Which of the following is the second member of the alkane series?

The second member of the alkane series is ethane. Alkanes are hydrocarbons that follow the general formula CₙH₂ₙ₊₂, where "n" is the number of carbon atoms. The first member of the alkane series is methane (C₁H₄), which has one carbon atom.

When "n" equals 2, you have ethane, which is C₂H₆, containing two carbon atoms and six hydrogen atoms. This matches the alkane formula, confirming that ethane is indeed the second member of the series after methane.

The other choices—ethanol, butane, and propane—do not fit the criteria for the second member. Ethanol is an alcohol, not an alkane. Butane is the fourth member of the alkane series (C₄H₁₀), and propane is the third member (C₃H₈). Thus, ethane is correctly identified as the second alkane.