Question

Which amongst the following has maximum conductivity?

• A. $\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_6\right]{\mathrm{Cl}}_3$
• B. $\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_3{\mathrm{Cl}}_3\right]$
• C. $\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_4{\mathrm{Cl}}_2\right]\mathrm{Cl}$
• D. $\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_5\mathrm{Cl}\right]{\mathrm{Cl}}_2$

Answer 1

The correct option is A

$\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_6\right]{\mathrm{Cl}}_3$

Explanation for the correct option

(A) $\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_6\right]{\mathrm{Cl}}_3$

Conductivity: -

• Here Conductivity is the ability of an aqueous solution to carry electric current.
• Conductivity can be determined by concerning the number of ions present in the molecule i.e., the higher the number of ions, the higher the conductivity.

Conductivity of $\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_6\right]{\mathrm{Cl}}_3$

• $\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_6\right]{\mathrm{Cl}}_3$ dissociates as ${\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_6\right]}^{3+}+3{\mathrm{Cl}}^{-}$
• Here the number of ions present in the complex is $1+3=4$
• Conductivity of $\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_6\right]{\mathrm{Cl}}_3$is high.

Explanation for incorrect options

B) $\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_3{\mathrm{Cl}}_3\right]$

• The number of ions present in the complex is $1$
• As the number of ions is low the conductivity is low.

(C) $\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_4{\mathrm{Cl}}_2\right]\mathrm{Cl}$

• $\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_4{\mathrm{Cl}}_2\right]\mathrm{Cl}$dissociates as ${\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_4{\mathrm{Cl}}_2\right]}^{+}+{\mathrm{Cl}}^{-}$
• The number of ions present in the complex is $1+1=2$
• Here the number of ions produced is $2$ so comparatively the conductivity is low

(D) $\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_5\mathrm{Cl}\right]{\mathrm{Cl}}_2$

• $\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_5\mathrm{Cl}\right]{\mathrm{Cl}}_2$dissociates as $[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_5\mathrm{Cl}{]}^{2+}+2{\mathrm{Cl}}^{-}$
• The number of ions present in the complex is $1+2=3$
• Here the number of ions produced is $3$ so comparatively the conductivity is low

Order of conductivity is

$\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_6\right]{\mathrm{Cl}}_3$ $>$ $\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_5\mathrm{Cl}\right]{\mathrm{Cl}}_2$ $>$ $\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_4{\mathrm{Cl}}_2\right]\mathrm{Cl}$ $>$ $\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_3{\mathrm{Cl}}_3\right]$

Therefore, the correct option is (A) $\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_6\right]{\mathrm{Cl}}_3$