RP1- Titration Flashcards
Describe how you would make a volumetric solution
- weigh solid in weigh boat
- tip into beaker
- re-weigh weigh boat (then subtract any difference)
- dissolve in distilled water, stirring with stirring rod
- transfer with washings to a volumetric flask and make up to line
How close are concordant results?
within 0.05
Explain how to calculate percentage uncertainty from a burette
reading
1/2 the smallest division, *2 because it is read twice
What happens to a titration result if the air bubble is not removed
from the tap?
The volume added is less than expected
Explain how to set up a clean burette with acid in it
1) wash with distilled water
2) wash with acid
3) wash through the tap with acid
4) fill up with acid
5) run through the tap to make sure air bubble is removed
How would adding too much indicator impact the titration?
indicators are acidic or basic in themselves, so could react and impact the endpoint reading
Why would you NOT use a measuring cylinder?
has a large uncertainty/not accurate enough
What would you use instead of a measuring cylinder?
volumetric pipette
Why is rinsing with distilled water ONLY an issue?
as it could dilute the solution
Why might adding the solution until it ‘just’ changes colour lead to inaccurate results?
as it may not have fully reacted, so must be added until there is a permanent colour change
How do you calculate percentage uncertainty?
(uncertainty/measurement made) *100
What is the uncertainty of a 25cm3 pipette?
+- 0.1cm3
What is the uncertainty of a burette?
0.05 for each reading, read twice so 0.1
What is the uncertainty of a 3.d.p balance?
0.001g
How could you reduce % uncertainty?
use apparatus with smaller resolutions or increase measurement made
Why must the jet space be filled properly?
lead to a larger than expected titre reading
What indicator can be used when adding acid to an alkali? What colour change would happen?
phenolphthalein, pink to colourless
What indicator can be used for neutralisation reactions where strong acids are used? What colour change would happen?
methyl orange, red in acid, yellow in alkali. Orange at the end point
Why would rinsing with distilled water at the end of a titration not impact the results?
water does not react with reagents, change in the number of moles acid added
Why is an acid-base indicator used?
to detect when a reaction reaches completion, usually with a colour change
