Q. Both ${Co}^{3 +}and\ {Pt}^{4 +}\$have a coordination number of six. Which of the following pairs of complexes will show approximately the same electrical conductance for their 0.001 M. aqueous solutions?
A) ${CoCl}_{3}\ .4{NH}_{3}\ and\ {PtCl}_{4}.\ 4{NH}_{3}$
B) ${CoCl}_{3}\ .3{NH}_{3}\ and\ {PtCl}_{4}.\ 5{NH}_{3}$
C) ${CoCl}_{3}\ .6{NH}_{3}\ and\ {PtCl}_{4}.\ 5{NH}_{3}$
D) ${CoCl}_{3}\ .6{NH}_{3}\ and\ {PtCl}_{4}.\ 3{NH}_{3}$
Explanation
(c)
${Co}^{3 +}and\ {Pt}^{4 +} = 6$ coordination number
${CoCl}_{3}\ .6{NH}_{3}\ and\ {PtCl}_{4}\ .5{NH}_{3}$
$\left\lbrack Co\left( {NH}_{3} \right)_{6} \right\rbrack{Cl}_{3}\ \overset{In\ solution}{\rightarrow}\left\lbrack Co\left( {NH}_{3} \right)_{6} \right\rbrack^{3 +} + 3{Cl}^{-}$
$\left\lbrack PtCl\left( {NH}_{3} \right)_{5}\ \right\rbrack{Cl}_{3}\overset{In\ solution}{\rightarrow}\left\lbrack PtCl\left( {NH}_{3} \right)_{5} \right\rbrack^{3 +} + 3{Cl}^{-}$
Number of ionic species are same in the solution of both complexes, therefore their equimolar solutions will show same conductance.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.