The decomposition of \(\mathrm{Ca}(\mathrm{OH})_{2}(s)\) into \(\mathrm{CaO}(s)\) and \(\mathrm{H}_{2} \mathrm{O}(g)\) at constant pressure requires the addition of 109 \(\mathrm{kJ}\) of heat per mole of \(\mathrm{Ca}(\mathrm{OH})_{2}\) . (a) Write a balanced thermochemical equation for the reaction. (b) Draw an enthalpy diagram for the reaction.

To write the balanced chemical equation for the decomposition of calcium hydroxide, we need to show that the number of atoms for each element is equal on both sides of the equation: Ca(OH)₂(s) → CaO(s) + H₂O(g) This equation is already balanced since there is one calcium, two oxygen, and two hydrogen atoms on both sides. Step 2. Write the thermochemical equation for the reaction.

We are given that the reaction requires 109 kJ of heat per mole of Ca(OH)₂. The heat added to the reaction is positive because it is an endothermic reaction (the system absorbs energy from its surroundings). The thermochemical equation will include this heat value: Ca(OH)₂(s) + 109 kJ → CaO(s) + H₂O(g) Step 3. Draw an enthalpy diagram for the reaction.

To draw an enthalpy diagram for the reaction, we need to represent the differences in enthalpy (ΔH) between the reactants and products. For an endothermic reaction, the enthalpy of the products is higher than that of the reactants. The diagram will show the reactants on a lower enthalpy level, and the products on a higher enthalpy level with a vertical arrow between them indicating the change in enthalpy (+109 kJ). The enthalpy diagram should look like this: Reactants: Ca(OH)₂(s) | | +109 kJ ↓ Products: CaO(s) + H₂O(g) In conclusion, the thermochemical equation for the decomposition of calcium hydroxide is Ca(OH)₂(s) + 109 kJ → CaO(s) + H₂O(g), and the enthalpy diagram demonstrates that the reaction is endothermic with an enthalpy change of +109 kJ.