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# How do we measure acids and bases

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### How do we measure acids and bases

1. 1. How do we measure Acids and Bases? pH!
2. 2. ACID BREATH!!! CO 2 + H 2 O --> H 2 CO 3 H 2 CO 3 + H 2 O --> HCO 3 - + H 3 O +
3. 3. 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.
4. 4. H 2 O + H 2 O <--> H 3 O + + 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
5. 5. H 2 O + H 2 O <--> H 3 O + OH Self-Ionization of Water [H 3 O or H+] = 1.00 x 10 -7 [OH] = 1.00 x 10 -7 So if the [H+] goes up, then the [OH-] goes down.
6. 6. 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.
7. 7. pH = -log[H + ] Sample: What’s the pH of a 0.0045 M HCl solution?
8. 8. pH = -log[H + ] [H + ] = 10 –pH Sample: What’s the concentration of a HCl solution that has a pH of 3.5?
9. 9. 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
10. 10. . pH = -log[OH + ] pH + pOH = 14 What’s the pH of a 3.41 x 10 -4 M NaOH solution?
11. 11. pH practice Pleas start on the pre-lab questions. Once you have completed that I will pass out the materials.