How much heat in kilojoules is evolved or absorbed in the reaction of 233.0 g of calcium oxide with enough carbon to produce calcium carbide? Is the process exothermic or endothermic? CaO(s) + 3 C(s) → CaC2(s) + CO(g) ΔH° = 464.6 kJ

Verified step by step guidance

1. Identify the given chemical reaction: \( \text{CaO(s) + 3 C(s) \rightarrow CaC_2(s) + CO(g)} \) with \( \Delta H^\circ = 464.6 \text{ kJ} \).
2. Determine the molar mass of calcium oxide (CaO) using the periodic table: \( \text{Ca} = 40.08 \text{ g/mol} \) and \( \text{O} = 16.00 \text{ g/mol} \).
3. Calculate the number of moles of CaO in 233.0 g using the formula: \( \text{moles of CaO} = \frac{\text{mass of CaO}}{\text{molar mass of CaO}} \).
4. Use the stoichiometry of the reaction to relate the moles of CaO to the enthalpy change: \( \Delta H^\circ \) is given per mole of reaction as written.
5. Determine the total heat evolved or absorbed by multiplying the moles of CaO by \( \Delta H^\circ \), and conclude whether the process is exothermic (releases heat) or endothermic (absorbs heat) based on the sign of \( \Delta H^\circ \).

Key Concepts

Enthalpy Change (ΔH)

Enthalpy change, represented as ΔH, is the heat content change of a system at constant pressure during a chemical reaction. A positive ΔH indicates that heat is absorbed (endothermic reaction), while a negative ΔH indicates that heat is released (exothermic reaction). In this question, the given ΔH° of 464.6 kJ signifies that the reaction absorbs heat, making it endothermic.

Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions based on the balanced chemical equation. It allows us to determine the amount of heat evolved or absorbed per mole of reactants or products. In this case, we need to use the molar mass of calcium oxide and the stoichiometric coefficients from the balanced equation to find the total heat change for 233.0 g of CaO.

Exothermic vs. Endothermic Reactions

Exothermic reactions release heat to the surroundings, resulting in a temperature increase, while endothermic reactions absorb heat, leading to a temperature decrease. The classification of a reaction as exothermic or endothermic is crucial for understanding energy changes. In the provided reaction, since ΔH° is positive, it indicates that the reaction is endothermic, meaning it requires heat input to proceed.