Practicals

Question 1

What are the equipment needed for a titration?

Answer 1

funnel
100 cm3 conical flask
50cm3 burette
25cm3 pipette and filler
evaporating basin
alkali- sodium hydroxide solution
acid - hydrochloric acid solution
phenolphthalein indicator

Question 2

What are the safety considerations for a titration?

Answer 2

the acid and alkali can be irritant to the skin
phenolphthalein indicator can be flammable

Question 3

What is the method of a titration?

Answer 3

1. Using a pipette, measure 25.00 cm3 of NaOH solution and pour it into a conical flask.
2. Add two drops of phenolphthalein.
3. Pour the HCl solution into a burette.
4. Record the initial volume of HCl solution.
5. Add the hydrochloric acid from the burette into the conical flask a little at the time while
   swirling the conical flask.
6. When the phenolphthalein starts to turn from pink to colourless, add the HCl solution a
   drop at the time until one drop is sufficient to turn the solution colourless. Record the
   volume of HCl solution needed.
7. Carry out the titration again using 25.00 cm3 of NaOH solution and exactly the same
   volume of HCl solution.
8. Do not add indicator this time.
9. Gently heat the solution from the conical flask in an evaporating basin until its volume
   decreases by around a half.
10. Leave the evaporating basin to cool allowing crystals to form.

Question 4

What is the method of making a standard solution?

Answer 4

1. Accurately measure out the solid into a weighing bottle/boat
2. Record the mass with the correct number of significant figures
3. Transfer the solid into a 250 cm3 beaker and reweigh the bottle/boat and traces
4. Dissolve the solid with deionised water, stirring with a glass rod, ensure you do not add more than 150 cm3 of water at this stage
5. Pour the solution into the 250 cm3 volumetric flask via a funnel
6. Rinse the beaker and glass rod at least 3 times, and transfer the washings into the flask each time
7. Make the solution up to the mark with distilled water so that it is levelled with the bottom of the meniscus, using a Pasteur pipette for the final drops
8. Add the topper and shake the mixture thoroughly

Question 5

What indicator do you use when titrating a standard solution?

Answer 5

methyl orange