For an exothermic reaction, ΔH is:

Entropy of the universe in a spontaneous process:

Gibbs free energy change for a spontaneous process at constant T and P is:

Hess's law is a consequence of:

Standard enthalpy of formation of an element in its standard state is:

Work done in free expansion of an ideal gas is:

The internal energy change for one mole of monoatomic ideal gas heated by 1 K is:

In an adiabatic process:

Bond dissociation enthalpy is always:

For an isothermal reversible expansion of ideal gas:

Cp − Cv for one mole of ideal gas equals:

The enthalpy of combustion is always:

Third law of thermodynamics states that entropy of a perfect crystal at 0 K is:

In an endothermic reaction:

The efficiency of a Carnot engine operating between 500 K and 300 K is:

Enthalpy change at constant pressure equals:

Kirchhoff's equation relates ΔH at two temperatures using:

For an ideal gas in isothermal expansion, ΔH is:

Calorimetry measures:

A process is spontaneous at all temperatures if: