Coordination Compounds: JEE Main Chemistry Question with Solution
Total number of moles of AgCl precipitated on addition of excess of AgNO3 to one mole each of the following complexes [Co(NH3)4Cl2]Cl, [Ni(H2O)6]Cl2, [Pt(NH3)2Cl2] and [Pd(NH3)4]Cl2 is
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Hint 1 of 3
Which chloride ions in a coordination compound precipitate as silver chloride upon adding aqueous silver nitrate?
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Correct answer
Addition of excess silver nitrate precipitates a total of 5 moles of silver chloride from one mole of each of the four coordination complexes.
Option analysis
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Solution
StepWorking
01given
One mole each of four coordination complexes treated with excess AgNO3:
1. [Co(NH3)4Cl2]Cl
2. [Ni(H2O)6]Cl2
3. [Pt(NH3)2Cl2]
4. [Pd(NH3)4]Cl2
02find
Total moles of AgCl precipitated from the mixture.
03strategise
According to Werner's theory, only chloride ions present in the outer coordination sphere (ionisable sphere) react with Ag+ to precipitate as AgCl. Chloride ligands inside the square brackets (coordination sphere) are non-ionisable and do not precipitate. Therefore, the moles of AgCl precipitated per mole of complex equals the number of chlorine atoms outside the brackets.
04execute
Determine moles of AgCl precipitated by each complex:
- [Co(NH3)4Cl2]Cl has 1 ionisable Cl−⟹1 mol AgCl
- [Ni(H2O)6]Cl2 has 2 ionisable Cl−⟹2 mol AgCl
- [Pt(NH3)2Cl2] has 0 ionisable Cl−⟹0 mol AgCl
- [Pd(NH3)4]Cl2 has 2 ionisable Cl−⟹2 mol AgCl
Total moles = 1+2+0+2=5.
✓verify
Double-check coordination numbers: Co(III) has 6 ligands, Ni(II) has 6, Pt(II) has 4 (square planar), Pd(II) has 4 (square planar). All formulations are chemically valid and neutral. Total outer-sphere chlorides count is precisely 1+2+0+2=5.
Hints that build this answer step by step
Which chloride ions in a coordination compound precipitate as silver chloride upon adding aqueous silver nitrate?
Only the counter-ion chloride ligands located outside the coordination sphere.
How many moles of ionizable chloride ions are released per mole of each of the four complexes: [Co(NH3)4Cl2]Cl, [Ni(H2O)6]Cl2, [Pt(NH3)2Cl2], and [Pd(NH3)4]Cl2?
1, 2, 0, and 2 moles respectively.
What is the total number of moles of AgCl precipitated from one mole of each complex combined?
Why doesn't [Pt(NH3)2Cl2] precipitate any AgCl?
Both chlorine atoms in [Pt(NH3)2Cl2] act as coordinate covalent ligands inside the coordination sphere, so they do not dissociate into free chloride ions in aqueous solution.