Thermochemistry.

Enthalpy, symbol H means heat content.

Cannot measure absolute value of enthalpy of system but can measure enthalpy change (∆H).

∆Hrxn = total enthalpy of products – total enthalpy of reactants

= ∑ Hproducts - ∑ Hreactants

Exothermic reactions : ∆Hrxn = -ve because ∆Hproducts < ∆Hreactants

Endothermic reactions : ∆Hrxn = +ve because ∆Hproducts > ∆Hreactants

Calorimetry: experimental technique to measure ∆Hrxn.

Molar heat capacity: energy required to raise the temperature of 1 mole of the substance by one Kelvin.

Specific heat capacity: energy required to raise the temperature of 1 gram of the substance by one Kelvin, eg specific heat capacity of water is 4.2 J K^-1 g^-1.

∆H = mc ∆T where c = specific heat capacity, m= mass of solution, ∆T = change in temp.