# set 4 – Chemistry Flashcard

 Gas LawsAvogadro Boyle Charles Dalton Gay LussacGraham
 Avagadro’s number is 6.022×10^23 [image];Boyle’s Law is P1v1=P2V2P=pressure V=volumeAt a fixed temperature, the volume of a gas is inversely proportional to the pressure exerted by the gas. Charles Law is (V1/T1)=(V2/T2)V=volume T=temperature“At a fixed pressure, the volume of a gas is proportional to the temperature of the gas. Dalton’s Law is Ptotal=P1+P2….P=pressure;Gay Lussac’s Law is (P1/T1)=(P2/T2)P=pressure T=temperature Graham’s Law is (Rate1/Rate2)=square root(mass2/mass1)The effusion rate of a gas is inversely proportional to the square root of its molecular mass.
 Kinetic Molecular Theory

### Postulates

1. Gases are composed of a large number of particles that behave like hard, spherical objects in a state of constant, random motion.
2. These particles move in a straight line until they collide with another particle or the walls of the container.
3. These particles are much smaller than the distance between particles. Most of the volume of a gas is therefore empty space.
4. There is no force of attraction between gas particles or between the particles and the walls of the container.
5. Collisions between gas particles or collisions with the walls of the container are perfectly elastic. None of the energy of a gas particle is lost when it collides with another particle or with the walls of the container.
6. The average kinetic energy of a collection of gas particles depends on the temperature of the gas and nothing else.

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 Partial PressuresThe pressure of a mixture of nitrogen, carbon dioxide, and oxygen is 150 kPa. What is the partial pressure of oxygen if the partial pressures of the nitrogen and carbon dioxide are 100 kPA and 24 kPa, respectively?
 ;P = Pnitrogen + Pcarbon dioxide + Poxygen150 kPa = 100 kPa + 24 kPa + PoxygenPoxygen = 150 kPa – 100 kPa – 24 kPaPoxygen = 26 kPa
 Van der Waals Equation

[P + (n2a/V2)](V – nb) = nRT

P=pressure

n=Number of moles

V=volume

T=temperature

R=ideal gas constant

a and b=constants, which are chosen to fit experiment as closely as possible to individual gas molecule.

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Tables of values for a and b are found in reference books. Below are some values for a and b. The units for a are liters2 atm. mole-2 and the units of b are liters mole-1.

 Molecule a b H2 0.2444 0.02661 O2 1.360 0.03183 N2 1.390 0.03913 CO2 3.592 0.04267 Cl2 6.493 0.05622 A 1.345 0.03219 Ne 0.2107 0.01709 He 0.03412 0.02370

 Graham’s Law
 Rate1 / Rate2 = square root of (Mass2 / Mass 1)Graham’s Law shows the relationship between the molar or molecular mass of a gas and the rate at which it will effuse. Effusion is the process of gas molecules escaping through tiny holes in their container.;
 Maxwell-Boltzman distribution
 The Maxwell distribution describes the distribution of particle speeds in an ideal gas.[image]Average SpeedThe average speed is the sum of the speeds of all of the particles divided by the number of particles.Most Probable SpeedThe most probable speed is the speed associated with the highest point in the Maxwell distribution. Only a small fraction of particles might have this speed, but it is more likely than any other speed.Width of the DistributionThe width of the distribution characterizes the most likely range of speeds for the particles. One measure of the width is the Full Width at Half Maximum (FWHM). To determine this value, find the height of the distribution at the most probable speed (this is the maximum height of the distribution). Divide the maximum height by two to obtain the half height, and locate the two speeds in the distribution that have this half-height value. On speed will be greater than the most probably speed and the other speed will be smaller. The full width is the difference between the two speeds at the half-maximum value.