JEE MainChemistrySolutions
Consider equimolar aqueous solutions of the following coordination compounds: (I) CoCl ₃ 6 NH ₃ (II) CoCl ₃ 5 NH ₃ (III) CoCl ₃ 4 NH ₃ (IV) CoCl ₃ 3 NH ₃ Assuming complete ionization of the ionizable parts, the correct increasing order of their boiling points is:
Options
- A(I) < (II) < (III) < (IV)
- B(IV) < (III) < (II) < (I)
- C(IV) < (I) < (II) < (III)
- D(I) < (III) < (II) < (IV)
Correct answer
B. (IV) < (III) < (II) < (I)
Step-by-step solution
According to Werner's coordination theory, Cobalt(III) exhibits a secondary valency (coordination number) of 6. The modern formulas for these complexes and their van't Hoff factors ( i ) upon complete ionization are: (I) [ Co ( NH ₃)₆] Cl ₃ [ Co ( NH ₃)₆]³⁺ + 3 Cl ^- Number of ions, i = 4 (II) [ Co ( NH ₃)₅ Cl ] Cl ₂ [ Co ( NH ₃)₅ Cl ]²⁺ + 2 Cl ^- Number of ions, i = 3 (III) [ Co ( NH ₃)₄ Cl ₂] Cl [ Co ( NH ₃)₄ Cl ₂]^+ + Cl ^- Number of ions, i = 2 (IV) [ Co ( NH ₃)₃ Cl ₃] Does not ionize (non-electrolyte) Number o