chem question?

Question

in a particular chemical reaction, delta H=+100kj. when equilibrium has been established, it is found that a significant amount of product has formed, even though there is still some reactants left.

what has happened to entropy as this reaction was taking place?..can u explain how you arrived at that answer, cause im not sure how figure out, though rxn is endo why so much product formed.

Answer 1

You are right to mention the entropy. Processes increase total entropy as they move towards equilibrium.

There are two things to consider. One is the entropy of the surrounds. This favours exothermic reactions, which increase the entropy of the surrounds by exporting heat to them. The other is the entropy of the system itself.

In this case, the reaction happens to some extent even though it is importing heat and thereby reducing the entropy of the surrounds. So it must be generating entropy within the system.

For example, the reaction

N2O4 = 2 NO2

absorbs heat, but increases the entropy of the system (more gas molecules!), so it goes to equilibrium with both reactants and products present.

There is an equation in thermodynamics (the Gibbs equation) which describes the tradeoff between the entropy change within the system, and the effect that its enthalpy change has on the entropy of the surrounds.