In thermodynamics work done by a system on the surroundings during a process is defined as that interaction whose external system could be viewed as the raising of a mass through a distance against gravitational force.

The list of**Thermodynamics Formulas** are given below.

The list of

A number of thermodynamic functions cannot be measured directly. We
need to be able to express these quantities in terms of others that can
be experimentally determined.

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Solved problems based on thermodynamics are given below. ### Solved Examples

**Question 1: **When 100kJ of work done on a closed system during a process, the total energy of the system increases by 55.0kJ. Calculate how much heat is either added or removed from the system?

** Solution: **

In accordance with the principle of energy conservation, a net energy transfer to a system results in an equal increase of internal energy stored in the system. This may be written as

Q = $\Delta$E + W

This equation is usual statement of first law. It says that in any change of state the heat supplied to a system is equsl to the increase of internal energy in the system plus the work done by the system.

Considering the work done on a system as positive

Q + (+100.0) = +55.0

Q = +55.0 - 100.0

Q = -45.0kJ

From the result due to the negative sign 45.0kJ of energy in the form of heat is removed from the system during the process.

**Question 2: **Refrigerant 12 (Freon 12) at 20 psia and 30^{o}F is compressed to 140 psia and 150^{o}F during a compression stroke. For a pound of this refrigerant calculate the work done during compression.

** Solution: **

From the table of thermodynamic properties for refrigerent 12 the original and final specific volumes are 2.0884 and 0.33350 cu ft/lb respectively. For the process

$\frac{140}{20}$ = $\left(\frac{2.0884}{0.33350}\right)^{2}$

7 = (6.262)n and n = 1.0607

The work of compression equals

W = $\frac{P_{2}V_{2} - P_{1}V_{1}}{1-n}$

W = $\frac{144}{1-1.067}$ $\times$ (140 $\times$ 0.3335-20 $\times$ 2.0884)

W = -11,670ft-1b

In accordance with the principle of energy conservation, a net energy transfer to a system results in an equal increase of internal energy stored in the system. This may be written as

Q = $\Delta$E + W

This equation is usual statement of first law. It says that in any change of state the heat supplied to a system is equsl to the increase of internal energy in the system plus the work done by the system.

Considering the work done on a system as positive

Q + (+100.0) = +55.0

Q = +55.0 - 100.0

Q = -45.0kJ

From the result due to the negative sign 45.0kJ of energy in the form of heat is removed from the system during the process.

From the table of thermodynamic properties for refrigerent 12 the original and final specific volumes are 2.0884 and 0.33350 cu ft/lb respectively. For the process

$\frac{140}{20}$ = $\left(\frac{2.0884}{0.33350}\right)^{2}$

7 = (6.262)n and n = 1.0607

The work of compression equals

W = $\frac{P_{2}V_{2} - P_{1}V_{1}}{1-n}$

W = $\frac{144}{1-1.067}$ $\times$ (140 $\times$ 0.3335-20 $\times$ 2.0884)

W = -11,670ft-1b