Chemistry practical 2 - titration

Question 1

Aim of this experiment

Answer 1

To make a solution of a known concentration of ACID and use it to find the concentration of SODIUM HYDROXIDE solution

Question 2

How to prepare the standard solution: the solid acid

Answer 2

Weigh an empty test tube
Spoon approximately 2.5g of sulfuric acid into the tube and reweigh both the tube and acid

Question 3

How to prepare the standard solution: addition of the water to solid acid

Answer 3

Dissolve the weighed acid in 100cm3 of water in a beaker

Question 4

How to prepare the standard solution: volumetric flask

Answer 4

Transfer washings and the solution into a volumetric flask

Question 5

How to prepare the standard solution: dissolving water

Answer 5

Make up the solution to around 250cm3 in the volumetric flask with deionised water

Question 6

Step 1 of the actual titration - Preparing the burette

Answer 6

Rinse the burette with solution of standard solution
Because any remaining liquids in the burette may dilute the standard solution
Do not use water = diluted

Question 7

Step 2 of titration - preparing conical flask of unknown solution

Answer 7

Rinse volumetric pipette with unknown solution
If we use water, then this will dilute the solution because this well effect how many moles of unknown we add
Pour 25cm3 aliquot of unknown into conical flask
Add indicator

Question 8

Titrate what against what?

Answer 8

Titrate unknown in conical flask against the standard concentration solution in burette
Until colour change is observed, use white tile to observe colour change

Question 9

Can we wash the conical flask with water?

Answer 9

Yes because the moles of unknown have already been measured so remaining water molecules will not change number of moles

Question 10

Concordant results

Answer 10

Continue until 2 concordant titres have been obtained
Eg volumes within 0.10 cm3 of each other

Question 11

What happens if jet space in burette is not filled?

Answer 11

Errors in experiment as a larger volume reading of standard solution is added than reality

Question 12

Reading vs measurement

Answer 12

Reading is the single judgment taken straight from using a piece of equipment eg starting burette volume
Measurement is the difference in judgments of 2 values eg titre volume

Question 13

% uncertainty of a piece of equipment

Answer 13

uncertainty of equipment x number of times its read
divided by
Measurement taken
x100

Question 14

uncertainty of equipment

Answer 14

+- the smallest scale reading x number of times it is read

Question 15

Reduce uncertainties

Answer 15

decrease the sensitivity uncertainty by using apparatus with a greater resolution (finer scale divisions )
Or increase size of measurement made

Question 16

Percentage difference between actual vs calculated values (error)

Answer 16

Difference in values/ actual value
x100