Ncert Exercises & Solutions

9.5 Specify the oxidation numbers of the metals in the following coordination entities:

(i) [Co(H₂O)(CN)(en)₂]²⁺

(ii) [CoBr₂(en)₂]⁺

(iii) [PtCl₄]^2–

(iv) K₃[Fe(CN)₆]

(v) [Cr(NH₃)₃Cl₃]

(i)

{[C o (H_{2} O) (C N) {(e n)}_{2}]}^{2 +}

Let the oxidation number of Co be x.
The charge on the complex is +2.

{[\underset{↓}{C o} \underset{↓}{(H_{2} O)} \underset{↓}{(C N)} \underset{↓}{{(e n)}_{2}}]}^{2 +}

x + 0 + (- 1) + 2 (0) = + 2

x - 1 = 2

x = + 3

(ii)

{[P t {(C I)}_{4}]}^{2 -}

Let the oxidation number of Pt be x.
The charge on the complex is −2.

{[\underset{↓}{P t} \underset{↓}{{(C l)}_{4}}]}^{2 -}

x + 4 (- 1) = - 2 x

x = + 2

(iii)

${[\underset{↓}{C o} \underset{↓}{{(B r)}_{2}} \underset{↓}{{(e n)}_{2}}]}^{2 +}$
$x + 2 (- 1) + 2 (0) = + 1$
$x - 2 = + 1$
$x = + 3$

(iv)

K_{3} [F e {(C N)}_{6}]

i.e,

{[\underset{↓}{F e} \underset{↓}{{(C N)}_{6}}]}^{3 -}

x + 6 (- 1) = - 3

x = + 3

(v)

[\underset{↓}{C r} \underset{↓}{{(N H_{3})}_{3}} \underset{↓}{C l_{3}}]

x + 3 (0) + 3 (- 1) = 0

x - 3 = 0

x = + 3