Q. An unknown compound A has a molecular formula $ {{C}_{4}}{{H}_{6}}, $ when A is treated with an excess of $ B{{r}_{2}}, $ a new substance B with formula $ {{C}_{4}}{{H}_{6}}B{{r}_{4}} $ is formed. A forms a white precipitate with ammoniacal silver nitrate solution. A may be
AMUAMU 1998
Solution: