245) Which of the following gives black precipitate when H₂S gas is passed through its solution?

246) A salt gives violet vapours when treated with conc. H₂SO₄. It contains:

247) Which compound is soluble in NH₄OH?

248) Ozone when reacts with potassium iodide solution liberates certain product, which turns starch paper blue. The liberated substance is:

249) When KBr is treated with conc. H₂SO₄, a reddish brown gas is evolved. The evolved gas is: