1. Water & pH Do Now: 11.16 OBJECTIVES: Define pH and the pH scale.
TASK: 1. List the 4 special properties of water we saw recently.
2. Make a prediction: place the following in order from the MOST acidic to the LEAST acidic:
Water, Soda, Coffee, Soapy water

2. Dissociation of Water – At any point in time, 1 in 10,000,000 water molecules split into H+ and OH-

3. pH scale: A before B

4. pH of Solutions… What is it?
What does it mean to be “acidic?”

5. pH Measures the Concentration of H+ ions
More H+  More acidic  Lower pH
More OH-  More basic  Higher pH
But it’s not a linear scale…

6. Arrhenius Acids & Bases
Acid: A substance which produces H+ when dissolved in water.
Base: A substance which produces –OH when dissolved in water.

7. pH measures H+ ACIDS BASES Low pH High pH Lots of H+ Little H+
Little -OH
Lots of -OH
Taste sour (e.g. lemon juice, vinegar)
Feel soapy (e.g. bleach)

8. Can You Spot the Patterns?
Concentration of H+ (mol/L)
Concentration of OH- (mol/L) pH
.000,000,000,001 (10-12)
.01 (10-2) 12
.000,000,000,01 (10-11)
.001 (10-3) 11
.000,000,000,1 (10-10)
.000,1 (10-4) 10
.000,000,001 (10-9)
.000,01 (10-5) 9
.000,000,01 (10-8)
.000,001 (10-6) 8
.000,000,1 (10-7) 7 6 5 4 3 2

9. Quick Math Refresher What is a logarithm
Quick Math Refresher What is a logarithm? It’s the opposite of an exponent. Log = 2 What’s the relationship?

10. The pH scale is logarithmic
pH = -log [H+]
[H+] = concentration of H+ in mol / L
Examples:
Neutral water: [H+] = 10-7 mol/L
-log 10-7 = 7
Vinegar: [H+] = 10-3 mol/L
-log 10-3 = 3
Notice: Even though there is10,000 times as much [H+] in the vinegar the pH is different by 4.
A change of 1 unit on the pH scale indicates a 10x change in ion concentration!

11. A Word About Hydrogen Ions and Hydronium
H+ is a proton.
In solution, H+ is always stuck to a water molecule (which part?)
Therefore, the following terms are all refer to what there is more of in an acid :
protons H+
Hydronium

12. Hydroxide and hydronium
Hydronium = H3O+. When extra H+ is put into a solution, it sticks to water to make this.
Hydroxide = -OH.