Chem 112 Exam AID Course Pack

02 x 10 33 j 129 x 10 15 j 154 x 10 9 j 6 what is

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: ll they reach the same temperature − This concerns itself with temperature and thermal equilibrium among bodies. First Law of Thermodynamics: − Energy is conserved it can be changed from one form to another, however it can not be created nor destroyed. − ΔU = q + w − ΔU = change in internal energy (J) − q = heat released/absorbed − w = work done on/by the system € € Heat (q): is not a state function and refers to the thermal transfer • If exothermic process heat is departing the system therefore internal energy is decreased (- ΔU ) • If endothermic process heat is deposited into the system therefore the internal energy is € Ethan Newton & Barry Zhang for SOS Winter 2012 27 € € increased (+ ΔU ) Work (w): is the transfer of energy into or out of the system • Work done ON a system transfers energy into the system (+ ΔU ) € • Work done BY the system uses energy to do work on the surroundings (- ΔU ) W = PΔV € Second Law of Thermodynamics: € If a reaction is spontaneous entropy of the universe increases € Calorimetry: Is the measure of heat change. The heat absorbed or released is given by the following equation. q = mcΔT m: mass c: specific heat ΔT : change in temperature Special cases: − Adiabatic: no heat enters of leaves the system (q=0) − Isothermal: constant temperature is maintained ( ΔT =0) Heat: measured in Joules or calories − Endothermic reactions absorb heat energy (+q) € − Exothermic reactions release heat (- q) The second law can be integrated into the zeroth Heat Lost = - (Heat Gained) m1c1 Tf − T1o = m2c 2 Tf − T2 o Enthalpy: €Preformed under constant pressure (1atm). Enthalpy is used to express the heat changes at constant pressure. The change in the enthalpy is equal to the heat absorbed/released. This a state function that depends on the initial and final states but not the path used to get there. Hence ΔH Rxn = H products − H reac tan ts ΔH Rxn = ΔH ° f (products) − ΔH ° f (reactants) − Endothermic: ΔH Rxn is positive ( € € ) ( ) € Ethan Newton & Barry Zhang for SOS Winter 2012 28 − Exothermic: ΔH Rxn is negative − In the standard state the heat of formation is zero (ex: O2) − Additive (Hess’ Law) − If the pressure is not constant then we measure the internal energy in a similar manner €...
View Full Document

Ask a homework question - tutors are online