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How strong are Acid or Base solutions?
A scale for measuring hydrogen ion concentration in a solution is called pH scale. The ‘p’ in pH stands for ‘potenz’ in German meaning power. pH scale is a set of numbers from 0 to 14 which is used to indicate whether a solution is acidic, basic or neutral.
· Acids have pH less than 7
· Bases have pH greater than 7
· A neutral solution has pH equal to 7
The pH of a solution can be determined by using a universal indicator. It contains a mixture of dyes. It comes in the form of a solution or pH paper.
A more common method of measuring pH in a school laboratory is by using pH paper. pH paper contains a mixture of indicator.
Are plants and animals pH sensitive? Our body works within the pH range of 7.0 to 7.8. Living organisms can survive only in narrow range of pH change.
It is very interesting to note that our stomach produces hydrochloric acid. It helps in the digestion of food without harming the stomach. During indigestion the stomach produces too much acid and this causes pain and irritation. pH of stomach uid is approximately 2.0.
White enamel coating of our teeth is calcium phosphate, the hardest substance in our body. Toothpastes which are generally basic and used for cleaning the teeth can neutralise the excess acid and prevent tooth decay.
In agriculture, the pH of soil is very important. Citrus fruits require slightly alkaline soil, while rice requires acidic soil and sugarcane requires neutral soil.
The pH of rain water is approximately 7 which means that it is neutral and also represents its high purity. If the atmospheric air is polluted with oxide gases of sulphur and nitrogen, they get dissolved in rainwater and make its pH less than 7. Thus, if the pH of rain water is less than 7, then it is called acid rain. When acid rain flows into the rivers it lowers the pH of the river water. The survival of aquatic life in such rivers becomes difficult.
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