Question

With $C{r}_2{O}_3$, colour of the bead in sodium carbonate bead test:

• A.
  Red
• B.
  Blue
• C.
  Yellow
• D.
  Green

Answer 1

The correct option is C

Yellow
The reaction of chromium oxide, $C{r}_2{O}_3$with the sodium carbonate produces sodium chromate. The chromium oxide has chromium in (+3) oxidation state, which is green in colour and is reduced to (+6)oxidation state in sodium chromate, which shows a characteristic yellow colour.

$2C{r}_2{O}_3+4N{a}_{2}C{O}_3+3O_2\to 4N{a}_{2}Cr{O}_4+4C{O}_2$