THE CHANGE OF IDEAL GAS CONDITION BY APPLYING THERMODYNAMICS LA

THE CHANGE OF IDEAL GAS CONDITION BY APPLYING THERMODYNAMICS LAW 

CHAPTER I

INTRODUCTION

Lots of interesting properties of the ideal gas. Although the actual gas with properties exactly like that of an ideal gas does not exist, but pretty good ideal gas is used as the approach of real gas properties in certain conditions. In thermodynamics, the gas that is used as the workpiece is generally all considered as an ideal gas. This is because the properties of an ideal gas differs only slightly from the properties of the real gas. In terms of the notion of an ideal gas (perfect), which is a gas in which the power tie molecules can be ignored. So every gas When power tie molecules in the gas are negligible relatively ideal.

The ideal gas model tends to fail at lower temperatures or higher pressures, when intermolecular forces and molecular size become important. It also fails for most heavy gases, such as many refrigerants,^[1] and for gases with strong intermolecular forces, notably water vapor. At some point of low temperature and high pressure, real gases undergo a phase transition, such as to a liquid or a solid. The model of an ideal gas, however, does not describe or allow phase transitions. These must be modeled by more complex equations of state.

The ideal gas model has been explored in both the Newtonian dynamics (as in "kinetic theory") and in quantum mechanics (as a "gas in a box"). The ideal gas model has also been used to model the behavior of electrons in a metal (in the Drude model and the free electron model), and it is one of the most important models in statistical mechanics.

The ideal gas law is utilized by engineers working with gases because it is simple to use and approximates real gas behavior. Most physical conditions of gases used by man fit the above description. Perhaps the most common use of gas behavior studied by engineers is that of the compression process using ideal gas approximations. Such a compression process may occur at constant temperature (pV = constant), constant volume, or adiabatic (no heat transfer).Whatever the process, the amount of work that results from it depends upon the process, as brought out in the discussion on the First Law of Thermodynamics.

CHAPTER II

DISCUSSION

In thermodynamics, the gas that is used as the workpiece is generally all considered as an ideal gas. This is because the properties of an ideal gas differs only slightly from the properties of a real gas. Gas ideal (perfect) gas which is a power tie molecules can be ignored. So every gas When power tie molecules in the gas are negligible relatively ideal. An ideal gas is a theoretical gas composed of a set of randomly moving, non-interacting point particles. The ideal gas concept is useful because it obeys the ideal gas law, a simplified equation of state, and is amenable to analysis under statistical mechanics.

At normal conditions such as standard temperature and pressure, most real gases behave qualitatively like an ideal gas. Many gases such as air, nitrogen, oxygen, hydrogen, noble gases, and some heavier gases like carbon dioxide can be treated like ideal gases within reasonable tolerances.^[1] Generally, a gas behaves more like an ideal gas at higher temperature and lower density (i.e. lower pressure),^[1] as the work performed by intermolecular forces becomes less significant compared with the particles' kinetic energy, and the size of the molecules becomes less significant compared to the empty space between them. The classical ideal gas can be separated into two types: The classical thermodynamic ideal gas and the ideal quantum Boltzmann gas. Both are essentially the same, except that the classical thermodynamic ideal gas is based on classical statistical mechanics, and certain thermodynamic parameters such as the entropy are only specified to within an undetermined additive constant. The ideal quantum Boltzmann gas overcomes this limitation by taking the limit of the quantum Bose gas and quantum Fermi gas in the limit of high temperature to specify these additive constants. The behavior of a quantum Boltzmann gas is the same as that of a classical ideal gas except for the specification of these constants. The results of the quantum Boltzmann gas are used in a number of cases including the Sackur-Tetrode equation for the entropy of an ideal gas and the Saha ionization equation for a weakly ionized plasma.    

The compression process using ideal gas considerations results in work performed on the system and is essentially the area under a P-V curve. As can be seen in Figure 40, different amounts of work result from different ideal gas processes such as constant temperature and constant pressure.

Any equation that relates the pressure, temperature, and specific volume of a substance is called the equation of state. The following equation is the ideal-gas equation of state. A gas that obeys this relation is called an ideal gas.

Pv = RT

R is the gas constant, which is determined from

R = R_u/M

where,

R_u = universal gas constant, 8.314 kJ/(kmol-K)

M = molar mass, the mass of one mole of a substance in grams

The ideal-gas equation of state can also be expressed as

PV = mRT or PV = nR_uT

where,

m = mass of the gas

n = mole of the gas

The gas in an enclosed space, the situation is determined by the volume, pressure and temperature of the gas. By the law of Boyle-Gay Lussac, that the pressure (p), volume (V), and absolute temperature (T) of an ideal gas satisfy the relation:

p.V = nRT

By the law of Boyle-Gay Lussac, that the pressure (p), volume (V), and absolute temperature (T) of an ideal gas satisfy the relation:

p.V = nRT where, n=

 =

where,

p = gas pressure ( N/m² or Pa or atm)

V            = gas volume (m³)

n = amount of gas mole (mol)

R            = general gas constant (8314 J/kmol.K)

T = absolute temperature (K)

An ideal gas in a confined space can be changed situation through various processes such as isothermal process, the isokhorik, the isobaric, adiabatic process.

a.      Isothermal Process

Isothermal derived from the Greek, meaning the system state variables change at constant temperature.

From the figure shows that the pressure and volume changes along the trajectory of the system, while the temperature is fixed.

Because T is constant, then

p.v =  nRT = C = constant or p= C/V

The work done by the gas in the isothermal where,

W= nRTln

W= Work (joule)

b.      Isokhorik Process

Process isokhorik or isovolumetrik is the process of changing the system state variables at constant volume.

From the statement, we can describe the relationship between pressure chart with volume (pV)

From the graph shows that the pressure while the volume remains unchanged.

Because V is constant, then

 =

Due to the volume of gas does not change, then the work done by the gas is equal to zero.

W = p∆V = p x 0 = 0

c.       Isobaric Process

Isobaric process is a process of change in the system state variables at a constant pressure. From the statement, we can describe the relationship between pressure chart with volume (p-V).

From the graph shows that the volume changes while the pressure remains. Since P is constant, then

Since the gas pressure does not change, then the work done by:

W = p∆V = p (V₂- V₁)

d.      Adiabatic Process

An adiabatic process is any process occurring without gain or loss of heat within a system (i.e. during the process the system is thermodynamically isolated- there is no heat transfer with the surroundings). This is the opposite of a diabatic process, where there is heat transfer. A key concept in thermodynamics, many rapid chemical and physical processes are described or approximated in this way. Such processes are usually followed or preceded by events that do involve heat transfer (i.e. are non-adiabatic). Examples include electron-transfer.

PV^ϒ = constant

where P is pressure, V is volume, and

ϒ =  =

 being the specific heat for constant pressure,  being the specific heat for constant volume,  is the adiabatic index, and is the number of degrees of freedom (3 for monatomic gas, 5 for diatomic gas and collinear molecules eg. carbon dioxide).

CHAPTER III

CONCLUSION

1.      Ideal gas is a gas which has the following properties:

a.       Ideal gas composed of particles (atoms or molecules) whose numbers are plentiful and the particles do not occur between the attractive force.

b.      Each gas particle moves in the direction carelessly or randomly in all directions.

c.       Any collision that occurred lasted perfectly resilient.

d.      Gas particle evenly distributed throughout the room.

e.       The distance between the particles is much larger than the particle size.

f.       The volume of small molecules is a negligible fraction of the volume occupied by the gas.

2.      Gas  equation of state (real and ideal)

a.       In the ideal gas

PV = nRT

b.      In a real gas

3.     An ideal gas in a confined space can be changed situation through various processes such as isothermal process, the isokhorik, the isobaric, adiabatic process