Physical Chemistry & Thermochemistry
This is a collection of problem sets, lecture notes, articles, and labs for physical chemistry, thermochemistry, and thermodynamics. Laws of Thermochemistry Thermochemical equations are just like other balanced equations except they also specify the heat flow for the reaction. The heat flow is listed to the right of the equation using the symbol ΔH. The most common units are kilojoules, kJ. Here are two thermochemical equations: H2 (g) + ½ O2 (g) → H2O (l); ΔH = -285.8 kJ HgO (s) → Hg (l) + ½ O2 (g); ΔH = +90.7 kJ When you write thermochemical equations, be sure to keep the following points in mind: Coefficients refer to the number of moles. Thus, for the first equation, -282.8 kJ is the ΔH when 1 mol of H2O (l) is formed from 1 mol H2 (g) and ½ mol O2. Enthalpy changes for a phase change, so the enthalpy of a substance depends on whether is it is a solid, liquid, or gas. Be sure to specify the phase of the reactants and products using (s), (l), or (g) and be sure to look up the corre...
