S is calculated by using the following equation:
In the first part of this unit, we presented the first law of thermodynamics, which states energy is conserved during any process. In this section, we are going to talk about the second law of thermodynamics, which involves entropy. Entropy is a quantitative measurement of the degree of disorder in a chemical system. The second law of thermodynamics states that changes within a system favor higher entropy. The third law of thermodynamics states that the entropy of a perfect crysatl at 0K is 0. At any temperature higher than 0K, vibrations within the atoms begin, and disorder results. In your book, there should be a table of standard entropies for most common compounds at 25°C, symbolized S°. For a chemical reaction, the S is calculated by using the following equation:
S = S°(products) - S°(reactants) S for a reaction means that the products have more entropy, thus being more favorable. However, you must also take enthalpy into effect to determine whether a reaction will take place.
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