titration
Safety: Ensure tip of burette is not chipped or broken and that valve turns easily and smoothly. Wear safety goggles, apron and gloves. Keep phenolphthalein solution away from flames as it is flammable. Handle acids and bases carefully as they are corrosive. Rinse skin with lots of cool water if splashed with chemical and report any spills to the teacher immediately.
Source: Nelson Chemistry 11 (2010)
ACID BASE TITRATION
Purpose: To determine the concentration of solution of sodium hydroxide by acid-base titration and analyse the shape of a titration curve.
. Pre-Lab: / 11 I /8 K/U / 5 C
1) What colour is the indicator phenolphthalein in an acidic solution and in a basic solution? (2 K/U)
Phenolphthalein is colourless in acidic solutions and pinkish in basic solutions. 2) Why does the clear colour, which forms at the point where the hydrochloric acid comes into contact with the solution containing phenolphthalein and base in the receiving flask, disappear more slowly near the endpoint? (2I)
At the start of the titration, the NaOH solution in the flask will be pinkish and the pH is quite high. As HCl drops are added, the indicator colour will change momentarily to colourless as the pH is lower in the area around the drop(s). As the endpoint nears, the clear colour disappears more slowly as the solution has a lower pH than when the titration started.
3) What ions are taking part in the neutralization reaction? (2 I)
The ions taking part in the neutralization reaction are OH_ and H+. All ions are aqueous. Na+ and Cl_ are spectator ions and are not involved in the reaction.
4) In terms of the ions present, what has happened at the endpoint of the titration? (1 I
Bases dissociate to produce OH_ and acids ionize to produce H+ which creates water H2O.
5) Why is it a good idea to carry out titrations
Source: Nelson Chemistry 11 (2010)
ACID BASE TITRATION
Purpose: To determine the concentration of solution of sodium hydroxide by acid-base titration and analyse the shape of a titration curve.
. Pre-Lab: / 11 I /8 K/U / 5 C
1) What colour is the indicator phenolphthalein in an acidic solution and in a basic solution? (2 K/U)
Phenolphthalein is colourless in acidic solutions and pinkish in basic solutions. 2) Why does the clear colour, which forms at the point where the hydrochloric acid comes into contact with the solution containing phenolphthalein and base in the receiving flask, disappear more slowly near the endpoint? (2I)
At the start of the titration, the NaOH solution in the flask will be pinkish and the pH is quite high. As HCl drops are added, the indicator colour will change momentarily to colourless as the pH is lower in the area around the drop(s). As the endpoint nears, the clear colour disappears more slowly as the solution has a lower pH than when the titration started.
3) What ions are taking part in the neutralization reaction? (2 I)
The ions taking part in the neutralization reaction are OH_ and H+. All ions are aqueous. Na+ and Cl_ are spectator ions and are not involved in the reaction.
4) In terms of the ions present, what has happened at the endpoint of the titration? (1 I
Bases dissociate to produce OH_ and acids ionize to produce H+ which creates water H2O.
5) Why is it a good idea to carry out titrations