Physical Behavior of Gases

Units of Measurement for Gases
same units as volume:
ml,cc,cm3, L
Temperature Units of Gases
gases must be measured in Kalvin:
C-K= C+ 273
F-K= [(F+40)5/9]-40+273
Absolute Zero
occurs at 0 K; all molecular motion ceases
STP(Standard Temperate Pressure) Conditions
T=0 C and P=1 atm
Pressure Units
atmosphere(atm), milimeters of mercury(mmHg/torr), pounds per in2(psi), kilopascals/kilopaskals(Kpa)
Pressure Unit Conversions
1 atm=760 mmHg/torr=14.7 psi=101.3 Kpa
Pressure
defines as force per unit area : P=F/A
Atmospheric Pressure
pressure that is exerted by the gas molecules in Earth’s atmosphere on its surface
Dalton’s Law of Partial Pressures
total pressures in any enclosed system is = to the total sum of the partial pressures (Pt=P1+P2+P3…Pn)
Kinetic Molecular Theory
explains gas behaviors in terms of molecular motion and distance
Four Basic Postulates of KMT
1) gas molecules are spaces far apart; gases are mostly empty space
2)gas molecules are in continuous, rapid, and linear motion(average speed of a gas molecule is 1000m/s)
3)pressure exerted by gases is a result of collision of gases(these are perfectly elastic) and no energy is lost
4) increase in temperature will increase the speed of gas molecules
Boyle’s Law
P1*V1=P2*V2(temperature is the constant variable)
*pressure is inversely proportional to volume
Charles’ Law
V1/T1=V2/T2( pressure is the constant variable)
*volume ans temperature are directly proportional
Gay-Lussac’s Law
P1/T1=P2/T2(volume is the constant variable)
*pressure and temperature are directly porportional
Combined Gas Law
P1*V1/T1=P2*V2/T2
Molecular Volume of Gases
*at constant temperature and pressure the volume is proportional to the mass
* molar volume is = to molar mass/density[(g/mole)/(g/)=L/mole
* all gases at the same temperature& pressure have the same molar volume
*molecular masses of 2 gases are in the same ratio as their densities (mm1/mm2=d1/d2)
Avogadro’s Hypothesis
1 mol of any gas under STP conditions will occupy a vol of 22.4L/mole
Ideal Gas Law(used when conditions are unchanging)
*assumes vol is proportional to the # of mols, absolute temp; is inversely proportional to pressure
PV=nRT(ideal gas aw equation)
P=pressure(atm), V=volume(L), n=# of mols, T=temperature(K), R= gas constant(0.0821)
PVM=gRT(alternate for ideal gas law equation)
*n is substituted by g/M(g=total mass of sample, M=molecular mass)
Ideal Behavior
gases behave ideally at high pressure conditions and low temperature conditions
Law of Combining Volumes
volume ratio is = to the mole ratio in a balanced chemical equation
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