unit 3.5 Flashcards
what does avogadros law state
at the same temp and pressure, equal volumes of gas contain equal # of molecules <- therefore equal # of particles of all gases when measured at the same temp and pressure occupy equal volumes
formula relating volume, # of moles, and molar volume of gas at STP, how does this help us
Vm=V/n
Vm = 22.7dm^3/mol at STP
V = volume
n = moles
- allows relationship b/w gas volumes and reacting ratios in equations
what are the temps, pressure of STP
temp: 0C or 273.15K
pressure: 100kPa
define pressure
the force per unit area
what is force a result of
an object hitting another object
how does a balloon stay inflated
pressure inside>pressure outside
- collisions of gas particles w/ inside of walls are greater than outside
define gas pressure
the force caused by the constant collisions b/w gas molecules and surface they come in contact w/
what is gas pressure dependent on
- # of gas particles-> increased # of particles = increased frequency of collisions
- temperature->increased kinetic energy increases speed of particles<- more collisions
what measures atmospheric gas pressure
barometer
what is volume occupied by a gas dependent on
- temp - as temp increases, molecules gain kin. energy and occupy more space
- pressure - as pressure increases, molecules become more compressed, taking up less space
- amount of gas - more gas = more space needed
what does boyle’s law state
at a constant temp, the volume and pressure of a fixed mass or gas are inversely proportional (ex. volume inc while pressure dec. and vice versa)
what is boyle’s law (formula)
P1V1=k
P2V2=k
P1V1=P2V2 <- inversely proportional
what does charles’ law state
at constant pressure, the volume of a fixed mass of gas is directly proportional to its kelvin temp
what is charles’ law (formula)
V1/T1=V2/T2
what does gay-lussac’s law state
at a constant volume, the pressure of a mixed mass of gas is directly proportional to its temp
what is gay-lussac’s law (formula)
P/T = k
P1T2=P2T1
what laws does the combined gas law combine, what does it do
boyle’s law, charles’ law, gay-lussac’s law
- expresses relationship b/w pressure, volume, temp of fixed amount of gas
what does dalton’s law of partial pressures state
the total pressure of a mixture of non-reacting gases is equal to the sum of partial pressure of the individual gases when volume and temp are constant
when is dalton’s law of partial pressures used
when gas is collected over water <- gas displaces water generating small but sig amount of water vapour
- to subtract pressure exerted by water vapour to determine pressure of dry gas
what is the ideal gas law
hypothetical gas that obeys all the gas law perfectly under all conditions and conforms to the assumptions of KMT
where is the ideal gas law formula derived from
combined gas law and avogadro’s law
what is daltons law of partial pressure (formula)
Pgas = Ptotal - PH2O
why is volume not additive when mixing solutes and solvents
- solute can fit in between spaces of larger particles (solvent)
why is there a decrease in total volume of solution when NaOH is dissolved in water
Na+ and OH- are attracted to water molecules as they are ion dipoles
what unit is used to measure concentration
mol/dm^3
steps to make stock solution
- measure mass of solution (determined by C+V) with weigh boat on scale
- rinse volumetric flask w/ solvent + add a little solvent before adding solute
- use quantitative transfer method to add solute until flask is halfway
- hold base of flask neck and swirl steadily
- ensure neck of flask is rinsed out + use dropper to fill to mark
molality vs. molarity
mass per unit volume (g/dm^3)<- good for density vs. mol per unit volume (mol/dm^3)<- common
define dilution
process of decreasing concentration of solution by adding more solvent
what does dilution change, what does it not change
- moles of solutes stay the same
- only concentration is changed
what is the dilution equation
C1V1 = C2V2
what is volumetric analysis
precise measurement of volumes to calculate the concentration of a solution
what equipment is typically used for a titration
- beaker
- erlenmeyer flask
- graduated cylinder
- volumetric flask
- volumetric pipette
- burette
how does a titration work
a known concentration of base is placed in the burette (titrant) and is added to an unknown concentration (but known volume) of acid (analyte)
what point do two solutions react completely in titration
equivalence point
define titre
volume required to reach equivalence point of titration
when does a titration end
end point<- not the same as equivalence point
- molarity of analyte and titrant are not the same because visible change must occur<- more titrant than analyte
what do back titrations focus on
finding the amount of acid remaining after initial reaction
when are back titrations typically used
- insoluble compound where endpoint is hard to detect
- reaction too slow
- has impurities that interfere w direct titration
- contains volatile substances that may be lost during titration
