PROPERTIES OF GASES AND GAS MIXTURE
n = number of moles
m is mass of the gas m = nM
Rair = 0.287 kJ/kg K
Mair = 28.96
g= Adiabatic constant
| value of|
The Ideal Gas Law is based on the assumptions that gases are composed of point masses that undergo perfectly elastic collisions. However,real gases deviate from those assumptions at low temperatures or high pressures. Imagine a container where the
pressure is increased. As the pressure increases, the volume of the container decreases. The volume occupied by the gas particles is no longer negligible compared to the volume of the container and the volume of the gas particles needs to be taken into account. At low temperatures, the gas particles have lower kinetic energy and do not move as fast. The gas particles are affected by the intermolecular forces acting on them, which leads to inelastic collisions between them. This leads to fewer collisions with the container and a lower pressure than what is expected from an ideal gas.
Adhesive and Cohesive Forces
Cohesive forces are the intermolecular forces (such as those from hydrogen bonding and Van der Waals forces) which cause a tendency in liquids to resist separation. These attractive forces exist between molecules of the same substance. For instance, rain falls in droplets, rather than a fine mist, because water has strong cohesion which pulls its molecules tightly together, forming droplets. This force tends to unite molecules of a liquid, gathering them into relatively large clusters due to the molecules' dislike for its surrounding.
Adhesive forces are the attractive forces between unlike molecules. They are caused by forces acting between two substances, such as mechanical forces (sticking together) and electrostatic forces (attraction due to opposing charges). In the case of a liquid wetting agent, adhesion causes the liquid to cling to the surface on which it rests. When water is poured on clean glass, it tends to spread, forming a thin, uniform film over the glasses surface. This is because the adhesive forces between water and glass are strong enough to pull the water molecules out of their spherical formation and hold them against the surface of the glass, thus avoiding the repulsion between like molecules.
Pc, Vc, Tc = critical pressure volume and temperature of the gas
For homogenous mixture of ideal gases in a container, if P1, P2, P3... are pressure for the gases when they remain alone in the container. The total pressure in the container at the same temperature is
n1, n2, n3 ....... = number of moles of gases
x1, x2, x3 ....... = mole fractions of gases