Question

X, Y and Z are three crystalline solids which are soluble in water and have a common anion. To help you to identify X, Y and Z, you are provided with the following experimental observations. A reddish-brown gas is obtained when X, Y and Z are separately warmed with concentrated sulphuric acid and copper turnings added to mixture.

Answer 1

We know that the Nitrate ion can be easily identified after heating copper turnings with concentrated sulfuric acid. Brown colour with pungent effervescence is monitored which turns blue litmus red.

Complete answer:
As we know that the copper nitrate also occurs as various five different hydrates where the most common one are the trihydrate and hemipentahydrate. Acetic anhydride in combination with Copper nitrate is an effective reagent for the nitration of different aromatic compounds which are known as the Menke nitration in honor of the Dutch chemist who discovered that metal nitrates are very effective reagents for the process called nitration. The common anion is nitrate $\left( NO_{3}^{-} \right).$ Evolution of reddish brown fumes are indicative of the presence of nitrate (evolution of $NO$ gas) or bromide ions (evolution of $B{{r}_{2}}$ gas). But since fumes are intense by adding copper turnings it confirms the presence of nitrate $\left( NO_{3}^{-} \right).$
Therefore, the common anion between X, Y, Z is $NO_{3}^{-}$

Note:
Remember that the Copper Nitrate is very toxic to the aquatic life and biological diversity of various water bodies. It’s toxicity affects many living entities as well as surfaces of various positions. Copper Nitrate is an inorganic compound that forms a blue crystalline solid. Copper nitrate also occurs as five different hydrates, the most common ones being the hemipentahydrate and trihydrate.