CHE 31 Lecture Notes - Bond-Dissociation Energy, Hydrofluoric Acid, Thermochemistry
Document Summary
Enthalpy change is the heat change(heat evolved or absorbed at constant pressure). One of the devices to measure enthalpy change is coffee cup calorimeter. 2nh3 h =-92. 2kj is a thermochemical equation (g) (g) H2+ 12o2: find ho for the formation of 2moles of water, find ho for the formation of 2moles of h2, find ho for the formation of 9g of water j. Enthalpy change for a rection remains the same whether it takes place in one step or many steps. Standard state of a substance is the most stable state of the substance at 1atm and 25oc(usually) Standard enthalpy of formation = h0 compound is formed from its elements in their standard state(stable state at 1atm and. 25oc) f , is the enthalpy change when 1 mole of a. Ohf of p4 (s) =0 f (h2)g = 0 f (elements)=0. Ho = ho f (products)- ho f (reactants) Enthalpy of formation of hf(heat formation of hf)
