Hydrocarbons with the general formula of CₓH₂ₓ₊₂ is for alkanes. These are hydrocarbons that are bonded using single bonds. For example, alkane has the formula of C₂H₆. This is because n=2 and 2(2)+2 = 6. The other general formula, CₓHₓ is for alkenes. These are hydrocarbons that are bonded using double bonds. For example, ethene is C₂H₂.