What is the general formula for alkenes?

The general formula for alkenes is CnH2n.

Alkenes are a type of hydrocarbon, which means they are made up of hydrogen and carbon atoms. The 'n' in the formula represents the number of carbon atoms in the molecule. For alkenes, the number of hydrogen atoms is always double the number of carbon atoms, hence the formula CnH2n.

This formula is a result of the fact that alkenes are unsaturated hydrocarbons. This means they contain a carbon-carbon double bond, which reduces the number of hydrogen atoms that can be attached to the carbon atoms. For example, ethene, the simplest alkene, has two carbon atoms and four hydrogen atoms, fitting the formula CnH2n.

The presence of the double bond also gives alkenes their characteristic chemical properties, such as the ability to undergo addition reactions. This is because the double bond is relatively reactive, allowing other atoms or groups of atoms to add across it.

In summary, the general formula CnH2n is a simple way to represent the relationship between the number of carbon and hydrogen atoms in any alkene molecule. It reflects the fact that alkenes are unsaturated hydrocarbons with a carbon-carbon double bond.