1. Acids and Bases

2. Dissociation of Water
On average, 1 out of every 550 million water molecules dissociates (breaks down) into a hydrogen (H+) ion and a hydroxide (OH–) ion.
Water molecules are constantly dissociating and reforming
The OH- ion and the H+ ion easily react to create acids and bases

3. What is neutral?
When we say something is neutral, we mean that the concentration of H+ ions and OH- ions are equal.
[H+] = [OH–] [ ] = concentration
Water is a neutral compound, there are no excess H+ ions or OH- ions

4. What is an Acid?
An acid is a compound that dissolves in water to make a solution that contains more H+ ions than OH– ions.
Example: Hydrochloric Acid (HCl)
When dissolved in water HCl produces the H+ ion, making it an acid

5. Properties of Acids Create a sour taste in foods – fruits and candy
Dissolve metals and other materials
Cause serious skin and tissue damage

6. Common Acids Stomach Acid – Hydrochloric Acid (HCl)
Battery Acid – Sulfuric Acid (H2SO4)
Citric Acid – Sour taste in fruits
Acetic Acid – Vinegar

7. What is a Base?
A base is a compound that dissolves in water to make a solution that contains more OH– ions than H+ ions.
Example: Sodium Hydroxide (NaOH)
When dissolved in water
NaOH produces the OH- ion,
making it an base

8. Properties of Bases
Create a bitter taste in foods – herbs, coffee, nuts
Feels slick and slippery when handled
Cause serious skin and tissue damage

9. Common Bases Soap Baking Soda Bleach Ammonia – Fertilizer, cleaners
Magnesium hydroxide – antacids and laxatives

10. Strong vs. Weak Acids & Bases
Strong acids and bases
A strong acid or base dissociates completely in water so that each molecule contributes one H+ ion (acids) or one OH– ion (bases).
Weak acids and bases
A weak acid or base only dissociates partially or produces relatively few H+ or OH– ions in solution.

11. Acids & Bases Summary
Acids make more H+ ions and bases make more OH– ions.
The more H+ and OH– ions that are made the stronger the acid or base
Neutral substances have an equal amount of H+ ions and OH- ions
Acids Neutral Bases
[H+] > [OH-] [H+] = [OH-] [H+] < [OH-]

12. Alternate Definition of Acids & Bases
For a molecule or ion to act like an acid by donating a proton, another molecule or ion must act like a base by accepting the proton!
You cannot have something acting like an acid without something else acting like a base and vice versa.

13. Water
One of the most important properties of water is its ability to act as both an acid and a base.
In the presence of an acid, water acts as a base and accepts protons (H2O + H+ → H3O+)
In the presence of a base, water acts as an acid and donates protons (H2O → H+ + OH–)

14. The pH Scale
pH tells you whether a solution is an acid, a base, or neutral.
The pH scale ranges from 0 to 14.

15. The pH Scale pH Range Description Water is neutral and has a pH = 7
0 – 3
Strong Acid
4 – 6
Weak Acid 7
Neutral
8 – 11
Weak Base
12 – 14
Strong Base
Water is neutral and has a pH = 7
The further away you get from 7, the stronger the acid or the base becomes

16. pH Indicators- Litmus Paper
Red Litmus Paper
Stays red with an acid
Turns blue with a base
Blue Litmus Paper
Turns red with an acid
Stays blue with a base

17. pH indicator – pH paper
When the paper comes in contact with a chemical it turns the color of the pH.
Match the strip to the color key on the package

18. pH Indicator- Red Cabbage
Natural Indicator – use the juice of red cabbage to determine the pH of any substances

19. Calculating pH for Acids
To calculate pH, you must do the following: 1. Determine the molarity of H+ ions. 2. pH = –log(molarity of H+)
Example: A solution of acetic acid (HC2H3O2) has an H+ concentration of 5 × 10–5 M. What is the pH of the solution?

20. Calculating pH for Bases
To calculate the pH of bases you must do the following:
Find the concentration OH– ions
Use the equation pH = 14 + log[OH–]
Example: Find the pH of a M sodium hydroxide (NaOH) solution.

21. Calculators and solving for pH
If the concentration is in scientific notation…
Look for the EE button! Type 5 × 10–5 as 5E-5 OR
Use parenthesis! Type (5 × 10–5)

22. Calculators and solving for pH
2. Using the log button… Some calculators have you enter concentration first, then press log. Others you press log first and then enter the concentration. Don’t forget that finding pH of an acid it is a negative log!

23. Acid- Base Reactions
After the reaction is done both the acid and the base have been neutralized, and the solution now has a pH of 7