Ans. Acids - Curd, lemon juice, vinegar, orange juice etc.
Base - baking soda, lime water etc.
Ans. Solutions of substances that show different colour in acidic, basic and neutral solutions are called indicators.
Ans. China rose indicator turns acidic solutions to dark pink (magenta) and basic solutions to green.
Ans. Ammonia is basic in nature as it turns the red litmus blue.
Ans. A turmeric stain on my white shirt is turned to red when it is washed with soap because the soap solution is basic in nature.
Ans. To prepare limewater, dissolve some lime (chuna) in water in a bottle. Stir the solution and keep it for some time. Pour a little from the top. This is lime water.
Ans. The solution could be a base or neutral solution because blue litmus paper doesn’t change its colour in the neutral as well as in basic solution.
Ans. The solutions which do not change the colour of either red or blue litmus are known as neutral solutions. Examples- sugar solution, distilled water, salt etc.
Ans. Distilled water is neutral in nature. This can be verified by using red and blue litmus papers. Neither will show change in colour with distilled water. This proves that distilled water is neutral.
Ans. The rain becomes acidic because carbon dioxide, sulphur dioxide and nitrogen dioxide (which are released into the air as pollutants) dissolve in rain drops to form carbonic acid, sulphuric acid and nitric acid respectively.
Ans. The wastes of many factories contain acids. If they are allowed to flow into the water bodies, the acids will kill fish and other organisms. The factory wastes are, therefore, neutralised by adding basic substances.
Ans. When an ant bites, it injects the acidic liquid (formic acid) into the skin. The effect of the acid can be neutralised by rubbing moist baking soda (sodium hydrogen carbonate) or calamine solution, which contains zinc carbonate.
Ans. Litmus solution is extracted from lichens. It is most commonly used natural indicator. It has a mauve (purple) colour in distilled water. When added to an acidic solution, it turns red and when added to a basic solution, it turns blue.
Ans. Our stomach contains hydrochloric acid. It helps us to digest food. But too much of acid in the stomach causes indigestion. Sometimes indigestion is painful. To relieve indigestion, we take an antacid such as milk of magnesia, which contains magnesium hydroxide. It neutralises the effect of excessive acid.
Ans. The reaction between an acid and a base is known as neutralisation. Salt and water are produced in this process with the evolution of heat.
Acid+Base → Salt+Water
(Heat is evolved)
The following reaction is an example:
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