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Chemical Reactions and Equations : NCERT Exemplar


Multiple Choice Questions :

Q.1 Which of the following is not a physical change?

(a) Boiling of water to give water vapour

(b) Melting of ice to give water

(c) Dissolution of salt in water

(d) Combustion of Liquefied Petroleum Gas (LPG)

Sol. (d) 

Q.2 The following reaction is an example of

     4NH3 (g) + 5O2 (g) → 4NO + 6H2O

(i) Displacement reaction

(ii) Combination reaction.

(iii) Redox reaction.

(iv) Neutralisation reaction  

(a) (i) and (iv) (b) (ii) and (iii)

(c) (i) and (iii) (d) (iii) and (iv)

Sol. (d)   

Q.3 Which of the following statements about the given reaction are correct?

            3Fe (s) + 4H2O (g) → Fe3O4 (s) + 4H2 (g)

(i) Iron metal is getting oxidised

(ii) Water is getting reduced

(iii) Water is acting as reducing agent

(iv) Water is acting as oxidising agent

(a) (i), (ii) and (iii)

(b) (iii) and (iv)

(c) (i), (ii) and (iv)

(d) (ii) and (iv)

Sol. (c)  

Q.4 Which of the following are exothermic processes?

(i) Reaction of water with quick lime

(ii) Dilution of an acid

(iii) Evaporation of water

(iv) Sublimation of camphor (crystals)

(a) (i) and (ii)

(b) (ii) and (iii)

(c) (i) and (iv)

(d) (iii) and (iv)

Sol. (a)  

Q.5 Three beakers labelled as A, B and C each containing 25 mL of water was taken. A small amount of NaOH, anhydrous CuSO4and NaCl were added to the beakers A, B and C respectively. It was observed that there was an increase in the temperature of the solutions contained in beakers A and B, whereas in case of beaker C, the temperature of the solution falls. Which one of the following statement(s) is (are) correct?

(i) In beakers A and B, exothermic process has occurred.

(ii) In beakers A and B, endothermic process has occurred.

(iii) In beaker C exothermic process has occurred.

(iv) In beaker C endothermic process has occurred.

(a) (i) only

(b) (ii) only

(c) (i) and (iv)

(d) (ii) and (iii)

Sol. (c)  

Q.6 A dilute ferrous sulphate solution was gradually added to the beaker containing acidified permanganate solution. The light purple colour of the solution fades and finally disappears. Which of the following is the correct explanation for the observation?

(a) KMnO4 is an oxidising agent, it oxidises FeSO4

(b) FeSO4 acts as an oxidising agent and oxidises KMnO4

(c) The colour disappears due to dilution; no reaction is involved

(d) KMnO4 is an unstable compound and decomposes in presence of FeSO4 to a colourless compound.

Sol. (d)

Q. 7 Which among the following is (are) double displacement reaction(s)?

Pb + CuCl2→ PbCl2 + Cu

Na2SO4+ NaCl2 →  BaSO4 + 2NaCl

C + O2→ CO2

CH4+ 2O2  → CO2 + 2H2O

(i) and (iv)

(ii) only

(i) and (iii)

(iii) and (iv)   

Sol. (b) 

Q.8 Which among the following statement(s) is (are) true? Exposure of silver chloride to sunlight for a long duration turns grey due to

(i) The formation of silver by decomposition of silver chloride

(ii) Sublimation of silver chloride

(iii) Decomposition of chlorine gas from silver chloride

(iv) Oxidation of silver chloride

(a) (i) only (b) (i) and (iii)

(c) (ii) and (iii) (d) (iv) only

Sol.  (b)  

Q.9 Solid calcium oxide reacts vigorously with water to form calcium hydroxide accompanied by liberation of heat. This process is called slaking of lime. Calcium hydroxide dissolves readily in water to form its solution called lime water. Which among the following is (are) true about slaking of lime and the solution formed?

(i) It is an endothermic reaction

(ii) It is an exothermic reaction

(iii) The pH of the resulting solution will be more than seven

(iv) The pH of the resulting solution will be less than seven

(a) (i) and (ii) (b) (ii) and (iii)

(c) (i) and (iv) (d) (iii) and (iv)

Sol. (b) 

Q.10 Barium chloride on reacting with ammonium sulphate forms barium sulphate and ammonium chloride. Which of the following correctly represents the type of the reaction involved?

(i) Displacement reaction

(ii) Precipitation reaction

(iii) Combination reaction

(iv) Double displacement reaction

(a) (i) only (b) (ii) only

(c) (iv) only (d) (ii) and (iv)

Sol. (d)   

Q.11 Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is

(a) 1:1

(b) 2:1

(c) 4:1

(d) 1:2

Sol. (b)   

Q.12 Which of the following is (are) an endothermic process (es)?

(i) Dilution of sulphuric acid

(ii) Sublimation of dry ice

(iii) Condensation of water vapours

(iv) Evaporation of water

(a) (i) and (iii) (b) (ii) only

(c) (iii) only (d) (ii) and (iv)

Sol. (d)   

Q.13 In the double displacement reaction between aqueous potassium iodide and aqueous lead nitrate, a yellow precipitate of lead iodide is formed. While performing the activity if lead nitrate is not available, which of the following can be used in place of lead nitrate?

(a) Lead sulphate (insoluble)

(b) Lead acetate

(c) Ammonium nitrate

(d) Potassium sulphate

Sol. (b)   

Q.14 Which of the following gases can be used for storage of fresh sample of an oil for a long time?

(a) Carbon dioxide or oxygen

(b) Nitrogen or oxygen

(c) Carbon dioxide or helium

(d) Helium or nitrogen

Sol. (d)   

Q.15 The following reaction is used for the preparation of oxygen gas in the laboratory

2KClO3 (s) + heat + catalyst →  2KCl + 3O2

Which of the following statement(s) is (are) correct about the reaction?

(a) It is a decomposition reaction and endothermic in nature

(b) It is a combination reaction

(c) It is a decomposition reaction and accompanied by release of heat

(d) It is a photochemical decomposition reaction and exothermic in nature

Sol. (a) 

Q.16 Which one of the following processes involves chemical reactions?

(a) Storing of oxygen gas under pressure in a gas cylinder

(b) Liquefaction of air

(c) Keeping petrol in a china dish in the open

(d) Heating copper wire in presence of air at high temperature

Sol. (d) 

Q.17 In which of the following chemical equations, the abbreviations represent the correct states of the reactants and products involved at reaction temperature?

(a) 2H2 (l) + O2 (l) → 2H2O (g)

(b) 2H2 (g) + O2 (l) → 2H2O (g)

(c) 2H2 (g) + O2 (g) → 2H2O (l)

(d) 2H2 (g) + O2 (g) → 2H2O (g)  

Sol. (c) 

Q.18 Which of the following are combination reactions?

(i) 2KClO3 → 2KCl + 3O2

(ii) MgO + H2O →  Mg(OH)2

(iii) 4Al + 3O2 → 2Al2O3

(iv) Zn + FeSO4 → ZnSO4 + Fe  

(a) (i) and (iii) (b) (iii) and (iv)

(c) (ii) and (iv) (d) (ii) and (iii)

Sol. (d) 


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