Single correct · +4 / −1
The IUPAC name of [Co(NH₃)₆]Cl₃ is:
- (a) Hexamminecobalt(III) chloride
- (b) Cobalt(III) hexammine chloride
- (c) Cobalt hexammine trichloride
- (d) Amminecobalt chloride
Answer and solution
Answer (a) Hexamminecobalt(III) chloride
Solution
Chemistry ma’am · 4 steps
Name the complex ion as one word, ligands before metal, then name the chloride counter-ions.
- Cation first. The compound is an ionic salt: [Co(NH₃)₆]³⁺ is the cation and three Cl⁻ are the anions. In IUPAC names the cation always comes first, then the anion.
- Find the oxidation state. NH₃ is neutral and each chloride is -1. So x + 6(0) + 3(-1) = 0, which gives x = +3 for cobalt.
- Build the cation name. Inside the complex, ligands come before the metal. Six NH₃ ligands are hexaammine (often written hexammine), and the metal follows as cobalt(III), all as one word.
- So. The anion is named last as chloride. The number of chlorides is not stated, because the oxidation state already fixes it. The name is hexamminecobalt(III) chloride, option (a).
The idea to keep. For a coordination salt, name the cation first and the anion second. Inside the complex, ligands come before the metal, and the metal's oxidation state goes in Roman numerals.
Answer from the NTA final answer key. Solution by PrepWiser.