Using the Tables in Appendix 1, calculate \(\Delta H\) for the reaction of the following. (a) \(1.00 \mathrm{~L}\) of \(0.100 \mathrm{M} \mathrm{NaOH}\) with \(1.00 \mathrm{~L}\) of \(0.100 \mathrm{M} \mathrm{HCl}\) (b) \(1.00 \mathrm{~L}\) of \(0.100 \mathrm{M} \mathrm{NaOH}\) with \(1.00 \mathrm{~L}\) of \(0.100 \mathrm{M}\) HF, taking the heat of formation of \(\mathrm{HF}(a q)\) to be \(-320.1 \mathrm{~kJ} / \mathrm{mol}\)

Chemical thermodynamics is the subfield of thermodynamics that deals with the study of energy transformations involved in chemical reactions. It involves the principles of heat, work, and internal energy as they are relevant to chemical processes. In this context, the key concept to understand is the enthalpy change, which is a measure of heat change at constant pressure during a chemical reaction.

Researchers often use the laws of thermodynamics to predict the feasibility and spontaneity of chemical reactions, as well as energy exchanges with the surroundings. In a classroom or homework setting, focusing on enthalpy changes offers students a tangible way to connect the abstract concepts of energy and reactions with real, measurable quantities. Moreover, this thermodynamic value is crucial for engineers and scientists when designing systems and processes that optimize energy use and consider environmental impact.

The enthalpy of reaction, denoted as \( \Delta H \) for a given reaction, is essential in understanding how much heat is released or absorbed. It's a central idea in chemical thermodynamics and represents the total heat content of a system. A negative \( \Delta H \) value indicates an exothermic reaction, releasing heat to the surroundings, while a positive value signifies an endothermic reaction, which absorbs heat.

When students calculate enthalpy changes, it’s crucial for them to refer to published tables that list standard enthalpies of formation. These tables allow them to find the change in enthalpy per mole for reactants and products. In the exercise given, for instance, the formation of water and the corresponding \( \Delta H \) is a key step in calculating the total enthalpy change for the reactions involving NaOH with HCl and HF respectively. Simplifying complex tasks, like summing enthalpies, into manageable steps greatly aids in comprehension.

Stoichiometry is the mathematical relationship between the quantities of reactants and products in a chemical reaction. It is fundamentally based on the conservation of mass and the principle that elements are neither created nor destroyed in chemical reactions, but rather rearranged. It involves calculations that rely on the mole concept, balancing equations, and using molar ratios.

To elucidate this concept further, consider the balanced chemical equations in the exercise provided. We see that for every mole of NaOH reacting, there’s a corresponding mole of HCl or HF required due to the one-to-one mole ratio as indicated in the balanced chemical equations. The students’ ability to calculate the moles of reactants is essential in determining the associated enthalpy changes, thus tying stoichiometry directly to the calculation of enthalpy changes. Learning to navigate stoichiometric calculations is critical for students as it serves as the foundation for quantitative analysis in chemistry.