Cliffs AP Chemistry, 3rd Edition

∆Hreaction= −qwater

gC gC

specific heat of water^418. J^1 cal

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∆H°= ΣH°f products−ΣH°f reactants= qp

where qp= heat flow, constant p

1 calorie = 4.184 Joules

101 Joules = 1 liter ⋅atm

24.14 calories = 1 liter ⋅atm

• law of Dulong and Petit

molar mass ⋅specific heat ≈25 J/mole ⋅°C

• first law of thermodynamics

∆E= q+ w= qp−P∆V= ∆H−P∆V

In any process, the total change in energy of the system, ∆E, is equal to the sum of the

heat absorbed, q, and the work, w, done on the system.

• second law of thermodynamics

∆Suniv= ∆Ssys+ ∆Ssurr> 0 spontaneous

∆Suniv= ∆Ssys+ ∆Ssurr< 0 nonspontaneous

∆Suniv= ∆Ssys+ ∆Ssurr= 0 equilibrium

The entropy of the universe increases in a spontaneous process and remains unchanged in

an equilibrium process.

• third law of thermodynamics

S°= qp/ T

∆S°= ΣS°products−ΣS°reactants

The entropy of a perfect crystalline substance is zero at absolute zero.

• Hess’s law: If reaction (1) has ∆H 1 and reaction (2) has ∆H 2 and reaction (1) +
  reaction (2) = reaction (3), then
  ∆H 3 = ∆H 1 + ∆H 2


• Bond breaking: potential energy (enthalpy) of bond is increased; “strong” bonds →
  “weak” bonds; ∆H > 0.
  Bond forming: potential energy (enthalpy) of bond is decreased; bond distance is de-
  creased; “weak” bonds →“strong” bonds; ∆H< 0.
  ∆H= Σbond energy (reactants) −Σbond energy (products) = total energy input −total
  energy released

Thermochemistry