(a) Test tube contains a brown liquid in it. The colour of the liquid remains the same when methane is passed through it but it disappears when ethene is passed. Suggest the name of the liquid brown in colour. Give the chemical equaiton involved.
(b) the formula of an ester is `C_(3)H_(7)COOC_(2)H_(5)`. Write the formulae of the acid and alcohol from which the ester is prepared.

Explanation

(a). The brown liquid seems to be bromine dissovled in water. Methane `(CH_(4))` is a saturated hydrocarbon and does not react with bromine. Ethene `(C_(2)H_(4))` being unsaturated in nature, decolourises bromine and its colour therefore,disappears.
`underset("Ethene")(CH_(2))=CH_(2)+underset(("Brown"))(Br_(2)(aq))tounderset("1,2-Dibromoethane (colourless)")(underset(Br)underset(|)(CH_(2))-underset(Br)underset(|)(CH_(2))`
(b) In an ester, the left side in the molecular formula containing `C_(3)H_(7)CO` is derived from the acid while the right side having `OC_(2)H_(5)` is from the alcohol. this means that the aid and alcohol participating in the ester are `C_(3)H_(7)COOH and C_(2)H_(5)OH` respectively.the formation of ester may be shown as follows:
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