Question

If addition of conc. $H_{2}S{O}_4$ is made to an unknown salt, a colourless and odourless gas is produced then which of the following can be present?

• A. $C{O}_3^{2-}$
• B. $C{l}^{-}$
• C. $N{O}_3^{-}$
• D. $S^{2-}$

Answer 1

The correct option is A $C{O}_3^{2-}$

Confirmation Test for $C{O}_3^{2-}$
$N{a}_{2}C{O}_3+H_{2}S{O}_4\to N{a}_{2}S{O}_4+H_{2}O+C{O}_2\uparrow$
The evolution of colourless and odourless gas $\left(C{O}_2\right)$ indicates the presence of $C{O}_3^{2-}$
For $S^{2-}$:
$H_{2}S$ is liberated which has a rotten egg like smell.
For $N{O}_3^{-}:$
When a freshly prepared saturated solution of iron (II) sulphate is
added to nitrate solution and then concentrated $H_{2}S{O}_4$ is added
slowly from side of the test tube, a brown ring is obtained at the
junction of two layers
For $C{l}^{-}$
On treatment with warm conc. $H_{2}S{O}_4$, colourless pungent smelling gas $HCl$ is evolved
Option (a) is correct.