How do we measure Acids and Bases?

pH!

ACID BREATH!!!

CO2 + H2O --> H2CO3

H2CO3 + H2O --> HCO3- + H3O+

How is the acidity of something usually referred to?

The acidity of a chemical compound is determined by its location on the pH scale. On this scale, acids have a pH of 0-7, bases have a pH of 7-14, and neutral compounds

have a pH of exactly 7.000000.

H2O + H2O <--> H3O+ + OH-

Where do these numbers come from?

Self-Ionization of Water

http://videos.howstuffworks.com/science/ph-scale-videos-playlist.htm?page=2#video-18133

H2O + H2O <--> H3O + OH

Self-Ionization of Water

[H3O or H+] = 1.00 x 10 -7

[OH] = 1.00 x 10 -7

So if the [H+] goes up, then the [OH-] goes down.

pH = -log[H+][H+] = 10–pH

where [H+] is the molarity of the H+ ion in the solution. For strong acids, [H+] is the same as the molarity of the acid

solution.

pH = -log[H+]Sample: What’s the pH of a 0.0045 M HCl solution?

pH = -log[H+][H+] = 10–pH

Sample: What’s the concentration of a HCl solution that has a pH of 3.5?

Why do bases have pH values?In the ionization of water, we saw

the more OH- in the water the more basic it is.

pH = -log[OH+]pH + pOH = 14

.

pH = -log[OH+]pH + pOH = 14

What’s the pH of a 3.41 x 10-4 M NaOH solution?

pH practicePleas start on the pre-lab questions.

Once you have completed that I will pass out the materials.