Question

How will you identify $S{O}_2^{2-}$ in presence of $C{O}_3^{2-}$?

• A. by odour.
• B. color change.
• C. PH measurement.
• D. weight measurement.

Answer 1

The correct option is B color change.

$(C{O}_3^{2-}+S{O}_3^{2-})+dil.HCl\to C{O}_2+S{O}_2\text{Both gases turn lime water milky.}\text{Hence,}\text{(a) First pass the gaseous mixture into acidified}{K}_{2}C{r}_2{O}_7\text{solution. Only}S{O}_2$ $\text{reacts and turns it green.}C{r}_2{O}_7^{2-}+3S{O}_2+2H^{+}\to \underset{green}{2C{r}^{3+}}+3S{O}_4^{2-}+H_{2}O\text{(b) Gas unreacted is}C{O}_2.\text{Pass it into lime water. It turns milky.}Ca(OH{)}_2+C{O}_2\to \underset{milky}{CaC{O}_3}+H_{2}O$