The pH scale measures how acidic or basic a solution is on a scale from 0-14, with 0-7 being acidic and 7-14 being basic/alkaline. The pH is defined as the negative log of the hydrogen ion concentration. A pH of 7 indicates a neutral substance, like water. Examples show how to calculate the pH from given hydrogen ion concentrations using the logarithmic definition of pH.

1. pH scale
Objective :
Explain and use the pH scale.

2. What is the pH scale?
– The pH scale measures how acidic or basic a
solution is.

3. The pH scale
– The pH scale is the concentration of hydrogen ions in a given
substance.
 
 HpH log
How cacn we calculate the PH:

4. Test Your Knowledge
– What is the range of an ACID on the pH scale?
Ans: 0-7
– What is the range of a BASE and what is another name for
a BASE?
Ans: 7-14, Alkaline

5. Did we Miss
something??
– What happens when the pH of a substance is 7?
– Ans: A pH level of 7 indicates a Neutral Substance
i.e: Water!

6. Calculating the pH
pH = - log [H+]
(Remember that the [ ] mean Molarity)
•pH = - (- 10)
•pH = 10
Example: If [H+] = 1 X 10-10
pH = - log 1 X 10-10
•pH = - (- 4.74)
•pH = 4.74
Example: If [H+] = 1.8 X 10-5
pH = - log 1.8 X 10-5

7. Try These!
FIND THE PH OF THESE: 1) A 0.15 M SOLUTION OF
HYDROCHLORIC ACID
[H+] = 0.15
2) A 3.00 X 10-7 M
SOLUTION OF NITRIC ACID
[H+] = 3.00 X 10-7

8. pH of Common Substances

9. Why we Learn about Acids & Bases?
– The pH of a swimming pool must be checked periodically. Why?
– Is it important for Lakes & Rivers to maintain a certain pH?