When a solution of mixture having two inorganic salts was treated with freshly prepared ferrous sulphate in acidic medium, a dark brown ring was formed whereas on treatment with neutral $$\mathrm{FeCl}_{3}$$, it gave deep red colour which disppeared on boiling and a brown red ppt was formed. The mixture contains :

In Carius tube, an organic compound '$$\mathrm{X}$$' is treated with sodium peroxide to form a mineral acid 'Y'.

The solution of $$\mathrm{BaCl}_{2}$$ is added to '$$\mathrm{Y}$$' to form a precipitate 'Z'. 'Z' is used for the quantitative estimation of an extra element. '$$\mathrm{X}$$' could be

Given below are two statements:

Statement I : Aqueous solution of K$$_2$$Cr$$_2$$O$$_7$$ is preferred as a primary standard in volumetric analysis over Na$$_2$$Cr$$_2$$O$$_7$$ aqueous solution.

Statement II : K$$_2$$Cr$$_2$$O$$_7$$ has a higher solubility in water than Na$$_2$$Cr$$_2$$O$$_7$$.

In the light of the above statements, choose the correct answer from the options given below:

A compound '$$\mathrm{X}$$' when treated with phthalic anhydride in presence of concentrated $$\mathrm{H}_{2} \mathrm{SO}_{4}$$ yields '$$\mathrm{Y}$$'. '$$\mathrm{Y}$$' is used as an acid/base indicator. '$$\mathrm{X}$$' and '$$\mathrm{Y}$$' are respectively