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Question
How will you distinguish between dilute H2SO4 and conc. H2SO4 ?
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Solution
Difference between dilute H2SO4 and Conc. H2SO4 :
| S.NO. | Dilute Sulphuric acid | Concentrated sulphuric acid |
| 1 | Barium chloride test : Barium chloride is added to dilute sulphuric acid white ppt.s of barium sulphate is formed. The precipitate is insoluble in dil.hydrochlroic acid or nitric acid. \[\ce{BaCl2 + H2SO4 -> BaSO4 v + 2HCl}\] |
Addition to copper : Conc. sulphuric acid is added to copper and heated. Sulphur dioxide, which is colourless gas with the smell of burnt sulphur is evolved. SO2 gas turns K2Cr2O7 paper green. |
| 2 | Lead nitrate test : Lead nitrate is added to dil. sulphuric is acid. White ppt. of lead sulphate is formed. The ppt. is insoluble in dil. Hydrochloric acid or nitric acid. \[\ce{Pb(NO3)2 + H2SO4 -> PbSO4 v + 2HNO3}\] |
Addition of common salt : Common salt is added to conc. sulphuric acid. Hydrogen chloride a colourless pungent smelling acidic gas is evolved. Dense white fumes are seen if a rod dipped in ammonia solution is brought near it. \[\ce{NaCl + H2SO4 -> NaHSO4 + HCl}\] |
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