1. Equivalence Point

2. Definition
Equivalence Point: the stoichiometric end of a neutralization reaction.
Example: NaOH + HCl  H2O + NaCl
What is the mole ratio for the entire reaction?
The Equivalence Point would be when 1 mol NaOH and 1 mol HCl produce 1 mol H2O and 1 mol NaCl.

3. How do we know when we have reached the equivalence point?
We use a graph.

4. Equivalence Point and ions (HCl + NaOH)
Notice the equivalence point. Is the equivalence point the same as the endpoint?
What is the balanced equation for this reaction?
HCl + NaOH  NaCl + H2O
Notice the acid is completely dissociated.
Notice the equivalence point. What is the mole ratio?

5. Another Example (CH3COOH + NaOH)
Notice the equivalence point. Is the equivalence point the same as the endpoint?
What is the balanced equation for this reaction?
CH3COOH + NaOH  CH3COONa + H2O
Notice the acid is NOT completely dissociated.
Notice the equivalence point. What is the mole ratio?

6. How do you find the equivalence point on a graph?
For you, this is not exact.
Look at the vertical part of the graph.
Draw a line at the top of the vertical part.
Draw a line at the bottom of the vertical part.
Half-way between the two lines is your equivalence point.
Equivalence Point

7. Another example Look at the vertical part of the graph.
Draw a line at the top of the vertical part.
Draw a line at the bottom of the vertical part.
Half-way between the two lines is your equivalence point.
Equivalence Point

8. Last Example What is the balanced equation for this reaction?
How many equivalence points are there?
Determine the H2PO3-1 equivalence point by drawing on the graph.
Determine the HPO3-2 equivalence point by drawing on the graph.
What is the pH of the H2PO3-1 equivalence point?
What is the pH of the HPO3-2 equivalence point?