PAG 2 - Acid Base Titration Flashcards
What apparatus is used in a titration to accurately measure volumes
- Burette to measure the volume of solution added
- Pipette and pipette filter to measure a specific volume of solution into the conical flask
Describe how to carry out a acid-base titration
- Use a pipette to add 25 cm3 of acid into a conical flask. Add a few drops of indicator
- Pour alkali into the burette. Record the initial burette volume
- Complete a trial titre. The conical flask should be swirled constantly above a white tile. Stop adding the alkali as soon as the end point is reached. Record the final burette volume.
- Repeat the titration until two concordant results are obtained. Add alkali drop by drop near the end point
When transferring a solution from one beaker to another, how can you ensure as much of the dissolved substance has been transferred as possible?
Use distilled water to wash any leftover
solution from the old apparatus into the
new beaker
How do you accurately fill a volumetric
flask to the graduated mark?
Fill so the bottom of the meniscus rests
on the graduated mark.
The meniscus is the curve of the liquid.
Describe how to make a standard
solution of NaHCO3
- Weigh out a specified amount of NaHCO3
- Add a small volume of distilled water to the beaker containing the
NaHCO3 stir until completely dissolved - Use a funnel to add the solution to a 250cm3 volumetric flask
- Rinse the beaker with distilled water and add the washings to the flask
- Make the flask up to the graduation mark with distilled water
- Stopper the flask and shake the flask
Suggest 2 indicators that could be used
in an acid-base titration
- Phenolphthalein
2. Methyl orange
State the colour of phenolphthalein in:
a) Acidic conditions
b) Basic conditions
a) Pink
b) Colourless
State the colour of methyl orange in:
a) Acidic conditions
b) Basic conditions
a) Red
b) Yellow
(Orange at the end point of a titration)
What are concordant results in a
titration?
Titres that are within 0.1 cm3 of each other
What degree of precision should burette
readings be recorded to?
To the nearest 0.05 cm3
Which results are used when calculating
a mean titre?
2 concordant results (within 0.10 cm3 of each other)
When completing a titration, what piece
of apparatus is used to make the colour
change easier to observe?
A white tile
This is placed underneath the conical
flask.
What 3 things are required to take an
accurate burette reading?
- Read from the bottom of the meniscus
- Allow any liquid on the walls of the burette
to settle before taking a reading - Ensure there are no air bubbles
What is the end point of a titration?
The first point at which the indicator changes colour (permanently)
Why is the conical flask swirled during a
titration?
To ensure all the reactants are combined
so that the reaction is complete
