Which sequence lists alkanes in increasing number of carbon atoms?

Which sequence lists alkanes in increasing number of carbon atoms?

• A. Methane, Ethane, Propane, Butane
• B. Ethane, Methane, Propane, Butane
• C. Propane, Butane, Ethane, Methane
• D. Butane, Propane, Ethane, Methane

Answer: (A)

The concept here is ordering alkanes by how many carbon atoms they have. Alkanes form a homologous series where each step adds one carbon, so the sequence goes from 1 carbon to 2, to 3, to 4, and so on. Methane has 1 carbon, ethane has 2, propane has 3, and butane has 4. Therefore the increasing order by carbon count is methane, then ethane, then propane, then butane. Any sequence that starts with a larger alkane or swaps the order breaks the pattern of increasing carbon atoms.

The concept here is ordering alkanes by how many carbon atoms they have. Alkanes form a homologous series where each step adds one carbon, so the sequence goes from 1 carbon to 2, to 3, to 4, and so on. Methane has 1 carbon, ethane has 2, propane has 3, and butane has 4. Therefore the increasing order by carbon count is methane, then ethane, then propane, then butane. Any sequence that starts with a larger alkane or swaps the order breaks the pattern of increasing carbon atoms.