#Thermodynamics calculator si how to

So if you had to calculate the Gibbs free energy change at, say, 298 K, you can just slot the numbers in:

#Thermodynamics calculator si how to

But you should, of course, know how to calculate this from enthalpy changes of formation. This reaction is actually the combustion of methane, and so we can just take a value of this from a Data Book. On an earlier page in this section, we calculated the entropy change for the reactionīefore you do anything else, convert this to kJ by dividing by 1000. You must remember to change the entropy change value into kJ before you start, otherwise you will get the calculation completely wrong. There is an easy mistake to be made though! You have to remember that the entropy change is calculated in energy units of joules, but ΔG° and ΔH° are both measured in kJ.īecause you are calculating ΔG, your answer will be in kJ mol -1. If you know (or can work out) the enthalpy change for the reaction, and you know (or can work out) the entropy change, and you know the temperature (in kelvin), then it would seem to be really easy to work out ΔG°. This is how standard Gibbs free energy change is calculated: If you have already read the page about how to do this with total entropy changes, you will find a little bit of repetition on this page. This page introduces Gibbs free energy (often just called free energy), and shows how it can be used to predict the feasibility of reactions.