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Goals to Accomplish Today 5.18.12. Go over pg. 74-75 and concept review Lecture: Indicators and pH (A) pg. 76-77. Universal Indicator. Acids. Bases. Phenolpthalein Indicator. Identifies if a base is present: turns pink. Litmus Paper- tells you if you have an acid or a base.
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Goals to Accomplish Today 5.18.12 • Go over pg. 74-75 and concept review • Lecture: Indicators and pH (A) pg. 76-77
Universal Indicator Acids Bases
Phenolpthalein Indicator Identifies if a base is present: turns pink
What is the pH scale and what am I really measuring? • A value to express the acidity of a solution (power of hydrogen) • Ranges from 0-14 • 0-6 Acidic • 7 Neutral • 8-14 Basic • Measures the hydronium ions in a solution • The more hydronium ion the more acidic
pH scale : measures acidity/basicity
pH scale : measures acidity/basicity Soren Sorensen (1868 - 1939) ACID BASE 10x 10x 10x 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 NEUTRAL Each step on pH scale represents a factor of 10. pH 5 vs. pH 6(10X more acidic) pH 3 vs. pH 5 (100X different) pH 8 vs. pH 13 (100,000X different)
pH of Common Substances water (pure) 7.0 vinegar 2.8 soil 5.5 gastric juice 1.6 carbonated beverage 3.0 drinking water 7.2 bread 5.5 1.0 M NaOH (lye) 14.0 blood 7.4 potato 5.8 orange 3.5 1.0 M HCl 0 milk of magnesia 10.5 urine 6.0 apple juice 3.8 detergents 8.0 - 9.0 bile 8.0 lemon juice 2.2 milk 6.4 tomato 4.2 ammonia 11.0 seawater 8.5 bleach 12.0 coffee 5.0 13 11 12 14 1 6 9 10 0 2 3 4 7 5 8 basic neutral acidic [H+] = [OH-] Timberlake, Chemistry 7th Edition, page 335
Calculating the pH • Since pH is dependent on the concentration of hydronium ions the formula for calculating pH is the following: pH = -log[H3O+] Example: Calculate pH if [H3O+] = 5.00 x 10-3M
Calculating Concentration of the Acids or Base from pH • [H3O+] = 10 –pH • EXAMPLE: pickle juice has a pH of 3.2 What is the hydronium ion concentration? • [H3O+] = 10 –3.2 • [H3O+] = 6.3 x 10 -4 M