Question about estimating entropy?

In chemistry, we learned that if, for a certain reaction, the amount of gases is higher in the products than the reagents (for example H2O2 ---> H2O + 1/2 O2; only O2 is a gas, so the amount of gas increased during the reaction), it means the total entropy of the system increased. Does that apply to liquids and solids too? I mean, if after a reaction between two solids, you get one solid and one liquid as products, does that also mean that the entropy increased, or does it only apply to gases ?

1 Answer

  • Anonymous
    6 years ago
    Best Answer

    It applies to all states of matter;

    As a rule of thumb you can say that the system is at its most disordered (entropy level is the highest) on the side of the reaction that contains the most moles of a substance AS LONG AS all of your reagents are in the same state.

    So if you had two moles of a liquid on the LHS and three moles of liquid on the RHS then you can say entropy is increasing. However if you had a mixture of states e.g one mole of liquid and one mole of solid on the LHS and two moles of liquid on the RHS, estimating the entropy change would be risky, better to do a calculation to be sure.

    But in general - side with the most moles in total is the most disordered

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