CBSE Class 10 Science Acids Bases and Salts Assignment Set A

MCQ Questions for NCERT Class 10 Science Acids Bases and Salts

Question. An aqueous solution with pH = 1 is
(a) strongly acidic
(b) strongly basic
(c) neutral
(d) weakly acidic

Answer : A

Question. Which of the following is(are) true when HCl (g) is passed through water ?
(i) It does not ionise in the solution as it is a covalent compound.
(ii) It ionises in the solution.
(iii) It gives both hydrogen and hydroxyl ion in the solution.
(iv) It forms hydronium ion in the solution due to the combination of hydrogen ion with water molecule.
(a) (i) only
(b) (iii) only
(c) (ii) and (iv)
(d) (iii) and (iv)

Answer : C

Question. Which among the following is not a base? 
(a) NaOH
(b) KOH
(c) NH₄OH
(d) C₂H₅OH

Answer : D

Question. What is the pH range of our body?
(a) 7.0 – 7.8
(b) 7.2 – 8.0
(c) 7.0 – 8.4
(d) 7.2 – 8.4

Answer : A

Question. During the preparation of hydrogen chloride gas on a humid day, the gas is usually passed through the guard tube containing calcium chloride. The role of calcium chloride taken in the guard tube is to 
(a) absorb the evolved gas
(b) moisten the gas
(c) absorb moisture from the gas
(d) absorb CL ions from the evolved gas

Answer : C

Question. Sodium hydroxide is used
(a) as an antacid
(b) in manufacture of soap
(c) as a cleansing agent
(d) in alkaline batteries

Answer : B

Question. Tomato is a natural source of which acid?
(a) Acetic acid
(b) Citric acid
(c) Tartaric acid
(d) Oxalic acid

Answer : D

Question. Which of the following statement is not correct? 
(a) All metal carbonates react with acid to give salt, water and carbon dioxide.
(b) All metal oxides react with water to give salt and acid.
(c) Some metals react with acids to give salt and hydrogen.
(d) Some non-metal oxides react with water to form an acid.

Answer : B

Question. How many water molecules does hydrated cal-cium sulphate contain?
(a) 5
(b) 10
(c) 7
(d) 2

Answer : D

Question. Which of the following phenomena occur, when a small amount of acid is added to water ?
(i) Ionisation
(ii) Neutralisation
(iii) Dilution
(iv) Formation
Choose the correct option from the following:
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (ii) and (iv)

Answer : C

Question. Which of the following salts does not contain water of crystallisation?
(a) Blue vitriol
(b) Baking soda
(c) Washing soda
(d) Gypsum

Answer : B

Question. At what temperature is gypsum heated to form Plaster of Paris?
(a) 90°C
(b) 100°C
(c) 110°C
(d) 120°C

Answer : B

Question. Which of the following is used for dissolution of gold ? 
(a) Hydrochloric acid
(b) Sulphuric acid
(c) Nitric acid
(d) Aqua regia

Answer : D

Question. NaOH is obtained by electrolysis of
(a) Aq. solution of NaCl
(b) Aq. Na₂CO₃
(c) Aq. NaHCO₃
(d) Molten NaCl

Answer : A

Question. Equal volumes of hydrochloric acid and sodium hydroxide solutions of same concentration are mixed and the pH of the resulting solution is checked with a pH paper. What would be the colour obtained?
(a) Red
(b) Yellow
(c) Yellowish green
(d) Blue

Answer : C

Question. Which of the following are present in a dilute aqueous solution of hydrochloric acid? 
(a) H₃O⁺ + Cl^–
(b) H₃O⁺ + OH^–
(c) Cl^– + OH^–
(d) unionised HCl

Answer : A

Question. Which one of the following can be used as an acid-base indicator by a visually impared (blind) student ?
(a) Litmus
(b) Turmeric
(c) Vanilla essence
(d) Petunia leaves

Answer : C

Question. NaHCO, formed by reaction of
(a) NaOH + H₂CO₃
(b) NaCl + H₂CO₃
(c) Na₂CO₃ + HCl
(d) NaOH + Na₂CO₃

Answer : A

Question. Which of the following statements is true for acids?
(a) Bitter and change red litmus to blue.
(b) Sour and change red litmus to blue.
(c) Sour and change blue litmus to red.
(d) Bitter and change blue litmus to red.

Answer : C

Question. An aqueous solution turns red litmus solution blue. Excess addition of which of the following solution would reverse the change? 
(a) Baking power
(b) Lime
(c) Ammonium hydroxide solution
(d) Hydrochloric acid

Answer : D

Question. pH of H₂0 is
(a) 7
(b) 8
(c) 9
(d) 10

Answer : A

Question. Ag₂S reacts with H₂SO₄ to form
(a) AgSO₄
(b) Ag₂SO₄ + H₂S
(c)Ag₂O + H₂S
(d) AgOH + H₂S

Answer : B

Question. Lime water reacts with chlorine to form
(a) CaCl₂
(b) CaOCl₂
(c) Ca(ClO₃)₂
(d) CaO₂Cl₂

Answer : B

Question. In an attempt to demonstrate electrical conductivity through an electrolyte, the following apparatus was set up.
Which among the following statement)s) is (are) correct?
(i) Bulb will not glow because electrolyte is not acidic.
(ii) Bulb will glow because NaOH is a strong base and furnishes ions for conduction.
(iii) Bulb will not glow because circuit is incomplete.
(iv) Bulb will not glow because it depends upon the type of electrolytic solution.
(a) (i) and (iii)
(b) (ii) and (iv)
(c) (ii) only
(d) (iv) only

Answer : C

Question : What is baking powder? How does it make the cake soft and spongy?
Answer :  Baking powder is a mixture of sodium hydrogen carbonate and tartaric acid On heating it liberates CO₂ which makes the cake soft and spongy

Question : Write the chemical name and formula of the compound which is used as an antacid.
Answer :  Sodium bicarbonate, NaHCO₃ 

Question :  a) A milk man adds a very small amount of baking soda to fresh milk. Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
b) Mention pH range within which our bodyworks?
c) Explain how antacids give relief from acidity.
d) Mention the nature of tooth pastes. How do they prevent tooth decay?
Answer :  a) It is done to prevent the formation of lactic acid which spoils the milk
b) pH range 7.0- 7.8
c) Antacids neutralizes excess of acid in our body and gives relief.
d) Basic) Neutralize the acid formed in the mouth

Question : A gas X reacts with lime water and forms a compound Y which is used as bleaching agent in the chemical industry. Identify X and Y. Give the chemical equation of the reaction involved)
Answer :  X is chlorine Y is CaOCl₂ (calcium oxy chloride) used as bleaching agent.
        Ca (OH)₂+ Cl₂—–→ CaOCl₂ +H₂O 

Question : Plaster of Paris should be stored in a moisture-proof container. Explain why? 

Answer :  Plaster of Paris should be stored in a moisture-proof container, because in presence of moisture, plaster of paris sets to give a hard mass.

It can be no longer used for making moulds and statues. To avoid above reaction to occur Plaster of Paris be stored in moisture- proof containers.

 

Question : How is plaster of Paris prepared ? Why is temperature control necessary during its preparation ? How does it react with water ? 

Answer : Plaster of paris is prepared from gypsum.

Gypsum is calcium sulphate dihydrate. The chemical formula of gypsum is CaSO₄·2H₂O

Plaster of paris is prepared by heating gypsum to a temperature of 373K.When gypsum is heated to a temperature of 373k ,It loses three-Fourths of its water of crystallisation and forms plaster of paris.

 

It may be noted the temperature should be controlled carefully. It should not be allowed to rise above 425 K, because the whole of water is lost and anhydrous calcium sulphate (CaSO₄) is produced. It is called dead burnt plaster. It has not such property as that of plaster of paris.

When mixed with water, it forms a paste which sets into a hard mass. This is called setting of Plaster of Paris. The setting of Plaster of Paris is due to its hydration into gypsum.

(CaSO₄)₂.H₂O + 3H₂O → CaSO₄.2H₂O

Plaster of paris Gypsum