There are two hydrocarbons having the formula 4H10, and these are known as normal butane and isobutane. The two butanes are isomers. They have the same empirical formula, and hence the same composition, but different physical and chemical properties, because they differ in the arrangement of the atoms in their molecules. normal butane. n butane, is astraight chain?molecule and isobutane isa“ branched chain” molecule. The number of possible isomers increases with increasing molecular weight; the hydrocarbon of large molecular weight have great numbers of isomers.There are two hydrocarbons having the formula C4H10, and these are known as normal butane and isobutane. The two butanes are isomers. They have the same empirical formula, and hence the same composition, but different physical and chemical properties, because they differ in the arrangement of the atoms in their molecules. Normal butane, n￾butane, is a “straight chain” molecule and isobutane is a “branched chain” molecule. The number of possible isomers increases with increasing molecular weight; the hydrocarbon of large molecular weight have great numbers of isomers