Titrations Flashcards
1
Q
Write a method.
A
- Use the pipette and pipette filler to put exactly 25 cm3 sodium hydroxide solution into the conical flask.
- Put the flask on a white tile.
- Clamp the burette vertically in the clamp stand. There should be just enough room underneath for the conical flask and tile.
- Close the burette tap.
- Use the small funnel to carefully fill the burette with dilute sulfuric acid. Before it completely fills put a small beaker underneath the tap, gently open it to allow acid to fill the tap, before closing again and filling the burette to the 0.00 cm3 line. Remove the funnel.
- Put 5–10 drops of phenolphthalein indicator into the conical flask. Swirl the flask to mix and put under the burette on top of the tile. The contents of the flask will go pink.
- Carefully open the burette tap so that 10 cm3 sulfuric acid slowly flows into the flask. Constantly swirl the flask when adding the acid. Then add the acid drop by drop until you see a permanent colour change from pink to colourless in the flask.You need to be able to shut the tap immediately after a single drop of acid causes the colour
to become permanently colourless - Read the burette scale carefully and record the volume of acid you added to 2dp
- Repeat until concordant results are reached.
2
Q
Why is universal indicator not used?
A
Does not give a clear endpoint
3
Q
What colour is phenolphthalein in alkali?
A
Pink
4
Q
Why is a pipette used?
A
To measure a fixed volume accurately
5
Q
Why is a burette used?
A
To accurately measure a variable volume
6
Q
Why is a conical flask used?
A
It allows the mixing of reactants without them spilling out
7
Q
Why is a white tile placed underneath?
A
To make colour change easier to see
8
Q
What are the rules to find an unknown concentration?
A
- Convert to dm3
- Work out known moles
- Molar ratio
- Find unknown concentration
- To convert to g/dm3 multiply concentration by Mr
