Download - Termodinamika Kimia (Part III)
TermodinamikaKimia (Part III)
TRIANNISA RAHMAWATI, S.PD., M.SI.
Beberapa Topik Termodinamika
01. Menjelaskan
Hukum Permana
Termodinamika
02. Menerapkan
perubahan energi
dalam dan perubahan
entalpi dalam system
kimia pada berbagai
keadaan
03. Menjelaskan
makna entropi dan
hukum kedua
termodinamika
04. Menjelaskan makna energi
bebas Gibbs dan hubungannya
dengan kespontanan pada proses
fisika dan kimia
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SPONTANEITY OF PHYSICAL AND CHEMICAL CHANGES
Another major concern of thermodynamics
is predicting whether a particular process
can occur under specified conditions to give
predominantly products.
The concept of spontaneity has a very
specific interpretation in thermodynamics.
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“Which would be more stable at the given conditions—the reactants or the products?”
SPONTANEITY
A change for which the collection of products is thermodynamically more stable than the collection of reactants under the given conditions is said to be product-favored, or spontaneous, under those conditions. A change for which the products are thermodynamically less stable than the reactants under the given conditions is described as reactant-favored, or nonspontaneous, under those conditions.Any spontaneous change has a natural direction, like the rusting of a piece of iron, the
burning of a piece of paper, or the melting of ice at room temperature.
THE TWO ASPECTS OF SPONTANEITYMany product-favored reactions are exothermic. For instance, the combustion (burning) reactions of hydrocarbons such as methane and octane are all exothermic and highly product-favored (spontaneous). The enthalpy contents of the products are lower than those of the reactants.
Not all exothermic changes are spontaneous, however, nor are all spontaneous changes exothermic.Disorder of reactants and products, also plays a role indetermining spontaneity.
Proses Eksotermik
Reaksi pembakaranhidrokarbon → spontan
Pembekuan air
Spontan (diawah 0 ºC)
Tidak spontan (diatas 0 ºC)
THE SECOND LAW OF THERMODYNAMICS
The effect of one factor, the enthalpy change, is that spontaneity is favored (but not required) by exothermicity, and nonspontaneity is favored (but not required) by endothermicity.
The Second Law of Thermodynamics is based on our experiences. Some examples illustrate this law in the macroscopic world. When a mirror is dropped, it can shatter. When a drop of food coloring is added to a glass of water, it diffuses until a homogeneously colored solution results.
The reverse of any spontaneous change is nonspontaneous, because if it did occur, the universe would tend toward a state of greater order.
ENTROPY (S)• The thermodynamic state function entropy, S, is a measure of the disorder of the
system.• The greater the disorder of a system, the higher is its entropy. For any substance,
the particles are more highly ordered in the solid state than in the liquid state.
THIRD LAW OF THERMODYNAMICS
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As the temperature of a substance increases, the particles vibrate more vigorously, sothe entropy increases.The standard entropy change, S0, of a reaction can be determined from the absolute entropies of reactants and products.
Factors that Change Entropy
1. Phase changes
2. Temperature changes
3. Volume changes
4. Mixing of substances
5. Increasing the number of particle
6. Changes in the number of gaseous substances
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Latihan Part III81, 83, 84, 86, 87, 89, 90, 91.
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