Strength of Acidic or Basic Solutions



  • pH Scale
  • Importance of pH in Everyday Life


1. In our digestive system, Hydrochloric acid produced in our stomach helps the digestion of food without causing any harm to the stomach. But when the amount of the acid exceeds a specific limit due to indigestion, pain and irritation are created in the stomach. So, to neutralise the effect of excess acid, a mild base called antacid is usually taken. Magnesium hydroxide (milk of magnesia) is a mild base usually used as an antacid.

2. Acids cause tooth decay. When we eat sugary food, it gets degraded by bacteria present in the mouth, and an acid is formed. When the pH becomes lower than 5.5, tooth enamel gets corroded. Saliva, which is slightly alkaline, produced in the mouth neutralizes some acid, but excess acid remains unaffected. The excess acid can be removed only by the use of toothpaste which is alkaline. Neem stick contains alkaline juice. So, cleaning the tooth with a Neem stick also helps reduce tooth decay.

3. Acid is produced in fatigued muscles. Due to physical exercise, stiffness and pain in the muscle start due to the formation of lactic acid. The supply of oxygen in the muscle is reduced. This causes difficulty in releasing energy, leading to an increase in the rate of anaerobic metabolism. As a result, lactic acid gets accumulated in the muscles.

4. Some animals and plants contain acids. Honeybee injects an acid through its stings which causes pain and irritation. Hence, a mild base like baking soda is applied to treat the wound. Similarly, nettle leaves, which have stinging hairs, inject formic acid into our bodies when touched. This causes a burning pain.
Note: Nettle is a stinging plant. When one accidentally touches its hair, a painful effect is produced. As a remedy, the affected area is rubbed with the dock plant. The dock plant is alkaline, which neutralises the effect of the acid.

5. The brilliance of a tarnished copper vessel can be restored by using acid. You know, lemon juice contains an acid. We rub a copper vessel with a piece of lemon to clean it. The formation of a layer of basic copper oxide causes the tarnish on the vessel. Since lemon juice contains citric acid, it reacts with copper oxide to form copper citrate and is washed away. The vessel then regains its shining appearance.

6. pH of the soil. Soil is generally acidic. Plants require a definite pH range for their proper growth. They do not grow in alkaline soil. Many plants do not grow properly in highly acidic or highly alkaline soil. So, highly acidic soil is treated by spreading quicklime, slaked lime or calcium carbonate to lower acidity.


In pH scale ‘p’ stands for ‘potenz’. Potenz is a German word which means ‘power’ or ‘potential’. Here; ‘H’ stands for hydrogen ion. Thus, pH means the potential of hydrogen or power of hydrogen.

The strength of acid or base depends upon the hydrogen ion concentration. If the concentration of hydrogen ion is greater than hydroxide ion, the solution is called acidic. If the concentration of hydrogen ion is smaller than the hydroxide ion, the solution is called basic. If the concentration of hydrogen ion is equal to the concentration of hydroxide ion, the solution is called neutral solution.

pH is a measure of hydrogen ion concentration a measure of the acidity or alkalinity of a solution.

The pH scale usually ranges from 0 to 14. Aqueous solution at 25°C with a pH less than 7 are acidic while those with a pH greater than 7 are basic or alkaline. A pH level of 7.0 at 25°C is defined as ‘Neutral’

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Video Tutorials

We have provided more than 1 series of video tutorials for some topics to help you get a better understanding of the topic.

Series 1

Series 2

Series 3 | Acid & Base part 13 (Ph : How strong are acid & base)

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Acid & Base part 13 (Ph : How strong are acid & base) [00:14:32]
Series: series 1


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