Strength of Acid Base solution: pH Scale
pH is defined as the negative logarithms of H+ ion concentrations here the meaning of the pH is justified as power of hydrogen.
pH= – log10[H+]
In 1909 Sorensen developed a scale ( know as pH Scale) on which the strength of acid solutions as well as basic solution could be represented by making use of hydrogen ion concentrations in them.
pH= – log10[H+]
- Acidic solution have excess of hydrogen ion [H+] and the basic solution have hydroxide ion [OH-] .
- The pH of solution is inversely proportional to the concentrations of hydrogen ion in it.
- Higher the hydronium ion concentrations present in the solution lower its pH value .
- The pH Scale has the value from 0 to 14.
- It scales used for measuring hydrogen ion concentrations .
- For acidic solution pH is <7
- For basic solution pH is >7
- For neutral solution pH = 7
Example : 1) calculate the pH of 0.1 M of HCl?
pH= – log10[H+]
pH= – log10[0.1]:. – log10= 1
pH = 1
2) Calculate the pH of 10-2 M HCl?
pH= – log10[H+]
pH= – log10[1010-2]
pH = 2
3) Calculate the pH of 0.1 M of NaOH?
pOH= – log10[OH-]
= – log10[0.1]
pOH = 1
So , pH + pOH= 14
pH+ 1 = 14
pH = 14- 1
pH= 13 ( because NaOH is base)
Approximately pH value for some common solution:
Solution | Approximate pH | Solution | Approximate pH |
Gastric juice | 1.0-3.0 | Pure water | 7.0 |
Lemon juice | 2.2-2.4 | Blood | 7.3-7.4 |
Vinegar | 3.0 | Baking soda | 8.4 |
Tomato juice | 4.1 | Sea water | 9.0 |
Acid rain | 5.6 | Washing soda | 10.5 |
Milk | 6.5 | Sodium hydroxide | 14.0 |
Question answer
1) What is pH?
2) Who developed the pH Scale explain?
3) Explain the pH Scale of acidic basic and neutral solution?
4) Calculate the pH of 10-3M HCl?
What is Universal indicator
I don’t know