Write the correct IUPAC name for the complex [Cr(H $_{2}$ O) $_{4}$ Cl $_{2}$ ]Cl·2H $_{2}$ O.

medium 2 marks Class 12 · Chemistry · Coordination Compounds

Answer

tetraaquadichloridochromium(III) chloride dihydrate

The correct answer is tetraaquadichloridochromium(III) chloride dihydrate — Add the counter‑ion "chloride" and the waters of crystallisation "dihydrate". The complete name is "tetraaquadichloridochromium(III) chloride dihydrate".

Step-by-step solution

Assign oxidation state to Cr: let it be $x$ . Water is neutral, each Cl in the inner sphere is $- 1$ . The complex ion has overall charge $+ 1$ , so $x + 4 (0) + 2 (- 1) = + 1 \Rightarrow x = + 3$ .
List the ligands inside the brackets in alphabetical order, ignoring the prefixes: "chlorido" (Cl) comes before "aqua" (H $_{2}$ O).
Use the suffix –ido for the anionic ligand, giving "chlorido" and the neutral ligand is "aqua". Include the numerical prefixes: "tetraaqua" for four water molecules and "dichlorido" for two chloride ligands.
Combine the ligand part with the metal name and its oxidation state: "tetraaquadichloridochromium(III)".
Add the counter‑ion "chloride" and the waters of crystallisation "dihydrate". The complete name is "tetraaquadichloridochromium(III) chloride dihydrate".

Common mistake: Using "chloride" instead of the IUPAC suffix "chlorido" and omitting the oxidation state

Concept tested: nomenclature of coordination compounds

Published 12 September 2026 · How this solution was prepared and checked

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Write the correct IUPAC name for the complex [Cr(H2​O)4​Cl2​]Cl·2H2​O.

Step-by-step solution

Write the correct IUPAC name for the complex [Cr(H $_{2}$ O) $_{4}$ Cl $_{2}$ ]Cl·2H $_{2}$ O.