Question

Potassium dichromate is prepared from:

• A. chromate obtained by the fusion of chromite ore with sodium carbonate in free access of air
• B. pyrolusite which is fused with potassium hydroxide in the presence of air
• C. iron pyrites by the fusion with potassium carbonate in presence of moisture
• D. none of these

Answer 1

Answer: (A)

The potassium chromate can be prepared by chromate ore $FeC{r}_2{O}_4$.

The various reactions given are:

(i)4$FeC{r}_2{O}_4$ + 4$N{a}_{2}C{O}_3$ +9$O_2$ $\to$ $8NaCr{O}_4$ +$2F{e}_2{O}_3$ +$4C{O}_2$ (chromite ore).

(ii)$2N{a}_{2}Cr{O}_4$ +$H_{2}S{O}_4$ $\to$ $N{a}_{2}C{r}_2{O}_7$ +$N{a}_{2}S{O}_4$ +$H_{2}O$

(iii) $2N{a}_{2}C{r}_2{O}_7$ +$2KCl$ $\to$ $2K_{2}C{r}_2{O}_7$ +$2NaCl$