What is the general formula for alkenes?

The general formula for alkenes is CnH2n, where 'n' is the number of carbon atoms in the molecule. Alkenes are hydrocarbons that contain at least one carbon-carbon double bond (C=C). The formula highlights that for every carbon atom in the alkene, there are two hydrogen atoms associated with each pair of carbon atoms involved in the double bond. This results in a decrease in the number of hydrogen atoms compared to alkanes, which follow the formula CnH2n+2, as alkenes have fewer hydrogen atoms due to the presence of the double bond.

The structural presence of a double bond means that the molecule is unsaturated, which is a key characteristic of alkenes. For example, when n = 2 (the simplest alkene, ethene), the formula indicates that there are 4 hydrogen atoms (C2H4). This relationship between the number of carbon and hydrogen atoms confirms the understanding of alkenes as unsaturated hydrocarbons, making CnH2n the correct general formula.