pH and its measurement

1
pH and its measurement

• Section 4.5

2
Introduction

• pH is a common way to express acidity and basicity

Definition
pH is the Unit of Measure used to express the
degree of acidity of a substance.
pH - log H3O
3
In pure water H3O OH- 1 x 10 -7M
Therefore the pH of pure water is pH - log
H3O - log (1 x 10 -7)
pH 7
4
The pH scale
H3O gt OH-
H3O lt OH-
acidic
basic
H3O OH-
neutral
It is used to show the acidity of a soln.
5
Q1. What is the pH of HCl solution with H3O of
1 x 10 -2 M ?

• pH - log H3O
• - log (1 x 10 -2)

pH 2
6
Q2. If the pH of Diet Coke is 3.12, what
is the H3O ?

• pH - log H3O
• log H3O - pH
• Take antilog and get
• H3O 10-pH
• H3O 10-3.12
• H3O 7.6 x 10-4 M

7
Q3. What is the pH of the 0.001M NaOH
solution?
pH - log H3O - log (1 x 10 -11)
pH 11
Is this solution acidic or basic?
8
Methods
Measurement of pH
9
Experiment on measuring pH
lemon juice
vinegar
soap
baking soda
aspirin
household ammonia
10
Test the pH of most common solution - pH panel

• http//www.miamisci.org/ph/phpanel.html