CBSE Class 10 Science Acids Bases and Salts Assignment Set A

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

Question : Which of the following is a double salt ? 
(A) Blue Vitriol
(B) Glauber’s salt
(C) Potash Alum
(D) Potassium Ferrocyanide
Answer : C

Question : The reagent obtained by dissolving Copper sulphate in aqueous solution of Citric acid and Sodium carbonate is...................
(A) Bayer’s reagent
(B) Tollen’s reagent
(C) Fehling reagent
(D) Benedict reagent
Answer : D

Question : When Sodium carbonate (Na₂CO₃) reacts with Silica (SiO₂) gives.................
(A) Soda Glass
(B) Water glass
(C) Crook’s glass
(D) Pyrex glass
Answer : B

Question : In order to decrease the role of setting of Cement, which compound is mixed in it ?
(A) Ca(OH)₂ (Slaked lime)
(B) CaCO₃ (Calcium Carbonate)
(C) CaSO₄.2H₂O (Gypsum)
(D) Al₂O₃ (Alumina)
Answer : C

Question : Which one of the following is not base ? 
(A) B(OH)₃
(B) KOH
(C) Ca(OH)₂
(D) NH₄OH
Answer : A

Question : The nature of solution when sodium carbonate is dissolved in water will be
(A) acidic
(B) basic
(C) neutral
(D) amphoteric
Answer : B

Question : pH of a solution is zero. The nature of this solution is 
(A) acidic
(B) basic
(C) neutral
(D) amphoteric
Answer : A

Question : The difference in number of crystalline water molecules in a molecule of gypsum and a molecule of plaster of Paris is 
(A) 5/2
(B) 2
(C) 1/2
(D) 3/2
Answer : D

Question : Match the following : 
(a) formic acid            (i) dehydrating agent
(b) Nitric acid             (ii) organic acid
(c) Electrolyte            (iii) Mineral acid
(d) Conc. H₂SO₄        (iv) Nacl
(A) (a) (ii), (b) (iii), (c) (iv), (d) (i)
(B) (a) (i), (b)(ii), (c) (iii), (d) (iv)
(C) (a) (iii), (b)(i), (c) (iv), (d) (ii)
(D) (a) (iv), (b)(iii), (c) (i), (d) (ii)
Answer : A

Question : A milkman added a small pinch of baking soda of fresh milk which has pH close to 6. As a result, pH of the medium
(A) became close to 2
(B) became close to 4
(C) did not undergo any changes
(D) became close to 8
Answer : D

Question : Which of the following salts does not contain any water of crystallisation ?
(A) blue vitriol
(B) washing soda
(C) baking Soda
(D) gypsum
Answer : C

Question : The substance which is chemically resistant and can hold aqua regia
(A) Ceramics
(B) Glass
(C) Fibre
(D) Thermosetting plastic
Answer : B

Question : Skin becomes yellow in conc. HNO₃ as 
(A) HNO₃ acts as an oxidizing agent
(B) HNO₂ acts as a dehydrating agent
(C) Nitro-cellulose is formed
(D) The proteins are converted into xantho proteins
Answer : A

Question : Match the items of column I with the items of column II 
Column – I (Polymers)       Column – II
a. aq. NaCl solution           i. Acidic
b. aq. Na2CO3 solution     ii. Basic
c. aq. NH₄Cl solution        iii. Neutral
d. aq. CaO solution           iv. Amphoteric
(A) c-i, d-iii, b-ii, a-i
(B) d-i, b-iv, a-iii c-iv
(C) a-iii, b-ii, c-i, d-iii
(D) b-ii, a-iii, d-ii, c-i
Answer : D

Question : The pH of pure water at 25°C is 7. If water is heated to boil, then 
(A) pH will decrease and water will become acidic
(B) pH will increase and water will become basic
(C) pH will decrease but water will remain natural
(D) pH will remain 7
Answer : C

Question : Which of the following is pH of basic solution ?
(A) 7
(B) 4.2
(C) 6.9
(D) 10.2
Answer : B

Question : Which reagent is able to dissolve gold and platinum ? 
(A) Nitric acid
(B) Aqua-regia
(C) Hydrochloric acid
(D) Sulphuric acid.
Answer : B

Question : The conjugate base of H₂PO₄^– is : 
(A) PO₄^3–
(B) P₂O₅
(C) H₃PO₄
(D) HPO₄^2–
Answer : D

Question : What is the conjugate base of OH^– ? 
(A) O₂
(B) H₂O
(C) O^–
(D) O^2–
Answer : D

Question : Hydrogen ion concentration in mol/L in a solution of pH = 5.4 will be :
(A) 3.98 × 10⁸
(B) 3.88 × 10⁶
(C) 3.68 × 10^–6
(D) 3.98 × 10^–6
Answer : D

Question :Three reactions involving H₂PO₄^– are given below :
(i) H₃PO₄ + H₂O → H₃O⁺ + H₂PO₄^–
(ii) H₂PO₄^– + H₂O →  HPO₄^2– + H₃O⁺
(iii) H₂PO₄^– + OH– →  H₃PO₄+ O^2–
In which of the above, does H₂PO₄^– act as an acid ?
(A) (ii) only
(B) (i) and (ii)
(C) (iii) only
(D) (i) only
Answer : A

Question : How many litres of water must be added to 1 litre an aqueous solution of HCl with a pH of 1 to create an aqueous solution with pH of 2 ? 
(A) 0.1 L
(B) 0.9 L
(C) 2.0 L
(D) 9.0 L
Answer : D

Question : The substance not likely to contain CaCO₃ is : 
(A) calcined gypsum
(B) sea shells
(C) dolomite
(D) a marble statue
Answer : A

Question : Tooth pastes are generally 
a. natural
b. acidic
c. basic
d. neutral
Answer : C
Explanation: Toothpastes are generally basic because their function is to react with the excess acid in our mouth and thus prevent tooth decay. 

Question : In the following schematic diagram for the preparation of hydrogen gas as shown in the figure, what would happen if the following changes are made?

i. In place of zinc granules, same amount of zinc dust in taken in the test tube.

ii. Instead of dilute sulphuric acid, dilute hydrochloric acid is taken.

iii. In place of zinc, copper turnings are taken.

iv. Sodium hydroxide is taken in place of dilute sulphuric acid and the test tube is heated. 

Answer : i. Since the zinc dust has a larger surface area than zinc granules. If the same amount of zinc dust is taken in the test tube then the reaction will be comparatively faster and hydrogen gas will evolve with greater speed.

ii. With dilute hydrochloric acid, almost the same amount of gas is evolved.

iii. With copper turnings, hydrogen gas will not evolve because copper is less reactive and it will not displace hydrogen from the acid. Hence, no reaction will take place.

iv. Zinc also reacts with NaOH. So, if sodium hydroxide is taken, then hydrogen gas will be evolved.