NCERT Class X Science Class: Chapter –2. Acids, Bases and Salts – Part-9

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Question 44:

For making cake, baking powder is taken. If at home your mother uses baking soda instead of baking powder in cake,

  1. How will it affect the taste of the cake and why?

  2. How can baking soda be converted into baking powder?

  3. What is the role of tartaric acid added to baking soda?

Answer:

The chemical name of baking soda is sodium bicarbonate which gives sodium carbonate, carbon dioxide and water on heating. If baking soda is used instead of baking powder, in making of cake the formation of sodium carbonate would make the taste of cake bitter.

  1. By mixing of edible oil, usually tartaric acid, baking soda is converted into baking powder. Other mild edible oil is also used instead of tartaric acid.

  2. Tartaric acid gives hydrogen ion when water is added to it. Hydrogen ion produced by tartaric acid reacts with sodium bicarbonate and gives carbon dioxide which makes the dough soft and spongy. If sodium carbonate is formed because of heating, tartaric acid neutralizes it and forms sodium tartrate which has pleasant smell and good taste.

Question 45:

A metal carbonate X on reacting with an acid gives a gas which when passed through a solution Y gives the carbonate back. On the other hand, a gas G that is obtained at anode during electrolysis of brine is passed on dry Y, it gives a compound Z, used for disinfecting drinking water. Identity X, Y, G and Z.

Answer:

The gas evolved at anode during electrolysis of brine is chlorine (G)

When chlorine gas is passed through dry (Y) produces bleaching powder (Z) used for disinfecting drinking water.

Since Y and Z are calcium salts, therefore X is also a calcium salt and is calcium carbonate.

Question 46:

A dry pellet of a common base B, when kept in open absorbs moisture and turns sticky. The compound is also a by–product of chloralkali process. Identify B. What type of reaction occurs when B is treated with an acidic oxide? Write a balanced chemical equation for one such solution.

Answer:

Sodium hydroxide is a commonly used base and is hygroscopic, that is, it absorbs moisture from the atmosphere and becomes sticky.

The acidic oxides react with base to give salt and water. The reaction between and can be given as

Therefore, Common bas ‘B’ is sodium hydroxide. Reaction between ‘B’ and acidic oxide is neutralization reaction

Question 47:

A sulphate salt of Group 2 element of the Periodic Table is a white, soft substance, which can be molded into different shapes by making its dough. When this compound is left in open for some time, it becomes a solid mass and cannot be used for molding purposes. Identify the sulphate salt and why does it show such a behavior? Give the reaction involved.

Answer:

The substance which is used for making different shapes is Plaster of Paris. Its chemical name is calcium sulphate hemihydrate The two formula unit of share one molecule of water. As a result, it is soft.

When it is left open for some time, it absorbs moisture from the atmosphere and forms gypsum, which is a hard solid mass.

Question 48:

Identify the compound X on the basis of the reactions given below. Also, write the name and chemical formulae of A, B and C.

Image the Sodium hydroxide

Image the Sodium Hydroxide

Image the Sodium hydroxide

Answer:

Reaction of bases with metals :

1)

2)

3)

Therefore,