Two students A and B were asked to carry out one experiment. The smoke released due to the burning of candle should be passed through lime water and anhydrous copper sulphate to prove the release of CO_(2)andH_(2)O respectively due to the burning of the candle. 'A' first passed the gases through lime water and then through copper sulphate whereas 'B' did it the other way round. The Teacher commented that the set up used by 'A' was wrong. What could be the reason for it?

Two students A and B were asked to carry out one experiment. The smoke

1.	Two students A and B were asked to carry out one experiment. The smoke released due to the burning of candle should be passed through lime water and anhydrous copper sulphate to prove the release of CO_(2)andH_(2)O respectively due to the burning of the candle. 'A' first passed the gases through lime water and then through copper sulphate whereas 'B' did it the other way round. The Teacher commented that the set up used by 'A' was wrong. What could be the reason for it?
Answer» Solution :The PRODUCTS of the combusiton of a candle (MIXTURE of hydrocarbons) are `CO_(2)` and water vapoure. `CO_(2)` can be detected by passing it through lime water which TURNS milky. `H_(2)O` can be detected by passing it through anhydrous `CuSO_(4)` which turns blue. After passing it through anhydrous `CuSO_(4)` first, `H_(2)O` is removed and only `CO_(2)` will be passed through lime water. If the process is reversed, then `CO_(2)` will be absorbed in lime water and water vapour gets condensed. Hence colour of anhydrous `CuSO_(4)` remains unchanged.