Wednesday, 26 September 2018

NCERT solution class 7 science ch 5 acids bases and salts.

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ncert sulution class 7 ch 5.

Here solution of science book of class 7 ch 5 .detailed solutions of ncert book of class 7.

questions 1 to 5.

Q 1.State the differences between acids and bases.
Answer:
Acid:- (i) these are sour to taste.
(ii) acid turn blue litmus red.
(iii) acid do not change colour red litmus paper.
Bases:-(I) these are bitter to taste.
(ii) bases turn red litmus blue.
(iii) bases do not change colour blue litmus paper.

Q 2.ammonia isfound in many household product,such as window cleaner. It turn red litmus blue. What is its nature?
Answer:Ammonia is fundamental in nature because it turns the colors of red litmus paper into blue.

Q 3.Name the sources from which litmus solution is obtained.what is the use of this solution?
Answer:Litmus solution is obtained from Lifes. To get the solution from the solution, the natural dye extracted in distilled water is dissolved in distilled water. It is used as an indicator to differentiate between acids and bases.
       Solution.                 Colour of litmus solution
(i) acidic-----------.  Red
(ii) basic----------- Blue
(iii) neutral------- no change

Q 4.i s the distilled water acidic/basic/neutral? How would you verify it?
Answer:Distilled water is neutral in nature. It can be verified using red and blue litmus paper. Neither will the color change with distilled water. This proves that the distilled water is neutral.

Q 5.Describe the proces of neutralization with the help of an example.
Answer:The reaction between an acid and the base is known as neutral reaction.In this reaction,both acid and base cancel each other's effect. Neutrality and neutral reaction results in the formation of water. During this reaction, energy is in the form of heat
has developed.
Acid+Base→Salt+Water+Heat
For exampl, when sodium hydroxide (NaOH) is added to hydrochloric acid (HCl), sodium chloride (NaCl) and water (H2O) are obtained.


questions 6 to 11.

Q 6.mark T in true statement and F for false statement.
Only answer :
(i) f
(ii) f
(iii) t
(iv) t
(v) f

Q 7.share the drinks are........
Answer:Since drinks are food, therefore, Dorjee can make a decision by tasting the drink. Acidic drink will be sour to taste while the basic drink will be bitter to taste and there will be no taste of neutral drink.
If Dorjee has litmus indicator (solution or paper), then it can help. He should put a drop of each drink on blue litmus paper. If the color of litmus paper becomes red, then it is an acidic beverage. Some of the remaining drinks are acidic and some are neutral. Then, he should put a drop of remaining beverage on the red litmus paper. If the color turns to blue, then it is original and the other is neutral. In this way, he can present his related drink to all his three customers.

Q 8.explain why:-
(a)an    antacid tablet is taken when you suffer from acidity.
Answer:This is because during acidity, there is excess production of acid in the stomach. There is a base in an antacid, such as the milk of magnesia. These figures react more than acid and neutralize their effect, thus giving us relief.

(b)Calamine solution is applied on the skin when an ant bites.
Answer:Whenan ant bites, it injects formic acid into the skin. The calamine solution contains zinc carbonate which is fundamental in nature. Therefore, it applies to the skin to neutralize the effect of formic acid.

(c)Factory wast is neutralised before disposing it into the water bodies.
Answer:The waste of the factory is acid. Therefore, these waste, when directly drained water bodies, harm the aquatic life. Therefore, these wastes are neutralized with basic chemicals before disposing of water bodies.

Q 9.Three liquid are given to you.one   is hydrochloric acid,another is sodium hydroxide and the third is a sugar solution. 
How will you identify them? You have only turmeric indicator.
Answer:We will put a drop each of  solution on each hydrochloric acid, sodium hydroxide, and turmeric indicators. The fluid which changes the color of turmeric indicator to red is root in nature, i.e. sodium hydroxide





Now, we will keep the drop of sodium hydroxide separately on a drop of two different liquids. After this, we will put the drops of these blends on the turmeric indicator. The drop that turns the color of the turmeric indicator into red, there is a Chinese solution. This is because the mix of basic and neutral solutions is fundamental in nature. On the other hand, the drop which will not change the color of the turmeric indicator, it contains hydrochloric acid. This is because hydrochloric acid reacts with sodium hydroxide to form a neutral solution.



Q 10.Bluelitmus paper is dipped in a solution. It remain blue. What is the nature of the solution? Explain.
Answer:We know that basic and neutral solutions do not change the color of blue litmus paper. Since the blue litmus remains blue after the dip in the solution, the solution is original or neutral in nature.
Puta drop of this solution on a red litmus paper. If it turns blue, then the above solution is original in nature and if there is no color change, then it is neutral.

Q 11.Consider the following statement:
Answer:(iv) only d. Is correct.

The end chapter...
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