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19.6 Gibbs Free Energy
Both were taken to be 25 degrees.
We assigned a zero to the standard enthalpy of formation for an element in its standard state.
The absolute values of enthalpy can't be determined.
The crystal's entropy is zero.
To arrange its components.
The values of standard entropies are listed in Table 19.2.
There is a more complete list in Appendix IIB.
The standard joules per mole per kelvin are listed in units.
The mole in the denominator is required components.
It depends on how much the substance is.
The standard molar entropy of any substance is the energy dispersed into one mole of that substance at 25 degC, which depends on the number of places to put energy within the substance.
The entropy of a gas is greater than that of a liquid, which is in turn greater than the entropy of a solid.
The trends can be seen in the values of standard entropies.
Gaseous water has more ways to arrange its components, which results in greater energy dispersal at 25 degC.
The scope of the book does not include a complete explanation of why entropy increases with increasing mass.
Light and heavy atoms have different energy states associated with their motion.
The closer the energy states are, the greater the dispersal of energy at a given temperature.
Only elements in the same state are affected by this trend.
Solid forms of carbon are included in the allotropes of carbon.
The atoms in diamond are constrained by chemical bonds.
The atoms bond in sheets, but the sheets have freedom to slide past each other.
The less constrained structure of graphite results in more places to put energy.
For a given state of matter, the entropy increases with complexity.
Ar has a bigger mass than NO, yet it has a smaller mass.
Molecules have more places to put energy than atoms.
The only form of energy that can be taken is the motion of the atoms.
In a gaseous sample of NO, energy can be used in a variety of ways.
For a given state, the molecule has a greater entropy than the free atoms.
The energy can be contained in motion.
The more complex the molecule, the more it has in common with simpler ones.
The greater complexity of C2H4 results in a greater molar entropy in these two substances.
The increasing complexity as we move down the list results in more places to put energy.
The increase in solution in its standard state is usually caused by the dissolution of a solid.
Consider the standard entropies of solid and aqueous concentrations of 1 M.
When solid potassium chlorate is dissolved in water, the energy that was concentrated in the crystal is dispersed throughout the solution.
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