Representative Gases

& Properties Of Gases Essay, Research Paper

Representative Gases & Properties of Gases

1. State the five assumptions of the Kinetic-Molecular Theory of gases.

a) Gases consist of large numbers of tiny particles. These particles, usually molecules or atoms, typically occupy a volume about 1000 times larger than occupied by the same number of particles in the liquid or solid state. Thus molecules of gases are much further apart than those of liquids or solids.

Most of the volume occupied by a gas is empty space. This accounts for the lower density of gases compared to liquids and solids, and the fact that gases are easily compressible.

b) The particles of a gas are in constant motion, moving rapidly in straight lines in all directions, and thus passes kinetic energy. The kinetic energy of particles overcomes the attractive forces between them except near the temperature at which the gas condenses and becomes a liquid. Gas particles travel in random directions at high speeds.

c) The collisions between particles of a gas and between particles and container walls are elastic collisions. An elastic collision is one in which there is no net loss of kinetic energy. Kinetic energy is transferred between two particles during collisions, but the total kinetic energy of the two particles remains the same, at constant temperature and volume.

d) There are no forces of attraction or repulsion between the particles of a gas. You can think of ideal gas molecules as behaving like small billiard balls. They move very fast, and when they collide they do not stick together, but immediately bounce apart.

e) The average kinetic energy of the particles of a gas is directly proportional to the Kelvin temperature of the gas. The kinetic energy of a particle (or any other moving object) is given by the equation: KE = 1/2mv2. Where m is the mass of the particle and v is the velocity.

2. List the five properties of gases (add the extra one too!)

a) Expansion Gases do not have a definite shape of definite volume. They fill the entire volume of an container in which they are enclosed and assume its shape. A gas transferred from 1-L to a 2-L vessel will quickly expand to fill the entire 2-L volume.

b) Fluidity Because the attractive forces between gas particles are negligible, gas particles glide easily past one another. This ability to flow causes gases to show mechanical behavior similar to that of liquids. Because liquids and gases flow, they are referred to collectively as fluids.

c) Low density The density of a substance in the gaseous state is about 1/1000 the density of the same substance in the liquid or solid state because the particles are so much farther apart in the gaseous state. For example, oxygen gas has a density of .001 g/mL, at 0.C and 1 atmosphere pressure. As

liquid at -183.C, oxygen has a density of 1.149 g/mL.

d) Compressibility During the compression of a gas, the gas particles which are initially very far apart, are crowded closer together. Under sufficient compression, the volume of a given sample of gas can be decreased thousands of times. The steel cylinders containing nitrogen, oxygen, or other gases under pressure that are widely used in industry illustrate this point. Such cylinders have internal volume of about 55 L. When they returned “empty” at ordinary pressures, they contain about 55 L of gas, although when they were delivered “full” they may have had 100 times as many molecules of gas compressed within the same cylinder.

e) Diffusion Gases spread out and mix with one another without stirring and in the absence of circulating currents. If the stopper is removed from a container of ammonia, the presence of this gas, which irritates the eyes, nose, and throat, soon becomes evident. Eventually, the ammonia mixes uniformly with the air in the room, as the random and continuous motion of the ammonia molecules carries them throughout the available space. The spontaneous mixing of the particles of two substances because of their random motion is referred to as diffusion.

f) Exertion Gases also have the ability to exert pressure on a surface.

3. Methods of production of the representative gases.

1) Balanced equations required:

a) Oxygen (2 methods): One method of preparation is decomposing hydrogen peroxide. Oxygen can be

prepared by passing hydrogen peroxide through a catalyst, manganese dioxide. It is then collected by

water displacement. The second method is decomposing water through electrolysis. Electricity is passes

though water, separating Hydrogen and Oxygen. Method 1: 2H2O2(aq) -MnO2 2H2O(l) + O2(g).

Method 2: 2H2O(l) -electrical energy 2H2(g) + O2(g).

b) Ozone (1 method): If enough energy is present, O2 will become O3. Method:

3O2(g) + energy 2O3(g).