(a) ${\mathrm{CoCl}}_{3}.4{\mathrm{NH}}_{3}$, (b) ${\mathrm{CoCl}}_{3}\cdot 5{\mathrm{NH}}_{3}$, (c) ${\mathrm{CoCl}}_{3}\cdot 6{\mathrm{NH}}_{3}$ and (d) $\mathrm{CoCl}{({\mathrm{NO}}_{3})}_{2}\cdot 5{\mathrm{NH}}_{3}$ Number of complex(es) which will exist in cis-trans form is/are

JEE Main 2022 — Chemistry Inorganic Chemistry

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(a) ${\mathrm{CoCl}}_{3}.4{\mathrm{NH}}_{3}$ ,

(b) ${\mathrm{CoCl}}_{3}\cdot 5{\mathrm{NH}}_{3}$ ,

(d) $\mathrm{CoCl}{({\mathrm{NO}}_{3})}_{2}\cdot 5{\mathrm{NH}}_{3}$

Number of complex(es) which will exist in cis-trans form is/are

Official previous-year question

Held on 28 Jun 2022 · Verified 6 Jul 2026.

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Solution

Cis-trans isomerism is a type of geometrical isomerism.This type of isomerism occurs when there is a change in spatial arrangements of ligands. Cis and trans are the two terms used for representing the position of identical ligands when they are placed adjacent and opposite

(i) ${\mathrm{CoCl}}_{3}.4{\mathrm{NH}}_{3}\Rightarrow [\mathrm{Co}{({\mathrm{NH}}_{3})}_{4}{\mathrm{Cl}}_{2}]\mathrm{Cl}$ , can exhibit cis-trans isomerism.

(ii) ${\mathrm{CoCl}}_{3}.5{\mathrm{NH}}_{3}\Rightarrow [\mathrm{Co}{({\mathrm{NH}}_{3})}_{5}\mathrm{Cl}]{\mathrm{Cl}}_{2}$ ,can't exhibit cis-trans isomerism.

(iii) ${\mathrm{CoCl}}_{3}.6{\mathrm{NH}}_{3}\Rightarrow [\mathrm{Co}{({\mathrm{NH}}_{3})}_{6}]{\mathrm{Cl}}_{3}$ ,can't exhibit cis-trans isomerism.

(IV)

$\mathrm{CoCl}{({\mathrm{NO}}_{3})}_{2}.5{\mathrm{NH}}_{3}\Rightarrow [\mathrm{Co}{({\mathrm{NH}}_{3})}_{5}\mathrm{Cl}]{({\mathrm{NO}}_{3})}_{2} \mathrm{or}{[\mathrm{Co}{({\mathrm{NH}}_{3})}_{5}{\mathrm{NO}}_{3}]}_{}\mathrm{Cl}{\mathrm{NO}}_{3}$

Both can't exhibit cis-trans isomerism.

Hence. only one complex exhibits cis-trans isomerism

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Solution

(i) ${\mathrm{CoCl}}_{3}.4{\mathrm{NH}}_{3}\Rightarrow [\mathrm{Co}{({\mathrm{NH}}_{3})}_{4}{\mathrm{Cl}}_{2}]\mathrm{Cl}$ , can exhibit cis-trans isomerism.

(ii) ${\mathrm{CoCl}}_{3}.5{\mathrm{NH}}_{3}\Rightarrow [\mathrm{Co}{({\mathrm{NH}}_{3})}_{5}\mathrm{Cl}]{\mathrm{Cl}}_{2}$ ,can't exhibit cis-trans isomerism.

(iii) ${\mathrm{CoCl}}_{3}.6{\mathrm{NH}}_{3}\Rightarrow [\mathrm{Co}{({\mathrm{NH}}_{3})}_{6}]{\mathrm{Cl}}_{3}$ ,can't exhibit cis-trans isomerism.

(IV)

Both can't exhibit cis-trans isomerism.

Hence. only one complex exhibits cis-trans isomerism

JEE Main 2022 — Chemistry Inorganic Chemistry

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JEE Main 2022 — Chemistry Inorganic Chemistry

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