Final answer:
Without specific standard enthalpy of formation values or additional data, the enthalpy change (ΔH) in kilojoules per mole for the reaction H2C=CH2(g) + H2(g) → H3C−CH3(g) cannot be calculated from the information provided.
Step-by-step explanation:
The question is asking for the enthalpy change (ΔH) expressed in kilojoules per mole for the reaction where ethylene (H2C=CH2) reacts with hydrogen gas (H2) to form ethane (H3C-CH3). To find the enthalpy change for the reaction, we would typically look up the standard enthalpy of formation values for each compound and apply Hess's Law. Unfortunately, the question does not provide the necessary thermochemical data to calculate ΔH.
We know from Chemistry principles that the reaction is an example of hydrogenation, where an alkene is converted into an alkane. The process typically exudes heat and thus, the ΔH is expected to be negative, signifying an exothermic process.