What are homologous series of carbon compounds ? Write the molecular formula of two consecuative members of homologous series of aldehydes. State which part of these compounds determines their (i) physical and (ii) chemical properties.

Explanation

Homologous series. A series of carbon compounds in which the same functional group substitutes for hydrogen on a carbon chain is called a homologous series. There is a difference of `-CH_(2)` in the molecular formulae of two nearest compounds of a homologous series. Each such series has same general molecular formula and has a general scientific name. There is a difference of `14 mu` ( unified mass) in the molecular masses of two nearest compounds of a series.
Members of homologous seris of aldehydes `:`
H - CHO Methanal
`CH_(3) - CHO` Ethanal
`C_(2)H_(5) -CHO` Propanal
(i) The carbon-chain attached to aldehyde group , i.e., `( H-, CH_(3)- , C_(2)H_(5))` determine the physical properties.
(ii) The functional group attached to all aldehydes ( -CHO) determines the chemical properties.