Goals to Accomplish Today 5.18.12

1.Go over pg. 74-75 and concept review

2.Lecture: Indicators and pH

(A) pg. 76-77

Universal Indicator

Base

s

Acid

s

Phenolpthalein IndicatorIdentifies if a base is present: turns

pink

Litmus Paper- tells you if you have an acid or a base

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 Neutral8-14 Basic

Measures the hydronium ions in a solutionThe more hydronium ion the more acidic

pH paper

pH scale : measures acidity/basicity

pH scale

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

ACID BASE

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)

: measures acidity/basicity

10x10x10x

Soren Sorensen(1868 - 1939)

pH scale`

pH of Common Substances

Timberlake, Chemistry 7th Edition, page 335

1.0 MHCl0

gastricjuice1.6

vinegar2.8

carbonated beverage3.0

orange3.5

apple juice3.8

tomato4.2

lemonjuice2.2 coffee

5.0

bread5.5

soil5.5

potato5.8

urine6.0

milk6.4

water (pure)7.0

drinking water7.2

blood7.4

detergents8.0 - 9.0

bile8.0

seawater8.5

milk of magnesia10.5

ammonia11.0

bleach12.0

1.0 MNaOH(lye)14.0

8 9 10 11 12 14133 4 5 621 70

acidic neutral basic[H+] = [OH-]

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