unit 3.5

Question 1

what does avogadros law state

Answer 1

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

Question 2

formula relating volume, # of moles, and molar volume of gas at STP, how does this help us

Answer 2

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

Question 3

what are the temps, pressure of STP

Answer 3

temp: 0C or 273.15K
pressure: 100kPa

Question 4

define pressure

Answer 4

the force per unit area

Question 5

what is force a result of

Answer 5

an object hitting another object

Question 6

how does a balloon stay inflated

Answer 6

pressure inside>pressure outside
- collisions of gas particles w/ inside of walls are greater than outside

Question 7

define gas pressure

Answer 7

the force caused by the constant collisions b/w gas molecules and surface they come in contact w/

Question 8

what is gas pressure dependent on

Answer 8

• # of gas particles-> increased # of particles = increased frequency of collisions
• temperature->increased kinetic energy increases speed of particles<- more collisions

Question 9

what measures atmospheric gas pressure

Answer 9

barometer

Question 10

what is volume occupied by a gas dependent on

Answer 10

1. temp - as temp increases, molecules gain kin. energy and occupy more space
2. pressure - as pressure increases, molecules become more compressed, taking up less space
3. amount of gas - more gas = more space needed

Question 11

what does boyle’s law state

Answer 11

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)

Question 12

what is boyle’s law (formula)

Answer 12

P1V1=k
P2V2=k
P1V1=P2V2 <- inversely proportional

Question 13

what does charles’ law state

Answer 13

at constant pressure, the volume of a fixed mass of gas is directly proportional to its kelvin temp

Question 14

what is charles’ law (formula)

Answer 14

V1/T1=V2/T2

Question 15

what does gay-lussac’s law state

Answer 15

at a constant volume, the pressure of a mixed mass of gas is directly proportional to its temp

Question 16

what is gay-lussac’s law (formula)

Answer 16

P/T = k
P1T2=P2T1

Question 17

what laws does the combined gas law combine, what does it do

Answer 17

boyle’s law, charles’ law, gay-lussac’s law
- expresses relationship b/w pressure, volume, temp of fixed amount of gas

Question 18

what does dalton’s law of partial pressures state

Answer 18

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

Question 19

when is dalton’s law of partial pressures used

Answer 19

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

Question 20

what is the ideal gas law

Answer 20

hypothetical gas that obeys all the gas law perfectly under all conditions and conforms to the assumptions of KMT

Question 21

where is the ideal gas law formula derived from

Answer 21

combined gas law and avogadro’s law

Question 22

what is daltons law of partial pressure (formula)

Answer 22

Pgas = Ptotal - PH2O

Question 23

why is volume not additive when mixing solutes and solvents

Answer 23

• solute can fit in between spaces of larger particles (solvent)

Question 24

why is there a decrease in total volume of solution when NaOH is dissolved in water

Answer 24

Na+ and OH- are attracted to water molecules as they are ion dipoles

Question 25

what unit is used to measure concentration

Answer 25

mol/dm^3

Question 26

steps to make stock solution

Answer 26

1. measure mass of solution (determined by C+V) with weigh boat on scale 2. rinse volumetric flask w/ solvent + add a little solvent before adding solute 3. use quantitative transfer method to add solute until flask is halfway 4. hold base of flask neck and swirl steadily 5. ensure neck of flask is rinsed out + use dropper to fill to mark

Question 27

molality vs. molarity

Answer 27

mass per unit volume (g/dm^3)<- good for density vs. mol per unit volume (mol/dm^3)<- common

Question 28

define dilution

Answer 28

process of decreasing concentration of solution by adding more solvent

Question 29

what does dilution change, what does it not change

Answer 29

- moles of solutes stay the same - only concentration is changed

Question 30

what is the dilution equation

Answer 30

C1V1 = C2V2

Question 31

what is volumetric analysis

Answer 31

precise measurement of volumes to calculate the concentration of a solution

Question 32

what equipment is typically used for a titration

Answer 32

- beaker - erlenmeyer flask - graduated cylinder - volumetric flask - volumetric pipette - burette

Question 33

how does a titration work

Answer 33

a known concentration of base is placed in the burette (titrant) and is added to an unknown concentration (but known volume) of acid (analyte)

Question 34

what point do two solutions react completely in titration

Answer 34

equivalence point

Question 35

define titre

Answer 35

volume required to reach equivalence point of titration

Question 36

when does a titration end

Answer 36

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

Question 37

what do back titrations focus on

Answer 37

finding the amount of acid remaining after initial reaction

Question 38

when are back titrations typically used

Answer 38

- 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