# chem chapter 5

 characteristics of gases made up of all nonmetalslow MW compoundsexpand to fill a containergases are compressiblegases mix homogeneously when combined vapor gas of a compound that is liquid at the given temperature why does a balloon expand when you blow into it? increase in pressure because of more gas molecs colliding with the walls atmosphere gases in atmosphere are "pulled" toward earth by gravity --- causing pressurehow is it measured?barometerusually measured in atm barometer how atmosphere is measured 1 atm standard atmospheric pressureenough pressure to push mercury(Hg) column to a height of 760mmHg = 760 torr 1atm = 760mmHg = 760 torr how is pressure in a closed system measured? manometer open-ended column *units have to be the same for Pgas & Patmdelta(h) = difference in heights if column heights are equal: Pgas = Patm if Patm > Pgas Pgas = Patm - delta(h) if Patm < Pgas Pgas = Patm + delta(h) closed manometer *atmospheric pressure does not matter vacuum is on "open" endvacuum: absence of any molecs0 pressureGas must push harder than vacuum to have pressure Pgas = delta(h) four variables with gases T = temp, must be in Kelvin(K)P = pressureV = volumen = # of moles of gas present (never a gram relationship) ideal gas law PV=nRT R, ideal gas constant...use block!! or 0.08206L*atm/mol*K 22.4L*1atm1mol*273K 1atm = 760mmHg(or torr) = 101.3kpa relate V and P P1V1 = P2V2V goes up, P goes down relate V and T V1/T1 = V2/T2V goes up, P goes up relate V and n V1/n1 = V2/n2V goes up, n goes up facts while the MW of gases can vary significally, the volume depends only on the number of particles of gas present (moles)weights vary (because of MW), but at STP, 1 mole of gas will always have the same volume. ideal gas definition hypothetical gas that behaves according to the ideal gas law (PV= nRT) density mass per unit volume (mass/volume) dgases = g/L dliquids = g/mL OR d = P(MW)/ RT rearrange density equation to equal MW original: d = P(MW)/RT rearranged:MW = dRT/P more than one gas present: each gas acts like it's alone identity of molecs of gas is not important dalton's law of partial pressures the total pressure of a mixture of gases is the sum of the partial pressure of gases in the mixture P = nRT/V *pressure depends on the number of molecules/atoms or moles of gas present kinetic molecular theory a way to visualize what the molecules are doing AuthorAnonymous ID45837 Card Setchem chapter 5 Descriptionoctober 28, 2010 Updated2010-10-29T04:28:39Z Show Answers