1. Dr. Mohammed Golam RasulpH By
Dr. Mohammed Golam Rasul

2. السلام عليكم ورحمة الله وبركاته

3. بسم الله الرحمن الرحيم

4. Overview of Today’s lecture
1. Introduction to pH
2. pH scale
3. Importance of pH in Everyday Life
4. Testing the pH of Solutions
6.pH demonstration

5. Introduction
Living things have certain pH ranges for normal biochemical processes to occur.
pH is a logarithmic scale for measuring acids and bases.
Measured through indicators or pH meter.

6. What is pH?
The term "pH" is defined as the negative logarithm of H+ ion concentration of a given solution.
pH = -log10 [H+]

7. pH value
The pH value of a substance is directly related to the ratio of the hydrogen ion and hydroxyl ion concentrations.
If the H+ concentration is higher than OH- the material is acidic.
If the OH- concentration is higher than H+ the material is basic.
7 is neutral, < is acidic, >7 is basic

8. pH Scale The pH of a solution
is used to indicate the acidity of a solution
has values that usually range from 0 to 14
is acidic when the values are less than 7
is neutral with a pH of 7
is basic when the values are greater than 7

9. Strongest acid
Weak acid
Neutral
Weak Base
Strongest base

10. Importance of pH in Everyday Life
pH plays a very significant role in biochemical reactions. For example, the blood in our bodies is maintained at a pH value of
The stomach produces hydrochloric acid that helps in the digestion of food.
The bacteria present in the mouth act on sugar and food particles remaining in the mouth after eating to produce acids. The best way to prevent this is to clean the mouth after eating food or use toothpastes , which are generally basic, for cleaning the teeth so as to prevent tooth decay.

11. Learning Check
Identify each solution as A) acidic, B) basic, or N) neutral
___ 1) HCl with a pH = 1.5
___ 2) pancreatic fluid [H3O+] = 1 x 10−8 M
___ 3) Sprite soft drink, pH = 3.0
___ 4) pH = 7.0
___ 5) [OH−] = 3 x 10−10 M
___ 6) [H3O+ ] = 5 x 10−12 M

12. Solution Identify each solution as A) acidic, B) basic, or N) neutral
A 1) HCl with a pH = 1.5
B 2) Pancreatic fluid [H3O+] = 1 x 10−8 M
A 3) Sprite soft drink pH = 3.0
N 4) pH = 7.0
A 5) [OH-] = 3 x 10−10 M
B 6) [H3O+] = 5 x 10−12

13. Testing the pH of Solutions
The pH of solutions can be determined using
a pH meter
pH paper
indicators that have specific colors at different pH values

14. pH meter

15. pH paper
Measuring pH of various solutions using a pH paper
The pH paper is orange in color (before use) and changes color depending on the pH being tested. Look at the pH key to determine the pH of the solution ranging from 1-12.
A pH strip has been dipped into the solution and is displayed sitting outside the beaker

16. pH paper

17. pH paper

18. Indicators

19. SAFETY NO tasting, smelling, touching of liquids
NO tasting, smelling of papers
NO wandering – be aware while cleaning up.
First Aid – wash affected area with plenty of water.

20. Calculating pH
Mathematically, pH is the negative log of the hydronium ion concentration
pH = −log [H3O+]
For a solution with [H3O+] = 1 x 10−4,
pH = −log [1 x 10−4 ]
pH =[4.0]
pH = 4.0

21. Example of Calculating pH
Find the pH of a solution with a [H3O+] of 1.0 x 10−3.
STEP 1 Enter the [H3O+] value:
STEP 2 Press log key and change the sign:
log (1 x 10−3) = [3]
STEP 3 Make the number of digits after the decimal point (2) equal to the number of significant figures in the coefficient (2):
[H3O+] = 1.0 x 10−3 pH is 3.00

22. Learning Check 1) pH = 9.0 2) pH = 7.0 3) pH = 5.0
What is the pH of coffee if the [H3O+] is 1 x 10−5 M?
1) pH = 9.0
2) pH = 7.0
3) pH = 5.0

23. Solution What is the pH of coffee if the [H3O+] is 1 x 10−5 M?
STEP 1 Enter the [H3O+] value:
STEP 2 Press log key and change the sign:
log (1 x 10−5) = [5]
STEP 3 Make the number of digits after the decimal
point (1) equal to the number of significant figures in the coefficient (1):
[H3O+]= 1 x 10−5, pH is (3)

24. THANK YOU FOR YOUR ATTENTION