NCERT Class 10 Chapter 2 Acids Bases and Salts CBSE Board Sample Problems Long Answer (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question

A white powder is used by doctors to support fractured bones.

i) Write the name and chemical formula of powder.

ii) How is this prepared?

iii) When this white powder is mixed with water a hard solid mass is obtained. Write a balanced chemical equation for the change.

iv) Give one more use of this powder.

Solution

i) Plaster of Paris,

ii) It is prepared by heating gypsum to 373k

iii) On addition of water it sets into hard mass

iv) It is used for making sculpture, decorative items POP walls before painting.

Question

i) Write the name and chemical formula of calcium compound used as a disinfectant. How is this compound manufactured?

ii) Name the products obtained when sodium hydrogen carbonate is heated. Write the chemical equation for the reaction.

Solution

i) Bleaching Powder Chemical Formula: (Calcium Oxychloride)

Preparation: On passing chlorine gas through slaked lime bleaching powder is formed

ii) The products obtained are sodium carbonate, carbon dioxide and water

Question

In electrolysis of water,

a) Name the gas collected at cathode and anode.

b) Why is volume of gas collected at one electrode double than the other.

c) What would happen if dil. is not added to water?

Solution

a) The gas collected at cathode is hydrogen and gas collected at anode is oxygen.

b) The gas which is collected is double the amount during the electrolysis of water is hydrogen. This is because water contains two parts of hydrogen element as compared to one part of oxygen element by volume.

c) Pure water is a bad conductor of electricity which does not undergo electrolysis. On adding few drops of sulphuric acid it becomes good conductor of electricity due to which electrolysis takes place.

Question

1) Why does acidic solution conduct electricity?

2) Can basic solution conduct electricity?

3) Can separation of ions in acids take place when HCI is added to a non-aqueous solution?

4) While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?

Solution

Both acidic and basic solutions in water conduct electricity. Acids, when dissolved in water release the and bases when dissolved in water release the ions.

These ions are charged species and so act as charge carriers. In other words the conductivity of these solutions is due to the movement of these ions.

The process of dissolving an acid or a base in water is a highly exothermic one.

Care must be taken while mixing concentrated acid with water. The acid must always be added slowly to water with constant stirring. If water is added to a concentrated acid, the heat generated may cause the mixture to splash out and cause burns. The glass container may also break due to excessive local heating.

Question

Give suitable reasons for the following statements:

(i) Rain water conducts electricity but distilled water does not.

(ii) We feel burning sensation in the stomach when we over eat.

(iii) A tarnished copper vessel regains its shine when rubbed with lemon.

(iv) The crystals of washing soda change to white powder on exposure to air.

(y) An aqueous solution of sodium chloride is neutral but an aqueous solution of sodium carbonate is basic.

Solution

(i) Distilled water is a pure form of water, is neither acidic nor basic in nature. So distilled water does not dissociate into ions, since, conduction of electricity requires free ions so, distilled water does not conduct electricity. While rain water being an impure form of water, contains many ionic species. These ions are responsible for electrical conductivity of rain water.

(ii) Because when we over eat too much HCI is produced in our stomach which causes burning sensation.

(iii) Copper vessels tarnish is due to the formation of basic copper carbonate

which gets neutralized when rubbed with lemon and the copper vessel regains its shine.

(iv) Washing soda (sodium carbonate decahydrate) , when exposed to air, it loses 10 molecules of water and changes to white powder.

(y) Sodium chloride is a salt of strong acid HCI and strong base , so it is neutral. Sodium carbonate is a salt of weak acid and strong base NaOH, so it is basic.

Question

(i) Explain why is hydrochloric acid a strong acid and acetic acid, a weak acid. How can it be verified?

(ii) Explain why aqueous solution of an acid conducts electricity.

(iii) You have four solutions A, B, C and D. The pH of solution A is 6, B is 9, C is 12 and Dis7.

(a) Identify the most acidic and most basic solutions.

(b) Arrange the above four solutions in the increasing order of ion concentration.

(c) State the change in colour of pH paper on dipping in solution C and D.

Solution

(j) HCI will give rise to more ions and produces less ions on dissociation. The colour of pH paper depends on the concentration of ion. Colour becomes red for high concentration.

(ii) Aqueous solution of acids have which carry electric current through the solution.

(iii) (a) Most acidic: A and Most basic: C

(b)

(C) In C: blue, In D: green

Question

(a) A white compound Y of sodium is an active ingredient of antacids. Give the chemical name and common name of the compound Y. How is it manufactured? Give chemical equation.

(b) Write chemical equations to explain the manufacture of Washing soda from the compound Y. Write any two uses of washing soda.

Solution

(a) Sodium bi carbonate, Baking soda. It is prepared by Solvay process. It is used for the production of sodium bicarbonate and sodium carbonate industrially. In this process carbon dioxide, water, ammonia and brine solution in its concentrated form, are used as raw materials.

(b) Heat

Uses: Washing soda can be used as cleaning agent for domestic purposes.

It used to remove permanent hardness of water.

Question

(a) Equal lengths of Mg ribbon are taken in test tubes A and B. Hydrochloric acid added to test tube A. While acetic acid is added to test tube B. In which case the reaction would occur more vigorously and why? Write the chemical equations for reactions in test tube A and B.

(b) Why does Honey bee sting cause pain and irritation? Give a method to get relief from the discomfort

Solution

a) Reaction would occur more vigorously in sample A as HCI is a stronger acid than acetic acid

(b) The bee sting leaves an acid called formic acid in the body. Relief can be obtained by rubbing a mild base such as tooth paste or sodium bi carbonate (baking soda) on the affected area, as it is a mild base and neutralizes the affect of formic acid.

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