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CLASS - 10 SCIENCE IMPORTANT QUESTIONS OF MARK 3   FOR BOARD EXAMINATION

QUESTION NO. 6

Why is respiration considered an exothermic reaction ? Explain.

ANSWER NO. 6

During digestion, food is broken down into simpler substance. Carbohydrates are broken down to form glucose. This glucose combines with oxygen in the cell of our body and provides energy. The special name of this reaction is respiration.

QUESTION NO. 7

Write the importance of PH in everyday life.

ANSWER NO. 7

1. Our digestive system - Hydrochloric acid produced in our stomach helps the digestion of food. But when the amount of acid goes beyond a certain limit you to  indigestion, pain and irritation are created. To neutralize if that of excess acid magnesium Hydroxide (milk of magnesia) is a my base used as antacid.

 2. Acid cause tooth decay : Tooth decay starts when the pH of mouth is lower than 5.5. The best way to prevent this clean the mouth after eating.

3. To determine the pH value of river, because living organism can survive in a narrow range of PH change.

 4. Plants required a specific pH range for their healthy growth.

 5. Animals used acid for their protection which causes pain and irritation use of mild base light baking soda on stung part given relief.

QUESTION NO. 8

Write the chemical equation to produce the bleaching powder and write its uses.

ANSWER NO. 8


The chlorine gas is used for the manufacture for men of bleaching powder. Bleaching powder is produced by the action of chlorine on dry slaked lime. (Ca(OH)2).
      Ca(OH)2 + Cl2 -------------> CaOCl2+H2O

USES OF BLEACHING POWDER :
1. Bleaching cotton and lining in the textile industry, paper industry and it is also used in laundry.

 2. In many chemical industry it is used as oxidizing agent.

 3. It act as antigerm for drinking water.

QUESTION NO. 9


A white powder is added while baking cakes to make it soft and spongy. Name main ingredients.  Explain the function of each ingredient. Write the chemical reaction taking place when the Powder is heated during baking.

ANSWER NO. 9


Name of compound is sodium hydrogen carbonate (NaHCO3).
       The common name is baking soda. It is commonly used in kitchen for making tasty crispy pakoras.

   2NaHCO3 -----------------------> Na2CO3 + H2O + CO2

 1. Carbon dioxide produced during their reaction can cause bread or cake to rise making them soft and spongy.
2. Sodium hydrogen carbonate is also an ingredient in antacid. Being alkaline, it neutralize excess of in stomach and provide relief.
3. It is also used in Soda acid fire extinguisher.

QUESTION NO. 10


With a labelled diagram describe in brief an activity to show the formation of an Easter.

ANSWER NO. 10



1. Take one ml ethanol (absolute alcohol) and 1 ml glacial Acetic Acid along with few drops of concentrated sulphuric acid in a test tube.
2. Warm this mixture in water but for at least five minutes.
3. Pour into a beaker containing 20 to 50 ml of water and smell the result mixture. This is the formation of Easter.

 ALSO SEE IMPORTANT QUESTIONS OF 3 MARK

 From question no. 1 to 5

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