Question

Which has the maximum conductivity?
A. $ \left[ {Cr{{(N{H_3})}_3}C{l_3}} \right] $
B. $ \left[ {Cr{{(N{H_3})}_4}C{l_2}} \right]Cl $
C. $ \left[ {Cr{{(N{H_3})}_5}Cl} \right]C{l_2} $
D. $ \left[ {Cr{{(N{H_3})}_6}} \right]C{l_3} $

Answer 1

Hint :When ionic compounds are dissolved in an aqueous solution or in their molten state, they get dissociated into respective ions which are free to move from place to place in the solution and due to this ionic mobility, the ionic compounds in the molten state conducts electricity.

Complete Step By Step Answer:
We know that the electricity is conducted in a molten state of ionic compounds due to their free ions present in the solution. So, greater the number of ions in the solution, the greater will be the conductivity of the solid. Hence, for given complexes we need to check the number of ions which are formed on dissociation of each compound.
Dissociation of complexes given in the options take place as follows:
 $ \left[ {Cr{{(N{H_3})}_3}C{l_3}} \right] $ : This complex will not dissociate into ions because all the ligands are present within the coordination sphere which does not allow to ionize the ions in the aqueous solution.
 $ \left[ {Cr{{(N{H_3})}_4}C{l_2}} \right]Cl $ : This complex can dissociate into ions because a counterion for the coordination sphere is present within the complex. So, the reaction for dissociation for the given complex is as follows-
 $ \left[ {Cr{{(N{H_3})}_4}C{l_2}} \right]Cl \to {\left[ {Cr{{(N{H_3})}_4}C{l_2}} \right]^ + } + C{l^ - } $
Hence, the total number of ions formed in the solution for the given complex $ = 2 $ .
 $ \left[ {Cr{{(N{H_3})}_5}Cl} \right]C{l_2} $ : This complex can also dissociate into ions because the counterions for the coordination sphere are present within the complex. So, the reaction for dissociation for the given complex is as follows-
 $ \left[ {Cr{{(N{H_3})}_5}Cl} \right]C{l_2} \to {\left[ {Cr{{(N{H_3})}_5}Cl} \right]^ + } + 2C{l^ - } $
Hence, the total number of ions formed in the solution for the given complex $ = 3 $ .
 $ \left[ {Cr{{(N{H_3})}_6}} \right]C{l_3} $ : This complex will get dissociated into ions because the counterions for the coordination sphere are present within the complex. So, the reaction for dissociation for the given complex is as follows-
 $ \left[ {Cr{{(N{H_3})}_6}} \right]C{l_3} \to {\left[ {Cr{{(N{H_3})}_6}} \right]^ + } + 3C{l^ - } $
Hence, the total number of ions formed in the solution for the given complex $ = 4 $ .
So, the maximum number of ions generated in the aqueous solution by the complex $ \left[ {Cr{{(N{H_3})}_6}} \right]C{l_3} $ . Hence, it will show the maximum conductivity.
So, the correct answer is option (D).

Note :
It is important to note that the given complexes are complex salts i.e., it consists of more than one complex ion which may or may not have counterions. The complex ion consists of a metal centre which forms a coordinate bond with the ligands (the compounds which have tendency to donate electrons). These complex ions do not dissociate when dissolved in aqueous solution.