RP1- Standard Solution And Titration

Question 1

What is a standard solution?

Answer 1

A solution of known concentration

Question 2

Describe how to produce a standard solution

Answer 2

Weigh the mass of solid an weighing boat
Transfer the soldi to a beaker, reweigh the weighing boat and calculate the difference in mass
Dissolve the solid in de-ionised water. Stir with a glass rod until fully dissolved
Transfer solution to a 250cm3 volumetric flask (including washings of beaker and rod)
Fill the flask with more de-ionised water, until the meniscus sits on the graduated line
Stopper the flask and invert

Question 3

Describe a method for carrying out a titration

Answer 3

Pour 100cm3 of standard solution into a beaker

Rinse the burette with a small volume of the solution, fill the burette with standard solution using a funnel. Remove funnel and any air bubbles

Use a pipette and pipette filler to transfer 25cm3 of acid of unknown conc. into a 250cm3 conical flask (that has been rinsed with de-ionised water) . Add a few drops of phenolphthalein (it will remain colourless).

Record initial burette reading

Titrate the acid of unknown conc. until the solution turns light pink. Record the final titre.
(Wash sides of conical flask with de-ionised water, add drops slowly and continuously swirl flask)

Calculate titre volume, repeat until concordant results.
Use concordant results to find mean titre

Question 4

What are concordant results?

Answer 4

Results within 0.1cm3 of each other

Question 5

When finding percentage error, how do you know whether to times the uncertainty by the number of measurements taken.

Answer 5

If the uncertainty is for EACH reading, times by the number of readings

If the uncertainty is for the whole apparatus, do not times

Question 6

How can you reduce the uncertainty of the titre?

Answer 6

Use measuring cylinders and pipettes with lower uncertainties
For the burette, increase the volume of the titre. Do this by increasing the the volume of what is being neutralised, or increase the concentration

Question 7

What are safety precautions for this experiment?

Answer 7

Wear gloves and lab coat
Use lowest concentrations possible as acids and alkalis are corrosive and irritants

Question 8

How can you reduce the percentage uncertainty of a standard solution?

Answer 8

Use a more accurate weighing scale
Use larger masses of solid