Acids, Bases, pH
􀁡H2O + H2O = H3O + and OH 􀁡by convection we write:
H2O = H + and OH 􀁡pH = 7, neutral ,at equilibrium, [H + ] = [OH
-]
pH
Scale = 0-14
􀁡acid: dissociates H + , pH below 7,
eg. HCl = H + and Cl 􀁡base: dissociates OH - accepts H + ,pH
above 7
ex. NaOH = Na + and OH ex. NH3 + H = NH4
Measuring pH using plant pigment
4.1 and 4.2
Anthocyanins = plant pigments in cabbage
used as pH indicator eg red at low pH
􀁡Procedure:
􀁡make standards with the following pH
buffers and record their color:
2, 4, 6, 7, 8, 10, 12.
Compare unknown(4.2)
Ex 4.3
The pH meter is more accurate than plant
indicators.
􀁡Procedure:Calibrate pH meter using pH 4
and pH 7
Determine pH of substances with pH meter
and pH paper
Buffers- 4.4
Buffer: prevents sudden pH changes
􀁡
􀁡Procedure:􀁡determine
the buffering
capacity of two substances (A & B)
Follow the book instructions
􀁡Graph your results for A & B
􀁡Record which is the better buffer
4.5 How Effective are Stomach
Antacids- Instructor demo
Antacid: used to neutralize excess acid
􀁡Procedure:􀁡ompare different antacids
Rolaids, Tums, Alka-Seltzer
􀁡determine effectiveness of antacids per
gram( use 0.5 grams of each)
􀁡run a control