$CO_2$ and $SO_2$ gases can be distinguished by using:

Which of the following can act as both a reducing and an oxidising agent?

Which of the following combinations does not evolve $Cl_2$ gas?

Metal sulphate $(A) \xrightarrow{\text{Heat}}$ Oxide $(B) +$ Gas $(C) +$ Gas $(D) \xrightarrow{Cr_2O_7^{2-} / H^{+}}$ Green solution $\xrightarrow[\text{Excess}]{Na_2O_2}$ Yellow solution $(E)$. Compound $A, B, C, D$ and $E$ are respectively:

The sodium salt of an organic acid $'X'$ produces effervescence with conc. $H_2SO_4$. $'X'$ reacts with an acidified aqueous $CaCl_2$ solution to give a white precipitate which decolourises an acidic solution of $KMnO_4$. $'X'$ is:

Oxalic acid when treated with potassium permanganate in the presence of an acid,produces