Chemical Reactions and Equations (Question Bank)

 📝Chemical Reactions and Equations 

Multiple Choice Questions

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)

Ans: (d)

2) Which one of the following processes involves chemical reactions? 

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

(b) Liquification of air

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

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

Ans: (d)

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

(a) `2H_2 (l) + O_2 (l) rightarrow 2H_2O (g)`

(b) `2H_2 (g) + O_2 (l) rightarrow 2H_2O (l)`

(c) `2H_2 (g) + O_2 (g) rightarrow 2H_2O (l)`

(d) `2H_2 (g) + O_2 (g) rightarrow 2H_2O (g)`

Ans: (c)

4) Which one of the following reactions is an endothermic reaction?

(a) Burning of coal

(b) Decomposition of vegetable matter into composed.

(c) Process of restoration

(d) Decomposition of calcium carbonate to form quick lime and carbon dioxide

Ans: (d)

5) The following reaction is an example of a

`4NH_3(g) + 5O_2(g) \rightarrow  4NO(g) + 6H_2O(g)`

(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)

Ans: (c)

6) Which of the following statements about the given reaction are correct?

`3Fe(s) + 4H_2O(g) \rightarrow Fe_3O_4(s) + 4H_2(g)`

(i) Iron metal is getting oxidised

(ii) Water is getting reduced

(iii) Water is acting as a 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)

Ans: (c)

7) 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)

Ans: (a)

8) Three beakers labelled as A, B and C each containing 25 mL of water were taken. A small amount of `NaOH`, anhydrous `CuSO_4` and `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)

Ans: (c)

9) Which among the following is (are) double displacement reaction(s)?

(i) `Pb + CuCl_2 \rightarrow PbCl_2 + Cu`

(ii) `Na_2SO_4 + BaCl_2 \rightarrow BaSO_4 + 2NaCl`

(iii) `C + O_2 \rightarrow CO_2`

(iv) `CH_4 + 2O_2 \rightarrow  CO_2 + 2H_2O`

(a) (i) and (iv)  (b) (ii) only

(c) (i) and (ii)  (d) (iii) and (iv)

Ans: (b)

10) 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

Ans: (a)

11) Solid calcium oxide reacts vigorously with water to form calcium hydroxide accompanied by the liberation of heat. This process is called slaking of lime. Calcium hydroxide dissolves 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)

Ans: (b)

12) Barium chloride on reacting with ammonium sulphate forms barium sulphate and ammonium chloride. Which of the following correctly represents the type of 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)

Ans: (d)

13) 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

Ans: (b)

14) 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)

Ans: (d)

15) 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

Ans: (b)

16) Which of the following gases can be used for the storage of fresh samples of oil for a long time?

(a) Carbon dioxide or oxygen

(b) Nitrogen or oxygen

(c) Carbon dioxide or helium

(d) Helium or nitrogen

Ans: (d)

17) The following reaction is used for the preparation of oxygen gas in the laboratory

              

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 the release of heat

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

Ans: (a)

18) Which of the following are combination reactions?

(i) `2KClO_3 \overset {Heat}{\rightarrow}2KCl + 3O_2`

(ii) `MgO + H_2O \rightarrow Mg(OH)_2`

(iii) `4Al + 3O_2 \rightarrow  2Al_2 O_3`

(iv) `Zn + Fe_SO_4 \rightarrow ZnSO_4 + Fe`

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

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

Ans:(d)

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Case Studies 

1. Read the following and answer 

Marble’s popularity began in ancient Rome and Greece, where white and off-white marble were used to construct a variety of structures, from hand-held sculptures to massive pillars and buildings.

1.1 The substance not likely to contain `CaCO_3` is

a) Dolomite

b) A marble statue

c) Calcined gypsum

d) Seashells.

Ans: (c)

1.2 A student added 10g of calcium carbonate in a rigid container, secured it tightly, and started to heat it. After some time, an increase in pressure was observed, the pressure reading was then noted at intervals of 5 mins and plotted against time, in a graph as shown below. During which time interval did maximum decomposition take place?

a) 15-20 min

b) 10-15 min

c) 5-10 min

d) 0-5 min

Ans: (d)

1.3 Gas A, obtained above is a reactant for a very important biochemical process that occurs in the presence of sunlight. Identify the name of the process -

a) Respiration

b) Photosynthesis

c) Transpiration

d) sphotolysis

Ans: (b)

1.4 Marble statues are corroded or stained rainwater. Identify the main reason

a) decomposition of calcium carbonate to calcium oxide

b) polluted water is basic in nature hence it reacts with calcium carbonate

c) polluted water is acidic in nature hence it reacts with calcium  carbonate

d) calcium carbonate dissolves in water to give calcium hydroxide.

Ans: (c)

1.5 Calcium oxide can be reduced to calcium, by heating with sodium metal. Which compound would act as an oxidizing agent in the above process?

a) Sodium

b) sodium oxide

c) calcium

d) calcium oxide

Ans: (d)

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Chemical Equations and Reactions

Balance the following equations

a)  `Ca(OH)_2 + HCl \rightarrow CaCl_2 + H_2O`

b)  `NaOH + H_2SO_4 \rightarrow Na_2SO_4 + H_2O`

C)  `NaCl + H_2SO_4  \ rightarrow Na_2SO_4 + HCl`

d)   `Cu + H_2SO_4 \rightarrow CuSO_4 + H_2O + SO_2`

e)  `Al + O_2  \rightarrow Al_2O_3`

f)   `Zn + H_3PO_4  \rightarrow Zn_3(PO_4)_2 + H_2` 

g)  Hydrogen + Chlorine `\rightarrow` Hydrogen chloride 

h)  Barium chloride + Aluminium sulphate `\rightarrow` Barium sulphate + Aluminium chloride. 

i)  Solution of barium chloride and sodium sulphate in water react to give insoluble barrium sulphate and the solution of sodium chloride. ( Balance it.  Type of reaction?)

j)  Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water. (Balance it. Type of reaction?)

Pick the correct option

A. The reaction `H_2 + Cl_2 \rightarrow 2HCl` is a

1. decomposition reaction
2. combination reaction
3. double displacement  reaction
4. displacement  reaction

B.   Which of the following are decomposition reactions?

1. `NaOH + HCl  \rightarrow NaCl + H_2O`
2. `NH_4CNO  \rightarrow  H_2NCONH_2`
3. `2KClO_3 \rightarrow 2KCl + 3O_2`
4. `H_2 + I_2 \rightarrow 2HI`

C.  Which of the following is a displacement reaction?

1. `CaCO_3  \rightarrow CaO + CO_2`
2.  `CaO + 2HCl \rightarrow CaCl_2 + H_2O`
3.  `Fe + CuSO_4  \rightarrow  FeSO_4 + Cu`
4. `NaOH + HCl \rightarrow  NaCl + H_2O` 

1.  Why does the colour of the copper sulphate solution change when an iron nail is dipped in it?

2.   What does one mean by exothermic reaction? Give an example. 

3.  Is copper is more reactive than iron? Give a reaction in support of your answer. 

4. Identify the substances that are oxidised and the substances that are reduced in the following reactions.

`4Na + O_2 \rightarrow 2Na_2O`

`CuO + H_2 \rightarrow Cu + H_2O`

5. When magnesium ribbon burns in the air with dazzling flame and forms white ash, is magnesium oxidized or reduced?

6.  A shiny brown coloured element ‘X’ on heating in the air becomes black in colour. Name the element ‘X’ and the black coloured compound formed.

7. `MnO_2 + 4HCl \rightarrow MnCl_2 + 2H_2O + Cl_2`

       (i)  Name the substance oxidised,  (ii) name the oxidising agent, (iii)  name the substance reduced,           (iv)  name the reducing agent. 

8.  A solution of a substance ‘X’ is used for whitewashing.

• Name the substance ‘X’ and write its formula.
• Write the reaction of the substance ‘X’

9. Which of the statements about the reaction below are incorrect?

 `2PbO + C \rightarrow 2Pb + CO_2`

a) Lead is getting reduced 

b) Carbon dioxide is getting oxidised. 

c) Carbon is getting oxidised.

d) Lead oxide is getting reduced. 

(i) a and b

(ii) a and c

(iii) a, b, and c

(iv) all  

10. Lead nitrate + Potassium iodide, Find the products, which kind of reactions is this? 

 11. A solution of slaked lime is used for whitewashing the wall. After some time, forms a thin layer in the wall. Write the reactions. Which kind of reaction is this?

12. Is 'respiration' is an endothermic or exothermic reaction? Write the reaction. 

13. What form of energy is causing the decomposition reactions?

14.  Take about 2 g barium hydroxide in a test tube. Add 1 g of ammonium chloride and mix with the help of a glass rod. Touch the bottom of the test tube with your palm. What do you feel? Is this an exothermic or endothermic reaction? Also, write the reaction.

15. Why should a magnesium ribbon be cleaned before burning in air?

Assertion - Reasoning-based questions

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true and R is not the correct explanation of A

(c) A is true but R is false 

(d) A is False but R is true

Assertion (A): A white-washed wall develops a coating of calcium carbonate after a few days.

 Reason (R): Calcium oxide on the wall reacts slowly with carbon dioxide in the air.