1
Q
What are the equipment needed for a titration?
A
funnel
100 cm3 conical flask
50cm3 burette
25cm3 pipette and filler
evaporating basin
alkali- sodium hydroxide solution
acid - hydrochloric acid solution
phenolphthalein indicator
2
Q
What are the safety considerations for a titration?
A
the acid and alkali can be irritant to the skin
phenolphthalein indicator can be flammable
3
Q
What is the method of a titration?
A
- Using a pipette, measure 25.00 cm3 of NaOH solution and pour it into a conical flask.
- Add two drops of phenolphthalein.
- Pour the HCl solution into a burette.
- Record the initial volume of HCl solution.
- Add the hydrochloric acid from the burette into the conical flask a little at the time while
swirling the conical flask. - 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. - Carry out the titration again using 25.00 cm3 of NaOH solution and exactly the same
volume of HCl solution. - Do not add indicator this time.
- Gently heat the solution from the conical flask in an evaporating basin until its volume
decreases by around a half. - Leave the evaporating basin to cool allowing crystals to form.
4
Q
What is the method of making a standard solution?
A
- Accurately measure out the solid into a weighing bottle/boat
- Record the mass with the correct number of significant figures
- Transfer the solid into a 250 cm3 beaker and reweigh the bottle/boat and traces
- 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
- Pour the solution into the 250 cm3 volumetric flask via a funnel
- Rinse the beaker and glass rod at least 3 times, and transfer the washings into the flask each time
- 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
- Add the topper and shake the mixture thoroughly
5
Q
What indicator do you use when titrating a standard solution?
A
methyl orange
