Question

The following materials are provided – solutions of cobalt chloride, ammonia, potassium permanganate, lime water, starch-iodide, sodium hydroxide, lead acetate, potassium iodide. Also provided are litmus and filter papers, glowing splinters and glass rods. Using the above how would you distinguish between : 

(a) hydrogen sulphide and nitrogen dioxide gas 

(b) ammonia and carbon dioxide gas 

(c) zinc carbonate and potassium nitrate 

(d) hydrated copper sulphate and anhydrous copper sulphate 

(e) ammonium sulphate and sodium sulphate. 

Answer 1

(a) H₂S gas turns KMnO₄ from pink to colourless and NO₂ liberates violet vapours with KI. 

(b) NH₃ turns red litmus blue and SO₂ turns blue litmus red. 

(c) Lime water turns zinc carbonate milky and no effect on potassium nitrate. 

(d) Hydrated copper sulphate anhydrous copper sulphate. Take some dry CuSO₄ on filter paper. It will be white in colour. anhydrous copper sulphate white in colour. CuSO₄ (white powder) Now keep it in air for some time, it will absorb water vapous from atmosphers, its colour will change to blue. 

(e) Ammonium sulphate and sodium sulphate : When ammonium sulphate is heated with NaOH, gas ammonia is producedwhich turns red litmus blue. But sodium sulphate has no reaction with NaOH.