What is the general formula of alkanes ? Identify the alkanes from the following:
`CH_(4),C_(2)H_(2),C_(2)H_(6),C_(3)H_(6),C_(3)H_(8)`

Explanation

The general formula of alkanes is `CnH_(2n+2)` whsere n is the number of carbon atoms in one molecule of the alkane. Out of the above given hydrocarbons `CH_(4),C_(2)H_(6) and C_(3)H_(8)` are alkanes (because they correspond to the general formula `C_(n)H_(2n+2)` with n=1 ,n=2 and n=3, respecitivley) .(please note thet in an alknae molecule the nu,ber of hydrogen atoms is 2 more than double the number of carbon atoms.)
A Golden Rule . We are now going to tell you a golden rule which will help you to know at once wheter the given hydrocarbon is an alkane an alknee or an alkyne . It is like this : Look at the formula of the given hydrocarbon and compare the number of hydrogen atoms with the number of carbon atoms present in it:
(i) If the number of htydrogen atoms is 2 more than double the number of carbon atoms , then it will be an alkane.
(ii) If the number of hydrogen atoms is exactly equal to double the number of carbon atoms , then it will be an alkene
(iii) And if the number of hydrogen atoms is ''2 less'' than double the number of carbon atoms , then it will be an alkyne.