A 0.020 mol sample of an octahedral cobalt(III) complex of composition CoCl3.nNH3 (ammonia monodentate) is treated with excess AgNO3 and gives 5.74 g of AgCl immediately (Ag =108, Cl =35.5). The value of n is

JEE Advanced levelSingle correct optionDifficulty 3 of 3cc036

A $0.020$ mol sample of an octahedral cobalt(III) complex of composition $CoCl X_{3} \cdot n NH X_{3}$ (ammonia monodentate) is treated with excess $AgNO X_{3}$ and gives $5.74$ g of $AgCl$ immediately (Ag $= 108$ , Cl $= 35.5$ ). The value of $n$ is

Moles of AgCl

= 5.74/143.5 = 0.040

mol, which is

0.040/0.020 = 2

free chloride ions per complex. So one chloride is coordinated. Coordination number 6 then needs

6 - 1 = 5

ammonia ligands, so

n = 5

and the complex is

[Co (NH X_{3}) X_{5} Cl] Cl X_{2}