NCERT Class X Science Class: Chapter –2. Acids, Bases and Salts – Part-7

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Question 36:

A student prepared solutions of (i) an acid and (ii) a base in two separate beakers. She forgot to label the solutions and litmus paper is not available in the laboratory. Since both the solutions are colorless, how will she distinguish between the two?

Answer:

Other than litmus paper there are more ways to distinguish between acids and bases-

(i) Using phenolphthalein indicator:

Put 2 drops of phenolphthalein in each beaker. The beaker containing base will turn pink and the beaker containing acid will remain colorless.

(ii) Using turmeric:

Put few drops from each beaker on turmeric powder. The base will turn turmeric to brick red and there will no colour change of turmeric by acid.

Question 37:

How would you distinguish between baking powder and washing soda by heating?

Answer:

The chemical formula of baking powder is sodium hydrogen carbonates whereas, that of washing soda is sodium carbonate

Sodium hydrogen carbonate on heating gives gas which will turn lime water milky whereas no such gas is obtained from sodium carbonate.

Question 38:

Salt A commonly used in bakery products on heating gets converted into another salt B which itself is used for removal of hardness of water and a gas C is evolved. The gas C when passed through lime water, turns it milky. Identify A, B and C.

Answer:

Baking powder , salt A is commonly used in bakery products. On heating it forms sodium carbonate B and gas, C is evolved. When gas is passed through lime water it forms calcium carbonate which is slightly soluble in water making it milky.

A —

B —

C —

Question 39:

In one of the industrial processes used for manufacture of sodium hydroxide, a gas X is formed as by product. The gas X reacts with lime water to give a compound Y which is used as a bleaching agent in chemical industry. Identify X and Y giving the chemical equation of the reactions involved.

Answer:

In the manufacture of sodium hydroxide, hydrogen gas and chlorine gas (X) are formed as by–products. When chlorine gas (X) reacts with lime water, it forms calcium oxychloride (bleaching powder) Y.

The reactions are

(Chlorine gas):

Calcium oxychloride (bleaching powder):

Question 40:

Fill in the missing data in the following table:

Name of the Salt and Formula (Q)
Name of the salt and Formula (Q)

S. No.

Name of the salt

Formula

Salt obtained from Base

Salt obtained from Acid

i.

Ammonium chloride

ii.

Copper sulphate

iii.

Sodium chloride

iv.

Magnesium nitrate

v.

Potassium sulphate

vi

Calcium nitrate

Answer:

Name of the Salt and Formula (A)
Name of the salt and Formula (A)

S. No.

Name of the salt

Formula

Salt obtained from Base

Salt obtained from Acid

i.

Ammonium chloride

ii.

Copper sulphate

iii.

Sodium chloride

iv.

Magnesium nitrate

v.

Potassium sulphate

vi

Calcium nitrate

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