The decomposition of sodium bicarbonate (baking soda), NaHCO₃(s), into Na₂CO₃(s), H₂O(l), and CO₂(g) at constant pressure requires the addition of 85 kJ of heat per two moles of NaHCO₃. (a) Write a balanced thermochemical equation for the reaction.

Verified step by step guidance

1. Identify the reactants and products in the decomposition reaction: NaHCO3(s) decomposes into Na2CO3(s), H2O(l), and CO2(g).
2. Write the unbalanced chemical equation for the decomposition: NaHCO3(s) → Na2CO3(s) + H2O(l) + CO2(g).
3. Balance the chemical equation by ensuring the number of each type of atom is the same on both sides. For this reaction, you need 2 moles of NaHCO3 to produce 1 mole of Na2CO3, 1 mole of H2O, and 1 mole of CO2. The balanced equation is: 2 NaHCO3(s) → Na2CO3(s) + H2O(l) + CO2(g).
4. Incorporate the thermochemical data into the balanced equation. Since 85 kJ of heat is required for the decomposition of 2 moles of NaHCO3, this energy change is written on the reactant side as it is an endothermic reaction: 2 NaHCO3(s) + 85 kJ → Na2CO3(s) + H2O(l) + CO2(g).
5. Verify that the equation is balanced both in terms of mass and energy, ensuring that the stoichiometry and the thermochemical data are correctly represented.