#ENTROPY VS ENTHALPY FREE#

So, since it’s convention to give entropy in joules per kelvin per mole, whenever we work out the entropy change from the gradient of a graph, we need to multiply our answer by one thousand. …which explains why it’s a thousand times smaller. This value is in joules per kelvin per moleīut this value is in kilo joules per kelvin per mole So why are they different? Have we made a mistake? The value we calculated is exactly a thousand times smaller than the data book value. However, this time, when we compare our answer to the data book value, they match up poorly. We find the gradient by drawing a triangle like this, finding the change in y and the change in x, dividing the change in y by the change in x, and evaluating to give this.Īnd so, since the entropy change for the reaction is the negative of the gradient of this line, that means it must be this. The entropy change for this reaction is related to the gradient of this graph by this equation Next, what’s the entropy change for this reaction? The enthalpy change for this reaction is this, because that’s the intercept of this graph.Īnd when we compare our answer to the data book value, they match up well! What’s the enthalpy change for this reaction? So, here’s the graph for the reaction between methane and water. Last time we saw that all graphs of delta g against temperature will have a gradient of this, and an intercept of this. How Are Reversible Reactions Compatible With the Second Law of Thermodynamics?

#ENTROPY VS ENTHALPY FREE#

Calculating Gibbs Free Energy Change for Reverse ReactionsĢ4. Entropy describes the disorder of a system, while enthalpy describes the total heat content of a system. The Limitations of Our Temperature-Finding EquationĢ1. Finding the Temperature Where Reactions Become FeasibleĢ0. Using Graphs to Find Enthalpy and Entropy Changesġ9. Exam Technique: Explaining Feasibilityġ7. Assessing Feasibility – Thermal Decomposition of Calcium Carbonateġ5. Why Do Some Feasible Reactions Not Happen?ġ0. Calculating the Entropy Change of the Surroundingsħ.

Entropy vs enthalpy