Arrange the given coordination compounds in increasing order of the number of ions produced in aqueous solution by them:
A. [Co(NH3)5(SO4)]Cl
B. K3[Fe(C2O4)3]
C. [Pt(NH3)2Cl(NO2)]
D. [Co(NH3)5(NO2)](NO3)2
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → C, A, D, B
When a coordination compound dissolves in water, the species inside the square bracket stay together as one complex ion. Only the counter ions written outside the bracket separate. So the number of ions is: one complex ion + the number of counter ions. A complex with no counter ion is neutral and gives no ions at all.
Matching the given compounds:
(C) \( \ce{[Pt(NH3)2Cl(NO2)]} \): neutral complex, 0 ions
(A) \( \ce{[Co(NH3)5(SO4)]Cl} \): 2 ions
(D) \( \ce{[Co(NH3)5(NO2)](NO3)2} \): 3 ions
(B) \( \ce{K3[Fe(C2O4)3]} \): 4 ions
\( \displaystyle \ce{[Co(NH3)5(SO4)]Cl -> [Co(NH3)5(SO4)]^+ + Cl^-} \)
\( \displaystyle \ce{[Co(NH3)5(NO2)](NO3)2 -> [Co(NH3)5(NO2)]^2+ + 2NO3^-} \)
\( \displaystyle \ce{K3[Fe(C2O4)3] -> 3K^+ + [Fe(C2O4)3]^3-} \)
Shortcut: The neutral complex (C) gives no ions and \( \ce{K3[Fe(C2O4)3]} \) (B) gives the most. Only Option (4) starts with (C) and ends with (B).