On what conditions does a spontaneous reaction become spontaneous?

Answer 1

For some non-spontaneous reactions, you can change the temperature. For other non-spontaneous reactions, there is nothing you can do to make it spontaneous. Nature favors reactions that increase a system's entropy (disorder) and nature favors reactions that are exothermic (they release enthalpy). Any reaction that does both of these things is spontaneous at all temperatures. Any reaction that does neither of these things is never spontaneous. As far as this question is concerned, the interesting reactions are endothermic reactions that increase entropy and exothermic reactions that decrease entropy. Whether these reactions are spontaneous depends on the temperature. The first variety (endothermic, increase entropy) will be spontaneous at high temperatures; the second (exothermic, decrease entropy) will be spontaneous at low temperatures. To find the temperature at which a reaction becomes spontaneous, one may apply the Gibbs equation: DG = DH - TDS where capital Ds stand for the Greek capital delta.

Answer 2

An enzyme does not change a nonspontaneous reaction into a spontaneous one. A nonspontaneous reaction needs an input of energy where as a spontaneous one does not. Example: an old car rusting over time is a slow spontaneous reaction. An example of a nonspontaneous reaction: water flowing uphill. This action cannot accrue unless input of energy is there, such as a machine that pumps the water against gravity.

Answer 3

If deltaH and deltaS are both negative