Neutralisation

Question 1

Describe how the pH reading changes as a base is added to an acid during a titration.

Answer 1

1. Initially pH increases slowly as the acid is greatly in excess
2. The pH then increases rapidly once a small volume of base has been added
3. The pH will then slowly increase as the base is now in excess

Question 2

What is the equivalence point on a pH curve?

Answer 2

The equivalence point of a titration is the volume of one solution which exactly reacts with the volume of another solution

• on a pH curve it is the centre of the vertical section

Question 3

How does the starting point of a pH curve differ depending on the strength of the acid?

Answer 3

Strong acid: starts at lower pH

Weak acid: starts at a higher pH ( still below 7 )

Question 4

How does the starting point of a pH curve differ depending on the strength of the base?

Answer 4

Strong base: starts at a higher pH

Weak base: starts at a lower pH ( still above 7 )

Question 5

What is an acid-base indicator?

Answer 5

A weak acid that has a distinctly different colour from its conjugate base

Question 6

What defines the suitability of an indicator?

Answer 6

The pH range of the indicator lies within the vertical section of the pH graph

Question 7

Why is no indicator suitable for a weak acid - weak base titration?

Answer 7

There is no vertical section of the graph