1
2
3 3
4 It is obvious that also total energy of the system and its surroundings is constant.
5 U – molar, u – total.
6 6
7
8
9
10 Again, quantities for the whole system will be defined the same way but using
lower case letters.
Internal pressure characterizes molecular interactions leading to an increase in internal energy of the system, depending on its volume.
For rarefied gases, more particularly for the perfect gas internal pressure is equal to nil.
Derivation of the formula for Cp-Cv one can finf in a textbook.
11 CP may be therefore developed in similar power series like CV to express its
dependence on temperature. Assumption Cp=const. is always a simplification.
12
13 Last transformation is obtained using Clapeyron equation once more.
For the time being let’s assume the ratio CP/CV=7/5 for diatomic molecule gases and 5/3 for monoatomic ones.
Explanation will come later.
14 14 The last column shows the coefficient of the equation of reversible adiabatic
process (Poisson’s equation).
15 15 The higher the exponent X, the steeper is the curve on the P-V plane (from
horizontal – isobaric), through hyperboles to vertical straight line (isovolumic).
16 Politrope pVx=const. Its type and shape depends on the value of exponent x.
17 17 For liquid phase reactions, not to say the solid state reactions, differences
between enthalpy of reaction and internal energy of reaction are much smaller.
18 Please, devote some attention to the diagram shown. Similar approach will enable
us to solve many problems.
Strictly speaking, the scheme does not represent a cycle (it is a direct process and a bypass, or detour, both leading, though, from the same inititial to the same final state). What is a cycle? Try to define.
It is assumed here that T2>T1, but it works perfectly also for T1>T2.
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