Given:
Molality of the solution (m) = 0.0020 m
Freezing point of the solution = −0.00732∘C
Depression in freezing point (ΔTf) = 0∘C−(−0.00732∘C)=0.00732∘C
Molal depression constant (Kf) = 1.86∘C m−1
The formula for depression in freezing point is:
ΔTf=i×Kf×m
Where i is the van't Hoff factor (which represents the number of moles of particles produced per mole of the solute).
Substituting the given values into the equation:
0.00732=i×1.86×0.0020
0.00732=i×0.00372
i=0.003720.00732≈1.967≈2
Thus, 1 mol of the ionic compound produces 2 moles of ions in the solution. (The complex most likely ionizes as: [Co(NH3)5(NO2)]Cl⇌[Co(NH3)5(NO2)]++Cl−).