Question

Which of the following has least conductivity in aqueous solution?
A) \[{\text{CO}}{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)_{\text{4}}}{\text{C}}{{\text{l}}_{\text{3}}}\]
B) \[{\text{CO}}{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)_3}{\text{C}}{{\text{l}}_{\text{3}}}\]
C) \[{\text{CO}}{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)_5}{\text{C}}{{\text{l}}_{\text{3}}}\]
D) \[{\text{CO}}{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)_6}{\text{C}}{{\text{l}}_{\text{3}}}\]

Answer 1

Hint:Conductivity of the substance is not but its ability to conduct the electricity.
The numbers of the ions area measure the conductivity of the substance in the case of the solution.
In the case of the electrons, the conductivity is because of the free electrons present in the metal.
In the case of the solution, as the numbers of the ions increase conductivity also increases.

Complete answer:
The conductivity of the substance in the aqueous solution depends on the number of ions produced by the substance in the aqueous solution.
As the number of the ions increases, conductivity also increases.
\[{\text{CO}}{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)_{\text{4}}}{\text{C}}{{\text{l}}_{\text{3}}}\]in aqueous solution is dissociated as follows:
\[{\text{CO}}{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)_{\text{4}}}{\text{C}}{{\text{l}}_{\text{3}}} \rightleftarrows {\left[ {{\text{CO}}{{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)}_{\text{4}}}{\text{C}}{{\text{l}}_{\text{2}}}} \right]^ + }\left( {{\text{aq}}} \right){\text{ + C}}{{\text{l}}^{\text{ - }}}\left( {{\text{aq}}} \right)\]
Here, the number of ions produced are two.
\[{\text{CO}}{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)_3}{\text{C}}{{\text{l}}_{\text{3}}}\] in aqueous solution is not dissociated into ions in the aqueous solution
\[{\text{CO}}{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)_5}{\text{C}}{{\text{l}}_{\text{3}}}\]in aqueous solution is dissociated as follows:
\[{\text{CO}}{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)_5}{\text{C}}{{\text{l}}_{\text{3}}} \rightleftarrows {\left[ {{\text{CO}}{{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)}_5}{\text{Cl}}} \right]^{2 + }}\left( {{\text{aq}}} \right){\text{ + }}\,{\text{2C}}{{\text{l}}^{\text{ - }}}\left( {{\text{aq}}} \right)\]
Here, the number of ions produced are three.
\[{\text{CO}}{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)_6}{\text{C}}{{\text{l}}_{\text{3}}}\]in aqueous solution is dissociated as follows:
\[{\text{CO}}{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)_6}{\text{C}}{{\text{l}}_{\text{3}}} \rightleftarrows {\left[ {{\text{CO}}{{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)}_6}} \right]^{3 + }}\left( {{\text{aq}}} \right){\text{ + }}\,3{\text{C}}{{\text{l}}^{\text{ - }}}\left( {{\text{aq}}} \right)\]
Here, the number of ions produced are three.
The least conductivity is shown by the substance which remains undissociated in an aqueous solution or which produces the least numbers of the ions in the aqueous solution.
Here, option(A) \[{\text{CO}}{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)_{\text{4}}}{\text{C}}{{\text{l}}_{\text{3}}}\] is incorrect.
Now, option(B) \[{\text{CO}}{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)_3}{\text{C}}{{\text{l}}_{\text{3}}}\] is the correct answer to the given question. Because it remains undissociated in the aqueous solution hence, possesses the least conductivity.
Option(C) \[{\text{CO}}{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)_5}{\text{C}}{{\text{l}}_{\text{3}}}\] is also incorrect.
Option(D) \[{\text{CO}}{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)_6}{\text{C}}{{\text{l}}_{\text{3}}}\] is also incorrect.

Hence,the correct option is B.

Note:As per Werner’s theory, there are two types of valence present in the compounds that is primary valence and secondary valence.Primary valence is ionisable and it is nothing but the oxidation number of the metal in the compound.
The secondary valence represents the coordination number of the metal and in the given compounds.
Here, all given are the compounds of the cobalt in which the secondary valence of the cobalt is six and it is the coordination number of the cobalt.