0.001 mole of [ Co ( NH ₃ )₅ ( NO ₃ ) ( SO ₄ ) ] was passed through a cation exchanger and the acid coming out of it required 20 mL of 0.1 M NaOH for neutralisation. Thus, the complex is

Step-by-step solution

Millimoles of acid required for neutralisation aligned & =20 0.1=2 millimoles & =0.002 moles aligned If 0.001 mole is neutralising 0.002 moles of base, thus, 0.001 mole of base remains unreacted. Hence, acid coming out should be basic. aligned & [ Co ( NH ₃ )₅ ( NO ₃ ) ] SO ₄ & [ Co ( NH ₃ )₅ ( NO ₃ ]²⁺+ SO ₄²⁻ . aligned