The molality of the solution is m=1.1g267.5g/mol0.1kg=0.04112mol/kg.
The expression for the depression in the freezing point is ΔTf=iKfm
Substitute values in the above expression.
0.306=i×1.86×0.04112
i=4
Thus moles of solute particles exist in solution for each mole of solute introduced.