Question

`CoS` (black) obtained in group `IV` of salt analysis is dissolved in aqua regia and is treated with an excess of `NaHCO_(3)` and then `Br_(2)` water.An apple green coloured stable complex is formed. It is:
A. sodium cobaltocarbonate
B. sodium cobaltibromide
C. sodium cobalticarbonate
D. sodium cobaltobromide

Answer 1

Correct Answer - C
`2CoS+6HCl+2HNOto3CoCl_(2)+2NO+3S+4H_(2)O`
`CoCl_(2) + 6NaHCO_(3) to Na_(4)[Co(CO_(3))_(3)]+2NaCl+3H_(2)O+3CO_(2)`
`2Na_(4) [Co(CO_(3))_(3)]+Br_(2) to 2Na_(3) underset(("Green"))([Co(CO_(3))_(3)])+2NaBr`