Question

An aqueous solution of CoCl3 6NH3 is found to be a better conductor of electri than an aqueous solution of CoCl3.4NH3. No ammonium ions are detected by the addition of H2So, to the solutions of either of these compounds. Can you explain the difference in the conductivities of two solution?

Answer 1

As coordination number of Cobalt is = 6

hence the compound formed from
                          compound  1)  CoCl3.4NH3 = [Co(NH3)4 Cl2] Cl
                          compound  2) CoCl3.6NH3 = [Co(NH3)6] Cl3

conduction depend on no. of ions outside the coordination sphere+ complex hence no. of conduction ion in compound 1 is 2(Cl and [Co(NH3)4Cl2])

and in compound 2 conduction ions are 4 (3 Cl and [Co(Nh3)6] )

hence compound 2 i.e. CoCl3.6NH3  is better conductor

Note: NH3 will also be not detected in solution because in both the compounds it is present in coordination sphere.