required practical 1: acid-base titration Flashcards
procedure of making a 250 cm3 solution
weigh mass of solid on a balance.
transfer to beaker and dissolve sample with minimum volume of deionised water
transfer sample to 250cm3 volumetric flask with washings and make up to 250cm3
invert volumetric flask
procedure for titration
add 25cm3 of alkali to conical flask using glass pipette
add acid to burette
ensure jet is filled
add indicator to alkali
place white tile under conical flask
add acid whilst swirling mixture
note burette reading at bottom of the meniscus at the start and end
repeat until at least 2 concordant results
what happens to reading in jet is not filled
errors during titration and end value - larger than actual value of titre
colour change of pheolphthalein
pink - colourless
alkali - acid
colour change of methyl orange
yellow - orange - red
alkali - midpoint - acid
why can distilled water be added to conical flask for washing
wont affect mole of acid needed as the water wont react with the reactant
why is acid added in dropwise near endpoint
so you dont go past the end point
formula for uncertainty
uncertainty / measurement X 100
how is uncertainty reduced during titration + measuring mass
use apparatus with lower uncertainty
increase volume or concentration of substance in conical flask
decrease concentration of substance in burette
use balance which measures to more decimal places
why does keeping a funnel in the burette affect final titre value
solution may continue to drip down into the burette during the titration
why are conical flasks used instead of beakers
less likely to spill when swirling solution
if there is 0.0014 moles in 26.45cm3, how many moles are in 250cm3
(0.0014/26.45) X 250
how does an air bubble affect final titre and average
increases final titre as the bubble takes up space of solution.
if the air bubble is only in the first titre it will not affect average, as the rough titre is not included in result of mean titre
