Consider the following statements regarding the preliminary tests of anions with dilute H ₂ SO ₄ : I. A carbonate salt gives a colourless and odourless gas that turns lime water milky. II. A sulphide salt evolves a gas with a pungent smell of burning sulphur. III. A sulphite salt evolves a gas that turns acidified potassium dichromate paper green. IV. A nitrite salt yields a colourless gas which turns into reddish-br

Step-by-step solution

Statement I is correct: Carbonate salts react with dilute H ₂ SO ₄ to evolve CO ₂ gas, which is colourless, odourless, and turns lime water milky. Statement II is incorrect: Sulphide salts evolve H ₂ S gas, which has a characteristic smell of rotten eggs. The pungent smell of burning sulphur is a characteristic of SO ₂ gas (evolved from sulphites). Statement III is correct: Sulphite salts evolve SO ₂ gas, which is a reducing agent and turns acidified potassium dichromate paper green due to the formation of Cr ³⁺ io