Ideal Gas An ideal gas, as apposed to a real gas, does not condense at low temperatures, does not have forces of attraction or repulsion between the particles and is composed of particles that have no volume.

Ideal Gas Law The relationship between all four variables, temperature in Kelvin (T), volume (V), pressure (P) and number of moles (n). This relationship can be expressed as the ideal gas law: PV = nRT R is the proportionality constant. The value of R depends on the units used for pressure and volume. When pressure is in kPa, R is 8.314 (L x kPa)/(mol x K) but if pressure is measured in atmospheres it is .0821(L x atm)/(mol x K)

The ideal gas law works well for gases at room temperature and atmospheric pressure. If the volume decreases, or the pressure is extremely high then the real gas deviates from the ideal gas law

Gas Behavior Gases diffuse readily Diffusion – the movement of a substance from an area of high concentration to an area of low concentration. Particles with a low mass diffuse faster than particles with a higher mass. Diffusion of a gas increases entropy. Effusion – the passage of a gas under pressure through a tiny opening

Graham’s Law of Diffusion At a constant temperature and pressure, the rate of effusion of a gas is inversely proportional to the square root of the gas’s molar mass, M. This law also works for comparing rates of diffusion , and molecular speeds in general. Va = √Mb Vb √Ma

Gay-Lussac’s Law of Combining Volumes The law that states that the volumes of gases involved in a chemical change can be represented by the ratio of small whole numbers. Gas volumes correspond to mole ratios Ratios of gas volumes will be the same as mole ratios of gases in balanced chemical equations

Dalton’s Law of Partial Pressure The law that states that the total pressure of a mixture of gases is equal to the sum of the partial pressure of the component gases. Ptotal = PA + PB + PC