Match the entries of column I with appropriate entries of column II and choose the correct option out of the four options given.
| Column I (Compound) | Column II (Oxidation state of Co) |
| (a) [Co(NCS)(NH3)5](SO3) | (i) +4 |
| (b) [Co(NH3)4Cl2]SO4 | (ii) 0 |
| (c) Na4[Co(S2O3)3] | (iii) +2 |
| (d) [Co2(CO)8] | (iv) +3 |
Answer & explanation
Correct answer: option 4
(a) [Co(NCS)(NH3)5](SO3) = x - 1 + 0 = +2 ⇒ x = 3
(b) [Co(NH3)4Cl2]SO4 = x + 0 - 2 = +2 ⇒ x = 4
(c) Na4[Co(S2O3)3] = x - 6 = -4 ⇒ x = +2
(d) [Co2(CO)8] = 2x + 0 = 0 ⇒ x = 0