The volume (in mL) of $$0.1$$ M AgNO$$_3$$ required for complete precipitation of chloride ions present in $$20$$ mL of $$0.01$$ M solution of [Cr(H$$_2$$O)$$_5$$Cl]Cl$$_2$$ as silver chloride is _____.

The complex [Cr(H₂O)₅Cl]Cl₂ has:

• 1 Cl in the coordination sphere (not ionizable)
• 2 Cl⁻ as counter ions (ionizable)

Moles of complex = 0.01 × 20/1000 = 0.0002 mol

Moles of ionizable Cl⁻ = 2 × 0.0002 = 0.0004 mol

For precipitation: Ag⁺ + Cl⁻ → AgCl

Moles of AgNO₃ needed = 0.0004 mol

Volume of 0.1 M AgNO₃ = 0.0004/0.1 = 0.004 L = 4 mL

The volume is $$\mathbf{4}$$ mL.