The number of chloride ions produced by one formula unit of the complex tetraamminedichloridoplatinum(IV) chloride in an aqueous solution is
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 2
In a coordination compound, the ligands inside the square bracket are bound to the metal and do not ionise. Only the counter ions outside the bracket are set free in water.
The name gives the formula. Tetraammine = four \( \ce{NH3} \) ligands, dichlorido = two \( \ce{Cl^-} \) ligands, platinum(IV) = Pt in the +4 state. Charge on the coordination entity: +4 + 4(0) + 2(−1) = +2, so two chloride counter ions balance it:
\( \displaystyle \ce{[PtCl2(NH3)4]Cl2} \)
In water only the two outer chlorides separate; the two chlorido ligands stay bonded to platinum:
\( \displaystyle \ce{[PtCl2(NH3)4]Cl2 -> [PtCl2(NH3)4]^2+ + 2Cl^-} \)
One formula unit gives 2 chloride ions.
NCERT (2026-27 edition):
5.1 Werner’s Theory of Coordination Compounds – “2. The primary valences are normally ionisable and are satisfied by negative ions.
3. The secondary valences are non ionisable. These are satisfied by neutral molecules or negative ions. … The species within the square bracket are coordination entities or complexes and the ions outside the square bracket are called counter ions.”