In organic chemistry, what is the general formula for alkanes?

• A. CnH2n
• B. CnH2n+1
• C. CnH2n+2
• D. CnH2n-2

Answer: (C)

The general formula for alkanes is expressed as CnH2n+2. Alkanes are saturated hydrocarbons, meaning they contain only single bonds between carbon atoms and are fully saturated with hydrogen atoms. The general formula reflects that for every n number of carbon atoms, there are 2n+2 hydrogen atoms.

In this formula, the "+2" accounts for the two additional hydrogen atoms that are present compared to other types of hydrocarbons like alkenes (which have the general formula CnH2n and contain at least one double bond) or alkynes (which have the formula CnH2n-2 and contain at least one triple bond). Alkanes do not exhibit these multiple bonding scenarios, which is why they have the highest number of hydrogen atoms possible for a given number of carbon atoms. This characteristic also contributes to their classification as saturated hydrocarbons.

This understanding helps distinguish alkanes from other hydrocarbons and illustrates the structural properties that arise from the complete saturation of carbon atoms with hydrogen.