energy + equilibrium

internal energy (U)

• not measurable

• can measure change of internal energies

a,b,c,d create new small levels of MO in LUMO-HOMO theory

enthalpy change

• ΔH is -ve = exo (release)

• ΔH is +ve = ende (absorb)

work done

• by system, pΔV = +ve

• on system, pΔV = -ve

• work (W) closely related to energy

  • W = F x d

conservation of energy

• oral energy of isolated system cannot change (1st law of thermodynamics)

  • → energy can change its form

• ΔH accompanying chemical reaction is independent of pathway between initial and final states (Hess’s law)

why do chemical reactions occur

• energetically feasible reaction at particular temp may not take place at observable rate

• NOT energetically feasible = not take place

• depends on Ea

• catalyst (+/-)

  • new alternative pathway

  • may lower Ea and speed up reaction without consumption

  • BUT no affect to overall energy change in reaction

Arrhenius equation

equilibrium

• conc of R and P remain constant

• forward rate = reverse rate

  • no net changes in conc of R and P

• dynamic equilibrium

Factors effecting eq

• position of eq

• Kc magnitude

• Rate at which eq achieved

applications on eq