Which element commonly acts as a catalyst in the hydrogenation of alkenes?

• A. Pt
• B. Cl
• C. Na
• D. O

Answer: (A)

Verified step by step guidance

1. Understand the process of hydrogenation: it is the addition of hydrogen (H\_2) across the double bond of an alkene, converting it into an alkane.
2. Recognize that hydrogenation reactions typically require a catalyst to proceed efficiently at reasonable conditions.
3. Recall that common catalysts for hydrogenation are transition metals that can adsorb hydrogen and the alkene onto their surface, facilitating the reaction.
4. Identify that among the given options, platinum (Pt) is a well-known and widely used catalyst for hydrogenation reactions.
5. Conclude that Pt acts as the catalyst by providing a surface for the reaction to occur, while Cl, Na, and O do not commonly serve this catalytic role in hydrogenation.