Question
How will you distinguish between dilute $H_2SO_4$ and conc. $H_2SO_4 ?$
✓
Answer
Difference between dilute $H_2SO_4$ and Conc. $H_2SO_4$
| .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. $BaCl _2+ H _2 SO _4 \longrightarrow BaSO _4 \downarrow+2 HCl$ |
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. $Cu +2 H _2 SO _4 \longrightarrow CuSO _4+2 H _2 O + SO _2$ $SO_2$gas turns $K _2 Cr _2 O _7$ 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. $Pb \left( NO _3\right)_2+ H _2 SO _4 \longrightarrow PbSO _4 \downarrow+2 HNO _3$ |
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. $NaCl + H _2 SO _4 \longrightarrow NaHSO _4+ HCl$ |
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