Question | Answer |
What are the physical properties of gases | expand spontaneously to fill container
highly compressible
for homogeneous mixtures |
Why do gases exert pressure on any surface they come in contact with? | The gas molecules are in constantly colliding with the surface. |
atmospheric pressure | kinetic energy of the gas particles overrides the gravitation energy thus creating atmospheric pressure |
standard Atmospheric pressure | 1atm = 760 mmHg = 101.325 KPa |
Boyles Law | relationship between pressure and Volume
P1V1=P2V2
pressure increases so volume decreases |
Charles Law | relationship between temperature and volume
V1/T1=V2/T2
temperature increases so volume increase |
Avogardo's law | relationship between quantity and volume
the volume of ideal gas at constant temperature and pressure is directly proportional to the number of moles
double the number of moles the volume will double if T and P stay constant |
The ideal gas equation | PV=nRT
n=moles
R=gas constant |
STP | standard temperature and pressure
0 C (273K) and 1 atm |
combined gas law | PV and T are all constant
P1V1/T1=P2V2/T2 |
Gas densities and Molar mass | d=PM/RT
Density INCREASES with increasing P and M
Density DECREASES with increasing T |
volumes of gases in chemical reactions | air bags : 3 moles of N produced by 2 moles of NaN3
2NaN3(s) -> 2Na(s) + 2N3(g) |
Mixtures of different gases and partial pressures | three distinct gases with same V and T
all mix together all with their own pressures
Daltons law = PtV=ntRT .: Pt=P1+P2+P3.... |
P1/Pt= n1/nt
MOLE FRACTION | the total pressure is determined by the total number of moles of gas present, whether this is one gas or a mixture of gases. |
collecting gas over water | the total pressure of the gases inside is equal to the atmospheric pressure
Total pressure is the sum of the pressures and the water vapor ( on data table) |
Kinetic Molecular Theory | better describes physical properties of real gases
gases consist of large numbers of molecules in continous RANDOM motion
The combined V of all gas molecules are relative to the container
Attractive and repulsive forces between molecules are negligible |
Average Kinetic energy | Determined by temperature |
Molecular Speed | Boltzmann curves ( molecular speed vs. number of particles)
at high T's a large fraction of molecules move at greater speeds |
Root mean square (rms) speed . mew (u)
[speed of a molecule having average kinetic energy] | u= sqrt( 3RT/M)
Ek= 1/2mv^2
E= 1/2 mu^2 |
Real gases differences | real gas molecules occupy a finite space and they experience attractive forces |
Pressure difference | Greatest at high P
molecules that occupy large portion of container at high P thus greater than predicted for ideal gas
At Low P< 10atm difference is small |
Temperature difference | difference is greatest at lower T
- Cooling a gas decreases the avg Kinetic energy of the molecules attractive forces between the molecules stay constant and becomes dominate to the T that gas liquifies
- High T small difference due to the finite volume |
Van Der Waals | |