pH and Indicators

Chemistry

Mrs. Coyle

Basic14>ph>7

Neutral

ph=7

Acidic 1<pH<7

Self Ionization of H2O

H2O H+ (aq) + OH- (aq)

Ion Product Constant K w for Water:

Kw= [H+ ] x [OH-] =1.0 x 10 -14

For pure H2O

[H+ ] = [OH-] = 1.0 x 10-7M

pH

• 1909 Soren Sorensen (Danish)

pH=-log[H+]

What is the pH of pure water?

Ex 1: Find the pH for [H+]=10-3M

• Answer: pH=3

Ex 2: Find the pH for [H+]=5x10-3M

• Answer: pH=2.3

Finding [H+] from pH

• [H+]= 10-pH

Ex 3: Find the [H+] for pH=5

• Answer: [H+] = 10-5 M

Ex 4: Find the [H+] for pH=5.8

• [H+]= 10-pH

• Answer: [H+] = 1.6x10-6 M

pOH

pH=-log[H+]

pH + pOH=14

Basic(Alkaline)Solutions

Acidic Solutions

Neutral Solutions

Acids

Change phenolphthalein to colorless.

Acids

• Turn litmus paper from blue to red.

Bases

Change phenolphthalein to pink.