IDEAL GAS EQUATION AND ITS LAW

A hypothetical gas which obeys the law pv* = R*T at all the pressures and temperatures is called an ideal gas.

Real gases do not conform to this equation of state with complete accuracy. As p =0 , or T = infinity , the real gas approaches the ideal gas behaviour. In the equation, pv* = R*T, as T = 0, i.e, t = 273.15*C

if v* remains constant, p=0, or if p remains constant v* = 0. Since negative volume or negative pressure is inconceivable, the lowest possible temperature is 0K or -273.15*C. T is , therefore, known as the absolute temperature.

There is no permanent or perfect gas. At atmospheric condition only., these gases exist in the gaseous state. They are subject to liquefaction or solidification as the temperature and pressure are sufficiently lowered.

From Avagadro's law, when p= 760 mm Hg = 1.013 * 10^ 5 N/m 2

T = 273.15 K, an v* = 22.4 m3/ kg mol.

R* = 1.013 * 10^5 * 22.4 / 273.15

= 8314.3 Nm / kg mol K

= 8.3143 kJ / kg mol K

Since v* = V / n , where V is the total volume and n the number of moles of the gas, the equation of state for an ideal gas may be written as

pV = nR*T

Also n = m/ u ,

where u is the molecular weight.

pV = mR*T /u or

pV = mRT

where R = characteristic gas constant = R* / u

For Oxygen, e.g.,

Ro2 = 8.3143 / 32 = 0.262 kJ / kgK

for air, '

R air = 8.3143 / 28.96 = 0.287 kJ / kgK

There are 6.023 * 10^23 molecules in a g mol of a substance.

This is known as Avagadro's number (A).

A = 6.023 * 10^26 molecules / kg mol.

In n kg mole of gas, the total number of molecules, N, are

N = nA

n = N / A

pV = N R* T / A

= NKT

where K = Boltzmann constant

K = R* / A = 8314.3 / ( 6.023 * 10^26) = 1.38 * 10^-23 J / molecule K

There fore, the equation of a state of an ideal gas is given by

pV = mRT

= nR*T

= NKT

Comments

ELECTRICAL COMPARATORS AND ITS WORKING

Electrical Comparators are used as a means of detecting and amplifying small movements of a work contacting elements. An electrical comparator consists essentially of a pick-up head or transducer for converting a displacement into a corresponding change in current and a meter or recorder connected in the circuit to indicate the electrical change, calibrated to show in terms of displacement. Generally, an amplifier is needed to provide the requisite sensitivity and to match the characteristics of different parts of the circuit. Electrical comparators can be classified according to the electrical principle used in the pick-up head. Most of the comparators use either a differential transformer, an inductance bridge, a strain gauge or a capacitor as a means of detecting movement of the gauging element. There are different types of electrical comparators. One kind called an electrolimit gauge is used to check or measure the outside diameter of a roll. The objec...

SIMPLE CARBURETOR - CONSTRUCTION AND WORKING

CONSTRUCTION OF SIMPLE CARBURETOR : The main Components of Simple Carburetor are : Float Chamber, float, nozzle, venturi, throttle valve, inlet valve, and metering jet . In the float chamber, a constant level of petrol is maintained by the float and a needle valve. The float chamber is ventilated to atmosphere. This is used to maintain atmospheric pressure inside the chamber. The float which is normally a metallic hollow cylinder rises and closes the inlet valve as the fuel level in the float chamber increases to certain level. The mixing chamber contains venturi, nozzle and throttle valve. The venturi tube is fitted with the inlet manifold. This tube has a narrow opening called venturi. A nozzle is provided just below the centre of this venturi. The nozzle keeps the same level of petrol as that of the level in the float chamber. The mixing chamber has two butterfly valves. One is to allow air into the mixing chamber known as choke valve. The other is to al...

TOP POLLUTION RECORDED IN WORLD

CHERNOBYL NUCLEAR DISASTER (NUCLEAR POLLUTION) : In April 26,1986, the melt down of the Chernobyl nuclear reactor , in Russia, has leaked out the radioactive rays and radioactive materials. Effects : 1. In this Pollution nearly 2000 persons have been killed by the accident. 2. People suffered due to the illness such as, degeneration of the cells, severe bleeding, anemia, skin cancer. 3. Animals, Plants are also affected by nuclear radiation. MINAMATA EPIDEMIC (1953) : MARINE POLLUTION ( CASE STUDY ) Minamata is a small coastal village in Japan. The Chisso Chemical Company , which produces vinyl polymer plastics used organomercurial compound. The industry released its effluent into Minamata sea. The effluent containing mercury ions is converted into methyl mercury, which is highly toxic. The marine organisms like phytoplankton and zoo-planktons easily absorb the toxic methyl mercury compound. These organisms are consumed by small fishes and these are in ...

Mechinopedia For Mechanical Engineers

Search This Blog