Calcium hydroxide, which reacts with carbon dioxide to form calcium carbonate, was used by the ancient Romans as mortar in stone structures. The reaction for this process is: What is the enthalpy change if 3.8 mol of calcium carbonate is formed?

Question

Calcium hydroxide, which reacts with carbon dioxide to form calcium carbonate, was used by the ancient Romans as mortar in stone structures. The reaction for this process is:  What is the enthalpy change if 3.8 mol of calcium carbonate is formed?

Quizplus · Accepted Answer

The balanced chemical equation for the reaction is:
Ca(OH)2 + CO2 → CaCO3 + H2O
The reaction coefficient for CaCO3 is 1, meaning that for every mole of CaCO3 formed, there is an enthalpy change of ΔH = -(-635.5 kJ/mol) = 635.5 kJ/mol. Therefore, for 3.8 mol of CaCO3 formed, the enthalpy change is:
ΔH = 3.8 mol × 635.5 kJ/mol = 2417.9 kJ ≈ 260 kJ (rounded to the nearest integer)
The negative sign indicates that the reaction is exothermic, meaning that heat is released during the reaction. The correct answer is therefore D.

Calcium Hydroxide, Which Reacts with Carbon Dioxide to Form Calcium