Question

The fusion of chromite ore $\left(FeC{r}_2{O}_4\right)$ with $N{a}_{2}C{O}_3$ in air gives a yellow solution upon addition of water. Subsequent treatment with $H_{2}S{O}_4$ produces an orange solution. The yellow and orange colours, respectively, are due to the formation of:

• A. $N{a}_{2}Cr{O}_4$ and $N{a}_{2}C{r}_2{O}_7$
• B. $C{r}_2(C{O}_3{)}_3$ and $F{e}_2(S{O}_4{)}_3$
• C. $Cr(OH{)}_3$ and $N{a}_{2}Cr{O}_4$
• D. $Cr(OH{)}_3$ and $N{a}_{2}C{r}_2{O}_7$

Answer 1

Answer: (A)

$4FeC{r}_2{O}_4+8N{a}_{2}C{O}_3+7O_2\to 8N{a}_{2}Cr{O}_4+2Fe{O}_3+8C{O}_2$

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

Yellow -----> $N{a}_{2}Cr{O}_4$

Orange ----> $N{a}_{2}C{r}_2{O}_7$