1 : First Law of Thermodynamics:
  • ∆U = q - W
  • The change in internal energy (∆U) of a system is equal to the heat (q) added to the system minus the work (W) done by the system on its surroundings.
2 : Enthalpy (H):
  • H = U + PV
  • Enthalpy is the sum of internal energy and the product of pressure (P) and volume (V).
3 : Standard Enthalpy Change (∆H°):
  • ∆H° = ∑(∆H°f(products)) - ∑(∆H°f(reactants))
  • It represents the change in enthalpy for a chemical reaction at standard conditions. It is related to the standard enthalpies of formation (∆H°f) of products and reactants.
4 : Standard Entropy (S°):
  • S° is the measure of disorder in a system. It is often given in J/(mol•K).
5 : Gibbs Free Energy (∆G):
  • ∆G = ∆H - T∆S
  • Gibbs free energy is a measure of the spontaneity of a process. If ∆G is negative, the process is spontaneous.
6 : Gibbs-Helmholtz Equation:
  • ∆G = ∆H - T∆S
  • ∆G = ∆G° + RT ln(Q)
  • This equation relates the Gibbs free energy change to enthalpy, entropy, temperature (T), and the reaction quotient (Q).
7 : Van’t Hoff Equation:
  • ln(K2/K1) = -(∆H°/R) * (1/T2 - 1/T1)
  • The Van’t Hoff equation relates equilibrium constants (K) to temperature changes (∆T) and the enthalpy change (∆H°).
8 : Second Law of Thermodynamics:

The entropy of an isolated system tends to increase over time, leading to greater disorder and randomness.

9 : Third Law of Thermodynamics:

The entropy of a perfectly crystalline substance at absolute zero temperature is zero.

10 : Entropy Change in an Irreversible Process:
  • ∆S ≥ q/T
  • This equation relates the change in entropy to heat exchange and temperature for an irreversible process.
11 : Clausius-Clapeyron Equation:
  • ln(P2/P1) = (∆Hvap/R) * (1/T1 - 1/T2)
  • This equation relates vapor pressure, enthalpy of vaporization, and temperature.
12 : Relationship between ∆G° and K:
  • ∆G° = -RT ln(K)
  • This equation relates the standard Gibbs free energy change to the equilibrium constant (K).
13 : Work Done in Expansion or Compression of Gases:
  • W = -P∆V
  • For a reversible isothermal process, W = -nRT ln(Vf/Vi)
14 : Relationship between ∆G° and ∆G:

∆G = ∆G° + RT ln(Q)

If ∆G < 0, the reaction is spontaneous.

15 : Hess’s Law:**
  • The enthalpy change for a chemical reaction is independent of the pathway taken from reactants to products