Chemistry
Harsh performed the following experiments in the laboratory. State one significant observation made by Harsh when:
(a) he added concentrated sulphuric acid to blue vitriol.
(b) he passed ammonia gas over heated PbO.
(c) sodium hydroxide solution was added to CuSO4 solution by him.
Sulphuric Acid
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Answer
(a) When Harsh added concentrated sulphuric acid to blue vitriol (CuSO4.5H2O), the blue colour crystals lose their blue colour and become white (anhydrous copper sulphate) this is because of loss of water molecules.
(b) When he passed ammonia gas over heated PbO, ammonia reduces heated yellow lead monoxide to greyish metallic lead.
2NH3 + 3PbO ⟶ 3Pb + 3H2O + N2 [g]
(c) On adding sodium hydroxide solution to CuSO4 solution, Harsh obtained a pale blue precipitate of Cu(OH)2 which was insoluble in excess of sodium hydroxide.
CuSO4 + 2NaOH ⟶ Cu(OH)2 + Na2SO4
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