A solution containing a group-IV cation gives a precipitate on passing H₂S. A solution of this precipitate in dil.HCl produces a white precipitate with NaOH solution and bluish-white precipitate with basic potassium ferrocyanide. The cation is :

Sodium salt of an organic acid ‘X’ produces effervescence with conc. H₂SO₄. ‘X’ reacts with the acidified aqueous CaCl₂ solution to give a white precipitate which decolourises acidic solution of KMnO₄. ‘X’ is :

Sodium extract is heated with concentrated HNO₃ before testing for halogens because :

Which of the following reagents may be used to distinguish between phenol and benzoic acid ?