For a reaction to be spontaneous under standard conditions at all temperatures, the signs of ΔH° and ΔS° must be negative and positive, respectively. <span>Gibbs free energy (G) determines if reaction will proceed
spontaneously, if </span>ΔG is negative, reaction is spontaneous.<span>
ΔG = ΔH - T·ΔS.
ΔG - changes in Gibbs free energy.
ΔH - changes in enthalpy.
ΔS - changes in entropy.
T is temperature in Kelvins.</span>