What is the general chemical formula for alkanes and what does it indicate about their hydrogen content?

• A. CnH2n+2; alkanes are saturated hydrocarbons with the maximum number of hydrogens and only single bonds between carbon atoms.
• B. CnH2n; alkanes are unsaturated hydrocarbons with double bonds.
• C. CnH2n+4; alkanes have extra hydrogens.
• D. CnH2n-2; cyclic alkanes.

Answer: (A)

Alkanes are saturated hydrocarbons, so all carbon–carbon bonds are single bonds and no rings or multiple bonds are present. Each carbon atom forms four bonds, and the hydrogens fill the remaining valence positions, giving the hydrogen count as H = 2n + 2 for n carbon atoms. This pattern is seen in examples like methane (CH4), ethane (C2H6), and propane (C3H8). The higher hydrogen count reflects the maximum number of hydrogens possible for that carbon skeleton; if a double bond or ring were present, there would be fewer hydrogens, which is why the other formulas don’t fit for alkanes.