1. A- H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+
Strong acid A- H+
With a strong acid, the acid completely dissociates to form an anion and hydrogen ions.
The high H+ concentration causes a very low pH
The neutralise the acid, we need to add a lot of alkali… A- H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+
Add alkali

2. A- H2O A- H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+
Strong acid A-
H2O A- H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+
Add alkali

3. A- H2O A- H2O H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+
Strong acid A-
H2O A-
H2O H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+
Add alkali

4. A- H2O A- H2O H+ A- H+ H2O A- H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+
Strong acid A-
H2O A-
H2O H+ A- H+
H2O A- H+ A- H+ A- H+ A- H+ A- H+ A- H+ A- H+
Add alkali

5. A- H2O A- H+ H2O A- H2O H+ A- H+ H2O A- H+ A- H+ A- H+ A- H+ A- H+ A-
Strong acid A-
H2O A- H+
H2O A-
H2O H+ A- H+
H2O A- H+ A- H+ A- H+ A- H+ A- H+ A- H+
Add alkali

6. A- H2O A- H+ H2O A- H2O H+ A- H2O H+ A- H2O A- H+ A- H+ A- H+ A- H+ A-
Strong acid A-
H2O A- H+
H2O A-
H2O H+ A-
H2O H+ A-
H2O A- H+ A- H+ A- H+ A- H+ A- H+
Add alkali

7. A- H2O A- H+ H2O A- H2O H+ A- H+ H2O A- H2O A- H+ H2O A- H+ A- H+ A-
Strong acid A-
H2O A- H+
H2O A-
H2O H+ A- H+
H2O A-
H2O A- H+
H2O A- H+ A- H+ A- H+ A- H+
Add alkali

8. A- H2O A- H2O H+ A- H2O H+ A- H2O H+ A- H2O A- H2O H+ A- H+ H2O A- H+
Strong acid A-
H2O A-
H2O H+ A-
H2O H+ A-
H2O H+ A-
H2O A-
H2O H+ A- H+
H2O A- H+ A- H+ A- H+
Add alkali

9. A- H2O A- H2O H+ A- H2O H+ A- H2O H+ A- H2O A- H2O H+ A- H+ H2O A- H2O
Strong acid A-
H2O A-
H2O H+ A-
H2O H+ A-
H2O H+ A-
H2O A-
H2O H+ A- H+
H2O A-
H2O H+ A- H+ A- H+
Add alkali

10. A- H2O A- H+ H2O A- H2O H+ A- H2O H+ A- H2O A- H2O H+ A- H2O H+ A- H+
Strong acid A-
H2O A- H+
H2O A-
H2O H+ A-
H2O H+ A-
H2O A-
H2O H+ A-
H2O H+ A- H+
H2O A- H+
H2O A- H+
Add alkali

11. A- H2O A- H+ H2O A- H+ H2O A- H2O H+ A- H2O A- H2O H+ A- H+ H2O A- H2O
Strong acid A-
H2O
Success! The acid is neutralised.
> A- H+
H2O A- H+
H2O A-
H2O H+ A-
H2O A-
H2O H+ A- H+
H2O A-
H2O H+ A- H+
H2O A-
H2O H+

12. A- H+ HA HA HA HA HA HA HA HA HA Weak acid
With a weak acid, very little acid dissociates.
The modest H+ concentration causes the pH to be fairly low, perhaps about 3 or 4.
The neutralise the acid, we need to add alkali… HA HA HA HA HA HA HA HA HA
Add alkali

13. A- H2O A- H+ HA HA HA HA HA HA HA HA Weak acid
Neutralising the H+ causes more acid to dissociate: le Chatelier’s principle in action.
The neutralise the acid, we need to add more alkali… A- H+ HA HA HA HA HA HA HA HA
Add alkali

14. Weak acid A-
H2O A-
H2O H+ A- H+ HA HA HA HA HA HA HA
Add alkali

15. A- H2O A- H+ H2O A- H+ H2O A- H+ HA HA HA HA HA HA Weak acid
Add alkali

16. A- H2O A- H2O H+ A- H2O H+ A- H2O H+ A- H+ HA HA HA HA HA Weak acid
Add alkali

17. A- H2O A- H2O H+ A- H+ H2O A- H+ H2O A- H2O A- H+ HA HA HA HA
Weak acid A-
H2O A-
H2O H+ A- H+
H2O A- H+
H2O A-
H2O A- H+ HA HA HA HA
Add alkali

18. A- H2O A- H+ H2O A- H2O H+ A- H2O H+ A- H2O A- H2O H+ A- H+ HA HA HA
Weak acid A-
H2O A- H+
H2O A-
H2O H+ A-
H2O H+ A-
H2O A-
H2O H+ A- H+ HA HA HA
Add alkali

19. A- H2O A- H+ H2O A- H+ H2O A- H2O H+ A- H2O A- H2O H+ A- H2O H+ A- H+
Weak acid A-
H2O A- H+
H2O A- H+
H2O A-
H2O H+ A-
H2O A-
H2O H+ A-
H2O H+ A- H+ HA HA
Add alkali

20. A- H2O A- H+ H2O A- H2O H+ A- H2O H+ A- H2O A- H2O H+ A- H+ H2O A- H+
Weak acid A-
H2O A- H+
H2O A-
H2O H+ A-
H2O H+ A-
H2O A-
H2O H+ A- H+
H2O A- H+
H2O A- H+ HA
Add alkali

21. A- H2O A- H+ H2O A- H2O H+ A- H2O H+ A- H2O A- H2O H+ A- H2O H+ A- H+
Weak acid A-
H2O A- H+
H2O A-
H2O H+ A-
H2O H+ A-
H2O A-
H2O H+ A-
H2O H+ A- H+
H2O A- H+
H2O A- H+
Add alkali

22. A- H2O A- H+ H2O A- H+ H2O A- H+ H2O A- H2O A- H2O H+ A- H+ H2O A- H2O
Weak acid A-
H2O
Success! The acid is neutralised.
Notice that we have had to use the same volume of alkali to neutralise the weak acid, as we used for the strong acid.
The two acids had the same concentration, though one was weak and other was strong.
> A- H+
H2O A- H+
H2O A- H+
H2O A-
H2O A-
H2O H+ A- H+
H2O A-
H2O H+ A- H+
H2O A-
H2O H+