Saturday, July 21, 2012

Chapter Six chemistry note



·         Kinetic Molecular Theory of Gases
o   Gas consist of small particles that move randomly with rapid velocities, causing it to fill any container it’s in
o   The attractive forces between the particles of a gas can be neglected
o   The actual volume occupied by gas molecules is extremely small compared to the volume that gas occupies
o   The average kinetic energy of gas molecules is proportional to the Kelvin temp
·         Gas is described in four properties, pressure, volume, temperature, and amount
·         Gas particles move fast, as more molecules strike the wall, the pressure increases. If the container is heated, the molecules move faster
·         The pressure exerted by the air is called atmospheric pressure. This is the most common unit used or mmHg (millimeters of Mercury)
·         The volume of gas equals the size of the container in which the gas is placed
·         When temperature is involved with gas, it needs to be changed to Kelvin by adding 273 to the degrees Celsius
·         Pressure is the force exerted by gas against the walls of the container. It’s measured using ATM, mmHg, or torr.
o   P = force/area
·         1 ATM = 760 torr = 1mmHg
·         Volume is the space occupied by gas and is measured by L and mL
·         Temperature determines the kinetic energy and rate of motion of the gas particles, mostly measured in C and K, K is required to calculate
·         Amount is the quantity of gas present in a container and is measured in g and moles, moles are required for calculations
·         Boyle’s Law says that volume changes inversely with pressure. If the volume of the container is decreased than the pressure of the gas will increase as long as there has been no change in temp or gas amount
o   P1V1 = P2V2; use this formula when a pressure question is asked
·         Charles Law relates to temp and volume, in which the volume is increased when temp is increased, but no change in pressure or amount of gas is included
o   V1/T1 = V2/T2; use this when volume and temp are referenced to *****don’t forget to change the temperature to Kelvin*****
·         Gay-Lussac’s Law states that the pressure of a gas is directly related to its Kelvin temperature meaning, an increase in temperature increases the pressure and a decrease in temp decreases the pressure of gas, as long as the moles and volume remain the same.
o   P1/T1 = P2/T2; use this when temp and ATMs of pressure are being asked.
·         All pressure-volume-temperature relationships for gases that we have studied may be combined into a single relationship called the combined gas law. This expression is useful for studying the effect of changes in two of these variables on the third as long as the amount of gas remains constant.
o   1V1/T1 = P2V2/T2; use this when two of the variables are used
·         One mole is 22.4L of any gas
·         The total pressure is the sum of each gas

·         Avogadro’s Law states that if the number of moles is doubled than the volume will also double as long as we don’t change the pressure or the temperature
o   V1/n1 = V2/n2
·         Many gases are a mixture; therefore the total pressure of gases in a mixture is a result of the collisions of the gas particles regardless of what type of gas they are.
·         In a gas mixture, each gas exerts its partial pressure, which is the pressure it would exert of it were the only gas in the container.
·         Dalton’s Law states that the total pressure of a gas mixture is the sum of the partial pressures of the gases in the mixture
o   PTOTAL = P1 + P2 + P3 …..

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