RP1 - make up a volumetric solution and carry out a simple acid-base titration

Question 1

outline how you prepare a standard solution

Answer 1

1. weigh out an accurate mass of a solid in a dry, clean beaker
2. add enough deionised to dissolve the solid, stirring with a glass rod
3. transfer the solutions with rinsing to a 250cm3 volumetric flask using a funnel
4. rinse the beaker and glass rod with deionised watts and add to the volumetric flask
5. make up the mark by adding deionised water until the bottom of the meniscus is on the mark
6. stopper the flask and invert to mix thoroughly

Question 2

what is the equation for percentage error?

Answer 2

% error = error/ measurement x 100

Question 3

outline how you would perform a titration

Answer 3

1. fill up the Burnett with acid
2. use a pipette to add alkali to a conical flask. A volumetric flask is used to deliver a fixed volume of standard solution of alkali into a conical flask
3. Add an indicator to the alkali. An indicator is added to the alkali in the conical flask which causes a colour change
4. Slowly add the acid into the alkali
5. Slow the adding of acid when the changes colour
6. Stop adding the acid when there is a permanent colour change
7. The volume of acid delivered, known as the titre is recorded
8. Repeat the titration. It is repeated until concordant titres are obtained

Question 4

what is experimental error?

Answer 4

how close your value is to the true value expressed as a percentage

Question 5

what are the sources of error?

Answer 5

• air bubbles in burette
• funnel not removed
• inside of conical not washed
• not cleaning glassware
• adding too much indicator

Question 6

explain how air bubbles in the burette is a source of error and the effect it has on the tire volume

Answer 6

This would mean the level of the burette falls without adding any solution. The titre volume would be greater than expected

Question 7

explain how the funnel not being removed is a source of error and the effect it has on the titre volume

Answer 7

Drops from the funnel could add to the burette. Titre volume would be less than expected

Question 8

explain how not washing the inside of a conical flask is a source of error and the effect it has on the tire volume

Answer 8

• droplets from sides of the conical flask should be rinsed with distilled water to ensure all reactants mix
• titre volume would be greater than expected

Question 9

explain how not cleaning glassware is a source of error and the effect it would have on the titre volume

Answer 9

If you have trace amounts of substances which could react with the reagent, not cleaning means it could react with the reagent you are adding. This could cause a greater titre volume than expected.

Question 10

explain how adding too much indicator is a source of error and the effect it would have on the titre volume

Answer 10

Indicators are usually weak acids so adding too much could cause the titre volume to be inaccurate. This could make the tire volume less than expected

Question 11

define titration

Answer 11

a very accurate way to determine an unknown concentration of a substance