Final answer:
In the reaction of ethene with hydrogen gas, ethane is formed through the breaking of a C=C double bond in ethene, thus the correct answer is c. Ethane.
Step-by-step explanation:
When ethene (C₂H₄) reacts with hydrogen gas (H₂), a chemical reaction known as hydrogenation occurs. During this reaction, the C=C double bond in ethene is broken and each carbon atom forms a new bond with a hydrogen atom, resulting in the formation of ethane (C₂H₆).
The balanced chemical equation for this hydrogenation reaction is: C₂H₄(g) + H₂(g) → C₂H₆(g). Therefore, the correct answer to the reaction formula [R] + H₂ for the student's question is c. Ethane. This type of reaction is an example of an alkane being synthesized from an alkene by the addition of hydrogen, commonly known as a reduction reaction in organic chemistry.