Question

When $FeC{r}_2{O}_4$ is fused with Sodium Carbonate in the presence of air, we get Sodium Chromate. If the filtrate from this reaction is acidified, we get:

• A. Sodium dichromate
• B. Sodium oxide
• C. Sodium chromate
• D. Potassium Dichromate

Answer 1

The correct option is A Sodium dichromate

$FeC{r}_2{O}_4$ from Chromite ore is fused with Sodium Carbonate in the presence of air/oxygen to give Sodium Chromate, Iron (III) Oxide and $C{O}_2$.
$4FeC{r}_2{O}_4+8N{a}_{2}C{O}_3+7O_2\to 8N{a}_{2}Cr{O}_4+2F{e}_2{O}_3+8C{O}_2$
In the above equation, if we add water to the products, Sodium Chromate gets completely ionized while Iron (III) Oxide is insoluble. The yellow solution of sodium chromate is filtered and acidified with acid so that orange sodium dichromate $N{a}_{2}C{r}_2{O}_7.2H_{2}O$ crystallizes out.
$2N{a}_{2}Cr{O}_4+2H^{+}\to N{a}_{2}C{r}_2{O}_7+2N{a}^{+}+H_{2}O$