrobenzene freezes at -1.2°C? (The freezing point of pure nitrobenzene is 6°C).
a) 4.92 °C/m
b) 5.23 °C/m
c) 5.81 °C/m