KINETIC MOLECULAR THEORY OF GASES
1. Gases consist of tiny particles (which may be atoms or molecules), which are in constant random motion
2. Interactions between gas particles are small compared to their kinetic energy
3. The volume of the particle is neglible compared to the volume of the container they are in
4. Pressure is caused by molecules colliding with walls of the container (and no energy is lost in the process
5. Temperature is a measure of the average kinetic energy of the moving particles.
Molecular motion
Speed of molecules in air. Air is mostly nitrogen N1, M=28g/mol = 0.028kg/mol. At room temp of ~298K, predicted v is 515m/s, experimental v is 340m/s.
As the temperature of gas increases, particle speed also increases
T is proportional to v
T ~ v
Increased v increases number of collisions between the particles and the walls of the container
Hence increased T = increased P
T ~ P
Changing container size
If the size of the container increases, the number of collisions per unit time will decrease slightly, proportional to the density decrease.
If the size of the container decreases, the total number of collisions per unit time will increase slightly, proportional to the density increase.
Number of collisions per unit area.
Area has been increased – container volume. When V increases, density of gas decreases only slightly but the surface area of the container increases substantially, thus the number of collisions per unit area decreases significantly, just because there is so much additional surface area
Thus decrease volume – pressure increases.
V ~ 1/P
Add more gas molecules in rigid container = pressure increases, more collisions with the walls in total thus more collisions
Pressure – collisions per unit area
Add gas to a flexible container
Initially – pressure inside the balloon will increase. As there are more collisions with walls of the container. The volume will then increase because the force on the inside walls will be GREATER than force on outside. After balloon stops expanding, the pressure on the inside and outside equalise (otherwise unequal forces would still cause it to expand) so all the change in the number of moleucles will result in a volume increase only.
MIXTURE OF GASES
Daltons law
Physical/ chemical separation techniques
List + explain principles behind different carbon capture and storage technologies
DALTONS LAW
Total pressure exerted by a mixture of gases is the sum of the partial pressures of each individual gas
Ptotal = P1 + P2 .... + Pn
The parital pressure of a gas is the pressure that would be exerted by the gas if it were alone in the container
