Gen CHEM 2

• Gases do not have a definite shape or volume
• All gases uniformly fill any container
• Gases exert a pressure on the surroundings
• Volume is significantly affected by temperature and pressure
• All gases mix together in any proportion
• Gases are considerably less dense than solids or liquids
• Pressure equals force divided by unit area
• Force equals mass times acceleration
• Acceleration is 9.8m/s^2
• 1 normal atmosphere is 1 atm
• 1 standard temperature is 1 bar
• Barometer measures atmospheric pressure
• Pressure exerted by the environment is measured with a barometer
• Boyles law: pressure is inversely proportional to volume
• Charles law: volume is porportional to temperature
• Moveable piston in a question equals constant pressure
• Avogadros Law: volume is directly proportional to the number of moles of gas
• Amontons Law: pressure is proportional to temperature (moles and volume are fixed)
• The Ideal gas law allows the calculation of gas properties when more than one variable is changing
• Standard temperature and pressure is when pressure equals 1 bar, and Temperature equals 273.15K
• Standard Ambient Temperature and Pressure, is when pressure equals 1 bar and temperature equals 298.15K (25 degrees celsius)
• Molar Volume (L/mol) is the volume occupied by one mole of an ideal gas at STP
• If an item is less dense than water it will float
• Density equals mass/volume
• When pressure is in atm and Temperature is in K, density is in g/L (gases)
• In general the density of compounds is g/cm^3 (solids)
• Buoyancy depends on differences in gas densities (molar masses and temperature)
• Charles law: Density decreases as Temperature increases
• Daltons Law: for a mixture of gases in a container Ptotal= p1+p2+p3, etc, pressure depends on the moles total not the identity of the gas
• Mole Fraction: ratio of the number of moles of a component in a mixture to the total number of moles in a mixture
• There is 1 bar in 100 millibars
• Anytime any of the diatomic elements are in a question assume they are diatomic and not a single element
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  Collecting a gas over water means Ptotal= Po2 + Ph2o, go to vapour pressure table
• Gas molecules do not interact at STP but will interact at higher pressures
• At height pressure and low temperature attractive and repulsive forces between gas molecules become significant
• CH4 and CO2 deviate from ideal gas behaviour as they like the be compressed
• Van der Waals equation is used at high pressure and low temperatures
• In Van Der Waals equation a corrects for attractive forces that affect pressure
• In Van Der Waals equation b corrects for volume occupied by molecules
• Van Der Waals equation will solve for pressure