## Chemistry and Chemical Reactivity (9th Edition)

a) Molality: $\Delta T_f=K_fm\rightarrow -0.542^{\circ}C=-5.12^{\circ}C/m\times m$ $m=0.106\ m$ Number of moles of the dimer: $0.106\ m\times (10/1000)kg=0.00106\ mol$ Molar mass: $0.503\ g\div 0.00106\ mol=475.2\ g/mol$ b) A portion of the dimer dissociates into two monomers, which causes the molar mass calculated to be lower than the actual.