Study Materials

NCERT Solutions for Class 7th Science


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Chapter 5. Acids, Bases and Salts

Additional Questions with Solutions




Ques: What are acids?
Ans: Acids are sour substances which are found in curd, lemon juice, and orange juice and in vinegar. 

Ques: What are base?
Ans: Substances like these which are bitter in taste and feel soapy on touching are known as bases. EX- baking soda, soap and milk of magnesia. 

Ques: Write the name of five such substances which are acidic in nature. 
Ans: curd, lemon juice, orange juice, tomato and vinegar etc. 

Ques: What is called the object which is used to identify the acids and bases? 
Ans: Indicator. 

Ques: Name a natural indicator?
Ans: Litmus paper. 

Ques: Write the type of litmus paper?
Ans: There are two types of litmus paper. 

(i) Red litmus paper 

(ii) Blue litmus paper 

Ques: From where does litmus paper obtain?
Ans: Litmus paper obtains from lichen plants. 

Ques: What is litmus paper?
Ans: Litmus paper is a natural indicator which is used to identify the acids and bases. 

Ques: What is indicator?
Ans: A special kind of substances are used to identify the acids and bases, these are called indicator. 

Ques: Which acid is found in vinegar?
Ans: Acetic acid. 

Ques: Which acid is found in ant’s sting?
Ans: Formic acid. 

Ques: Name the acid which is found in curd?
Ans: Lactic acid. 

Ques: What is called the neutralised solution?
Ans: Such a solution which does not change the colour of red and blue litmus paper is called neutralised solution. 

Ques: What is neutralisation?
Ans: Such a reaction in which acid and base nutralise the effect of each other is known as neutralization.

Ques: Write the difference between acid and base.


(i) Acids are sour in taste.

(ii) It turns blue litmus into red.

(iii) Example: Hydrochloric acid. 


(i) Bases are bitter in taste.

(ii) It turns red litmus into blue. 

(iii) Example: Sodium hydroxide.

Ques: Why is dissolved baking soda applied on ant’s or scorpion’s sting?
Ans: There is a special kind of acid is found in the sting of ant and scorpion. So to neutralise the acid there is applied dissolved baking soda. 

Ques: What is indigestion?
Ans: The food does not digest properly in our stomach due to excess of hydrochloric acid (acidity) this is known as indigestion. 

Ques: What should we take to remove the indigestion?
Ans: We should take antacid like milk of magnesia to remove the indigestion. 

Ques: What is salt?
Ans: A new substance is produced in neutralisation reaction is known as salt. 

Ques: Write the nature of salt.
Ans: neutral. 
Ques: Why should it be taken great care while handling acid and base in laboratory? 
Ans: Great care should be taken while handling laboratory acids and bases because these are corrosive in nature, irritating and harmful to skin.
Ques: Name a synthetic indicator. 
Ans: Phenolphthalein.
Ques: What happens when acid and base react to each other? Write the equation for this.
Ans: When acid and base react to each other these give salt and water.
Acid + base -----> salt + water. 
Hydrochloric acid (HCl) + Sodium hydroxide (NaOH) -----> Sodium chloride (NaCl) + Water (H2O)
Ques: What is soil treatment? How is soil treated? 
Ans: When soil becomes too acidic or too basic, it is treated by using some acid or base substances. This is called soil treatment. When the soil is too acidic, it is treated with bases like quick lime (calcium oxide) or slaked lime (calcium hydroxide). If the soil is basic, organic matter is added to it. Organic matter releases acids which neutralises the basic nature of the soil.
Ques: How the factory wastages are harmful for aquatic animals?
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.


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