The decomposition of sodium bicarbonate (baking soda), \(\mathrm{NaHCO}_{3}(s)\), into $\mathrm{Na}_{2} \mathrm{CO}_{3}(s), \mathrm{H}_{2} \mathrm{O}(l)\(, and \)\mathrm{CO}_{2}(g)$ at constant pressure requires the addition of \(85 \mathrm{~kJ}\) of heat per two moles of \(\mathrm{NaHCO}_{3} .\) (a) Write a balanced thermochemical equation for the reaction. (b) Draw an enthalpy diagram for the reaction.

: First, write down the balanced chemical equation for the decomposition of sodium bicarbonate: \[\mathrm{2NaHCO}_{3}(s) \rightarrow \mathrm{Na}_{2}\mathrm{CO}_{3}(s) + \mathrm{H}_{2}\mathrm{O}(l) + \mathrm{CO}_{2}(g)\] Now, incorporate the given heat value (85 kJ) for the required constant pressure process. Since heat is required for the reaction, it is an endothermic reaction, thus we'll add the heat term on the left side of the equation: \[\mathrm{2NaHCO}_{3}(s) + 85 \,kJ \rightarrow \mathrm{Na}_{2}\mathrm{CO}_{3}(s) + \mathrm{H}_{2}\mathrm{O}(l) + \mathrm{CO}_{2}(g)\] This is the balanced thermochemical equation for the given reaction.

: An enthalpy diagram represents the changes in enthalpy during a reaction. Since this is an endothermic reaction, the products will have a higher enthalpy than the reactants. Follow these steps to draw the enthalpy diagram: 1. Label the y-axis as enthalpy (H), with an upward direction indicating an increase in enthalpy. 2. On the x-axis, write the reactant species on the left and the product species on the right. 3. Draw an arrow pointing upwards from the level of reactants to the level of products, indicating the change in enthalpy during the reaction. 4. Label the arrow with the amount of heat required for the reaction (85 kJ). The enthalpy diagram should look like this: Reactants: 2NaHCO₃(s) -------->|↑ |↑ 85 kJ |↑ Products: Na₂CO₃(s) + H₂O(l) + CO₂(g) This diagram showcases the endothermic nature of the reaction and the increase in enthalpy from reactants to products with the involvement of 85 kJ of heat.