Final answer:
To determine if the reaction involving 5.00 mol of CO₂ and MgO is endothermic or exothermic, the specific reaction and its associated enthalpy change (ΔH) are needed. Endothermic reactions absorb heat (positive ΔH), while exothermic reactions release heat (negative ΔH). Without specific details, the direct answer to this question cannot be provided.
Step-by-step explanation:
The question asks about the enthalpy change (ΔH) when 5.00 mol of CO₂ reacts with excess MgO. To answer this question, we would need the specific reaction between CO₂ and MgO including its ΔH value. However, based on the provided examples, we can infer general knowledge about thermochemistry.
An endothermic reaction is one that absorbs heat from its surroundings, which is indicated by a positive ΔH value. For example, the decomposition of calcium carbonate (CaCO3) into calcium oxide (CaO) and CO₂ absorbs 177.8 kJ of heat per mole, and thus this reaction is endothermic with ΔH = +177.8 kJ.
On the other hand, an exothermic reaction releases heat into the surroundings and has a negative ΔH value. For example, the combustion of methane (CH4) releasing 213 kcal (or 890.4 kJ) of heat energy is an exothermic process.
Without the specific reaction details for CO₂ and MgO, the direct answer to the student's question cannot be determined. More information about the specific reaction and its enthalpy change would be necessary to conclude whether the reaction is exothermic or endothermic.