Chemical compounds can be classified into acids and bases based on the ability to furnish hydrogen or hydroxyl ions in an aqueous solution. Calculation of pH is a measure of the acidity or basicity, of a solution. The pH scale helps us to compare chemical compounds based on their ability to furnish H+ ions in solution. The pH value on the pH scale varies from 0-14. The chemical properties of a compound can be roughly predicted using the pH value. The calculation of pH is very crucial in chemistry. In this article, we look at the formula for calculating the pH of any solution.
pH values
- Solutions having a value of pH ranging from 0-7 are termed acidic substances.
- The values ranging from 7-14 on the pH scale is known as basic substances.
- Solutions having the value of pH equal to 0-7 on the pH scale are known as neutral solutions.
- Solutions having a value of pH equal to 0 are known as strongly acidic solutions
- whereas, solutions with a value of pH near 6-7 are known as weak acids.
Calculation of pH
pH is defined in terms of hydrogen ion concentration. But, in aqueous solutions, they are generally calculated in terms of the concentration of hydronium ions[H3O+]. pH has no units.
H+ + H2O –> H3O+ ——— Formation of hydronium ions in aqueous solutions
a pH of a compound can be calculated by the formula :
Where [H3O]+ is the concentration of hydronium ions in moles/liter.
Sample calculation of pH
Calculate the pH of sodium hydroxide solution having a hydronium concentration of 10-13 M.
pH = -log[10-13]
pH = 13
Calculate the pOH of sodium hydroxide solution having a hydroxyl concentration of 10-1M.
pH = -log[10-1]
pOH = 1
The pOH scale is similar to the pH scale, but it is defined in terms of hydroxyl ion concentration.
Importance of pH
- The changes in pH can make living difficult. For example, acid rain occurs when there is any change in the pH of water, which is less than 7. It affects both humans and aquatic life.
- Our mouth also produces acids from the bacteria present in it. They produce acids by degradation of food particles. The toothpaste which we use is basic which prevents the mouth from decaying.
- pH can also cause acidity problems when the stomach produces too much hydrochloric acid during indigestion. Hence, it is usually recommended to take antacids like magnesium hydroxide to increase the pH of the stomach.
- pH is also important for the activation of the enzyme pepsin, which helps in the digestion of proteins in food.
- When the pH of the mouth falls below 5.5, our teeth start decaying.
- Humans have a typical pH range from 7.35 to 7.45, which means their blood is very alkaline or normal.
See also
Dilute acids
Difference between acetic acid and glacial acetic acid
15 Properties of acids
15 Properties of bases
