14. Neutralisation - titration curves

Question 1

the equivalence point is

Answer 1

the point in a titration at which the volume of one solution has reacted exactly with the volume of the second solution.
this matches the stoichiometry of the reaction taking place.

Question 2

the end point is

Answer 2

the point in a titration at which there are equal concentrations of the weak acid and its conjugate base forms of the indicator.
the colour at the end point is mid way between the colours of the acid and the conjugate base forms.

Question 3

purpose of a titration

Answer 3

determining the volume of one solution that reacts exactly with a known volume of another solution (equivalence point)

Question 4

acid- base titration curve

Answer 4

PH of the reaction mixture is measured as solution is added from the burette (using a PH meter)
PH can be plotted against volume of solution added producing an acid-base titration curve

Question 5

1. an acid-base indicator is a
2. it can be represented as
3. indicators and colour..
4. e.g. methyl orange
5. when is an indicator at its end point
6. what are end points accompanied by
7. most indicators change colour over a range of
8. where is the end point in the range

Answer 5

1. weak acid
2. HIn
3. one colour in acid form HIn
   and a different colour in conjugate base form In-
4. HIn red and In- yellow.
5. [HIn] = [In-]
6. a colour change
7. 2 PH units
8. usually in the middle

Question 6

choosing suitable indicator

1. PH value of the end point needs to be

Answer 6

1. as close as possible to PH of the equivalence point

Question 7

1. PH range of methyl orange

2. PH range of Phenolphthalein

Answer 7

1. 2-4

2. 8-10