Which of the following is the general formula for the homologous series that includes $\mathrm{ethene}$?

• A. $C_n{H}_{2n+2}$
• B. $C_n{H}_{2n-2}$
• C. $C_n{H}_{2n}$
• D. $C_n{H}_n$

Answer: (C)

Verified step by step guidance

1. Identify the compound ethene and write its molecular formula. Ethene is an alkene with two carbon atoms and a double bond, so its formula is \(C_2H_4\).
2. Recall the general formulas for common homologous series: alkanes have \(C_nH_{2n+2}\), alkenes have \(C_nH_{2n}\), alkynes have \(C_nH_{2n-2}\), and so on.
3. Compare the molecular formula of ethene (\(C_2H_4\)) with these general formulas to see which one fits. Substitute \(n=2\) into each formula and check if the hydrogen count matches 4.
4. Since ethene has a double bond, it belongs to the alkene series, which has the general formula \(C_nH_{2n}\).
5. Conclude that the homologous series including ethene is the alkenes, represented by the general formula \(C_nH_{2n}\).