An octahedral complex with the formula CoCl₃ · nNH₃ upon reaction with excess of AgNO₃ solution gives 2 moles of AgCl. Consider the oxidation state of Co in the complex is 'x'. The value of "x+n" is __________.

Solution

Chemistry ma’am · 4 steps

Precipitated chlorides sit outside the bracket, so count what is left inside to fill six places.

1. Oxidation state. The neutral formula has three Cl⁻ ions and neutral NH₃ molecules, so cobalt is +3. That gives x = 3.
2. Read the AgCl test. Only chloride ions outside the coordination sphere react with AgNO₃. Two moles of AgCl means 2 chlorides are outside, so 1 chloride is bonded to cobalt as a ligand.
3. Fill the octahedron. An octahedral complex has coordination number 6. One place is taken by Cl⁻, so NH₃ fills the other 5, giving n = 5. The complex is [Co(NH₃)₅Cl]Cl₂.

   [Co(NH₃)₅Cl]Cl₂ + 2AgNO₃ → [Co(NH₃)₅Cl](NO₃)₂ + 2AgCl v

4. So. x + n = 3 + 5 = 8, which is option (d).

The idea to keep. In Werner-type questions, ions that precipitate are outside the bracket. Subtract the ones inside from the coordination number to find the neutral ligands.

Answer from the NTA final answer key. Solution by PrepWiser.