Titration Required Practical

Question 1

What is the practical method?

Answer 1

1. Use volumetric pipette + pipette filler to add 25cm3 of sodium hydroxide to a clean conical flask
2. Add 3-4 of phenolphthalein to the conical flask and place on white tile
3. Fill burette with hydrochloric acid - record the starting volume
4. Slowly open tap and add the acid to the conical flask, constantly swirling to mix
5. When colour change first noticed, add the acid from the burette drop wise
6. Stop adding the acid when the end-point is reached and record your final volume
7. Repeat steps until you get concordant titres (within 0.10 ml)
8. Calculate mean using concordant results - record volume used to neutralise the alkali

Question 2

What safety precautions must be taken?

Answer 2

• Wear goggles
• Use of pipette filler - don’t come into contact with acids/alkali to avoid irritation to skin
• Fill the burette slowly below eye level, using a funnel
• Gentle swirling to avoid splashes

Question 3

What is endpoint? When can this be seen?

Answer 3

When a neutral solution is created. This can be seen because there is a permanent indicator colour change.

Question 4

Why is a white tile used?

Answer 4

To see colour change clearly

Question 5

Why is a burette used?

Answer 5

• Can be used to measure variable volumes
• Can be controlled by adding drop wise

Question 6

Why is a volumetric pipette used?

Answer 6

Used to measure a fixed volume