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Entropy and Free Energy

Entropy and Free Energy. 19.3. After reading Section 19.3, you should know:. What entropy and free energy are How to determine whether the entrophy is increasing or decreasing based on a chemical equation How to determine whether a reaction will be spontaneous or not.

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Entropy and Free Energy

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  1. Entropy and Free Energy 19.3

  2. After reading Section 19.3, you should know: • What entropy and free energy are • How to determine whether the entrophy is increasing or decreasing based on a chemical equation • How to determine whether a reaction will be spontaneous or not.

  3. Free Energy – the amount of energy available to do work • Energy that can be obtained by a reaction only if the reaction actually (not theoretically) occurs

  4. Spontaneous or Nonspontaneous? • Spontaneous reactions - reactions that occur naturally • release free energy • favor the formation of products H2CO3 --> H2O + CO2 *** this reactant will produce more than 99% of the products

  5. Spontaneous or Nonspontaneous? • Nonspontaneous reactions - reactions that do not tend to occur • absorb free energy • do not favor the formation of products • not efficient (use a lot of energy) H2O + CO2 --> H2CO3 *** these reactants will produce less than 1% of the products

  6. Entropy – a quantitative measure of the disorder of a system • Reactions want to be in disorder

  7. Entropy increases when… a change in state occurs (solid --> liquid --> gas) a substance is divided into parts

  8. Entropy increases when… if the number of product molecules is greater than the number of reactant molecules H2O (g) H2(g) + O2(g) when the temp increases

  9. How are Enthalpy, Entropy and Free Energy all related??? • Enthalpy (heat energy) and Entropy (disorder) determine whether a reaction is spontaneous or not • Spontaneous • if reaction produced small amounts of energy with high disorder • Nonspontaneous • if reaction produced large amounts of energy with low disorder

  10. If energy is high and disorder is high OR • If energy is low and disorder is low THEN • Spontaneity will depend on the strength of each

  11. Helpful References • Table 19.1 (pg 554) • Figure 19.20 (pg 555)

  12. After reading Section 19.3, you should know: • What entropy and free energy are • How to determine whether the entrophy is increasing or decreasing based on a chemical equation • How to determine whether a reaction will be spontaneous or not.

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