cbse class 10 science mcq questions pdf download
Chemical Equation And Reaction
Chemical Reaction And Equation
Important MCQs/Very Short Questions With Answers
1. Which of the following is a displacement reaction?
Answer: b
2. Magnesium ribbon is rubbed before burning because it has a coating of
(a) basic magnesium carbonate
(b) basic magnesium oxide
(c) basic magnesium sulphide
(d) basic magnesium chloride
Answer: a
3. Which of the following statements about the given reaction are correct?
3Fe (s) + 4H2O (g) → Fe3O4 (s) + 4 H2 (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), (zi) and (iii)
(b) (in) and (iv)
(c) (i), (ii) and (iv)
(d) (ii) and (iv)
Answer: c
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) (ii) and (iv)
Answer: a
Explanation: Reason: In both the cases, heat energy is evolved.
5. Oxidation is a process which involves
(a) addition of oxygen
(b) addition of hydrogen
(c) removal of oxygen
(d) removal of hydrogen
Answer: a
6. The process of reduction involves
(a) addition of oxygen
(b) addition of hydrogen
(c) removal of oxygen
(d) removal of hydrogen
Answer: b
7. Three beakers labelled as A, B and C each containing 25 ml of water were taken. A small amount of NaOH, anhydrous CuSO4 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 solution 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 occuBftd.
(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) (iv), (ii) and (iii)
Answer: c
8. Give the ratio in which hydrogen and oxygen are present in water by volume.
(a) 1:2
(b) 1:1
(c) 2:1
(d) 1:8
Answer: a
9. 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
Answer: a
10. MnO2 + 4HCl → 2 + 2H2O + Cl2
Identify the substance oxidized in the above . equation.
(a) MnCl2
(b) HCl
(c) H2O
(d) MnO2
Answer: d
Explanation: Reason: In this reaction HCl is oxidised to Cl2, whereas MnO2 is reduced to MnCl2.
11. A substance ‘X’ is used in white-washing and is obtained by heating limestone in the absence of air. Identify ‘X’.
(a) CaOCl2
(b) Ca (OH)2
(c) CaO
(d) CaCO3
Answer:
12. When Ag is exposed to air it gets a black coating of
(a) AgNO3
(b) Ag2S
(c) Ag2O
(d) Ag2CO3
Answer: b
13. Which of the following is an endothermic process?
(a) Dilution of sulphuric acid
(b) Sublimation of dry ice
(c) Condensation of water vapours
(d) Respiration in human beings
Answer: b
14. 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)
(&) Lead acetate
(c) Ammonium nitrate
(d) Potassium sulphate
Answer: b
15. What type of chemical reactions take place when electricity is passed through water?
(a) Displacement
(b) Combination
(c) Decomposition
(d) Double displacement
Answer: c
16. Select the oxidising agent for the following reaction:
H2S + I2 > 2HI + S
(a) I2
(b) H2S
(C) HI
(d) S
Answer: a
17. A substance added to food containing fats and oils is called:
(a) Oxidant
(b) Rancid
(c) Coolant
(d) Antioxidant
Answer: d
18. The condition produced by aerial oxidation of fats and oils in foods marked by unpleasant smell and taste is called:
(a) antioxidation
(b) reduction
(c) rancidity
(d) corrosion
Answer: c
19. 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
Answer: b
20. When S02 gas is passed through saturated solution of H2S, which of the following reaction occurs?
(a) SO2 + 2H2S → 2H20 + 3S
(b) SO2 + 2H2S → H20 + 3S
(c)SO2 + H2S → H2O + S
(d) SO2 + H2O → SO3 + H2
Answer: a
21. Name the products formed when iron filings are heated with dilute hydrochloric acid
(a) Fe (III) chloride and water
(b) Fe (II) chloride and water
(c) Fe (II) chloride and hydrogen gas
(d) Fe (III) chloride and hydrogen gas
Answer: d
Explanation: Reason: 2Fe + 6HCl → 2FeCl3 (Iron (III) chloride) + 3H2
22. Pb + CuCl2 → PbCl2 + Cu
The above reaction is an example of:
(a) combination
(b) double displacement
(c) decomposition
(d) displacement
Answer: d
23. Which of the following gases can be used for storage (a) Carbon dioxide or Oxygen
(b) Nitrogen or Oxygen
(c) Carbon dioxide or Helium
(d) Helium or Nitrogen
Answer: d
24. 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 de-composes in presence of FeSO4. to a colourless compound.
Answer: a
25. 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 (l)
(c) 2H2 (g) + O2 (g) > 2H2O (l)
(d) 2H2 (g) +O2 (g) > 2H2O (g)
Answer: d
26. When green coloured ferrous sulphate crystals are heated, the colour of the crystal changes because
(a) it is decomposed to ferric oxide
(b) it loses water of crystallisation
(c) it forms SO2
(d) it forms SO3
Answer: b
27. 2HNO3 + Ca(OH)2 → Ca(NO3)2 + 2H2O; is an example of
(i) displacement reaction
(ii) double displacement reaction
(iii) neutralisation reaction
(iv) combination reaction.
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (i) and (iv)
Answer: b
28. Burning Magnesium ribbon is brought in the gas jar of carbon dioxide. Which of the following is correct ?
(i) It keeps on burning
(ii) It gets extinguished
(iii) Although CO2 is non-supporter of combustion but burning magnesium breaks CO2 into carbon and oxygen, oxygen helps in burning.
(iv) Carbon dioxide is supporter of combustion.
(a) (i) and (iv)
(b) (i) and (iii)
(c) (i) and (ii)
(d) (iii) and (iv)
Answer: b
29. What is observed when a solution of potassium iodide is added to silver nitrate solution ?
(a) No reaction takes place
(b) White precipitate of silver iodide is formed
(c) yellow precipitate of Agl is formed
(d) Agl is soluble in water.
Answer: c
30. Identify ‘x’, ‘y’ and ‘z’ in the following balanced reaction
(a) 2, 4, 2
(b) 2, 2, 4
(c) 2, 4, 4
(d) 4, 2, 2
Answer: b
31. Which of the following is precipitation as well as double displacement reaction?
Answer: d
32. Which of the following reactions will not take place ?
(a) Zn + CuSO4 → ZnSO3 + Cu
(b) 2KBr + Cl2 → KCl + Br2
(c) Zn + MgSO4 → ZnSO4 + Mg
(d) Mg + FeSO4 → MgSO4 + Fe
Answer: c
33. Which of the following involves combination of two elements ?
(a) N2(g) + 3H2(g) → 2NH3(g)
(b) CaO(s) + CO2(g) → CaCO3(g)
(c) 2SO2(g) + O2(g) → 2SO3f(g)
(d) NH3(g) + HCl(g) → NH4Cl(s)
Answer: a
34. In the reaction Hg2Cl2 + Cl2 → 2HgCl2 The reducing agent is
(a) Hg2Cl2
(b) Cl2
(c) HgCl2
(d) Both Cl2 and HgCl2
Answer: a
35. Oxidation involves
(i) gain of electron
(ii) loss of electron
(iii) addition of oxygen or electronegative element
(iv) removal of hydrogen electropositive element
(a) (i), (ii), (iii)
(b) (ii), (iii), (iv)
(c) (i), (iii), (iv)
(d) (i), (ii), (iv)
Answer: b
36. The formula of Ammonium phosphate is
(a) NH4PO4
(b) (NH4)2PO4
(c) (NH4)3PO4
(d) (NH4)3(PO4)2
Answer: c
37. Which of the following is a thermal decomposition reaction ?
(a) 2H2O → 2H2 + O2
(b) 2AgCl → 2Ag + Cl2
(c) ZnCO3 → ZnO + CO2
(d) H2(g) + Cl2(g) → 2HCl(g)
Answer: c
38. The following reaction is an example of a
4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g)
(i) displacement reaction
(ii) combination reaction
(iii) redox reaction
(iv) neutralisation reaction [NCERT Exemplar Problems]
(a) (i) and (iv)
(b) (ii) and (iii)
(c) (i) and (iii)
(d) (iii) and (iv)
Answer: c
39. Which of the following statements about the given reaction are correct ?
3Fe(s) + 4H2O(g) → Fe3O4(g) + 6H2(g)
(i) Iron metal is getting oxidised
(ii) Water is getting reduced
(iii) Water is acting as reducing agent
(iv) Water is acting as an oxidising agent [NCERT Exemplar Problems]
(a) (i), (ii) and (iii)
(b) (iii) and (iv)
(c) (i), (ii) and (iv)
(d) (ii) and (iv)
Answer: c
40. 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) [NCERT Exemplar Problems]
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (i) and (iv)
(d) (iii) and (iv)
Answer: a
41. Which among the following is (are) double displacement reactions ? [NCERT Exemplar Problems]
(i) Pb + CuCl2 → PbCl2 + Cu
(ii) Na2SO4 + BaCl2 → BaSO4 + 2NaCl
(iii) C + O2 → CO2
(iv) CH4 + 2O2 → CO2 + 2H2O
(a) (i) and (iv)
(b) (ii) only
(c) (i) and (ii)
(d) (iii) and (iv)
Answer: b
42. 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 ? [NCERT Exemplar Problems]
(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)
Answer: d
43. Electrolysis of water is a decomposition reaction. The molar ratio of hydrogen and oxygen gases liberated during electrolysis of water is [NCERT Exemplar Problems]
(a) 1 : 1
(b) 2 : 1
(c) 4 : 1
(d) 1 : 2
Answer: b
44. Which of the following is (are) an endothermic process(es) ? [NCERT Exemplar Problems]
(z) 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)
Answer: d
45. Which of the following gases can be used for storage of fresh sample of an oil for a long time? [NCERT Exemplar Problems]
(a) Carbon dioxide or oxygen
(b) Nitrogen or oxygen
(c) Carbon dioxide or helium
(d) Helium or nitrogen
Answer: d
46. 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 ? [NCERT Exemplar Problems]
(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
Answer: a
47. Which one of the following processes involve chemical reactions ? [NCERT Exemplar Problems]
(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
Answer: d
48. In which of the following chemical equations, the abbreviations represent the correct states of the reactants and products involved at reaction temperature ? [NCERT Exemplar Problems]
(a) H2(l) + O2(l) → 2H2O(g)
(b) H2(g) + O2(l) → 2H2O(l)
(c) H2(g) + O2(g) → 2H2O(l)
(d) H2(g) + O2(g) → m2O(g)
Answer: c
49. The brown gas evolved on heating of copper nitrate is
(a) O2
(b) NO2
(c) N2
(d) NO
Answer: b
50. Zinc reacts with silver nitrate to form which compounds?
(a) Zn(NO3)2 + Ag
(b) ZnNO3 + Ag
(c) AgNO3 + Zn(NO3)2
(d) Ag + Zn(NO3)3
Answer: a
Explanation:
(a) Zn + 2AgNO3 → Zn(NO3)2 + 2Ag
51. MnO2 + 4HCl → MnCl2 + H2O + Cl2 The oxidising agent is
(a) MnO2
(b) HCl
(c) MnCl2
(d) Ag + Zn(NO3)3
Answer: a
Explanation:
(a) MnO2 is oxidising agent because it is removing hydrogen from HCl to form Cl2.
52.
The colour of iodine is
(a) green
(b) purple
(c) brown
(d) pink
Answer: b
Explanation:
(b) Iodine is purple in colour.
Direction (Q53 to Q57): In the following Questions, the Assertion and Reason have been put forward. Read the statements carefully and choose the correct alternative from the following:
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.
53. Assertion: AgBr is used on photographic and x-ray film.
Reason: AgBr is photosensitive and changes to Ag and bromine in presence of sunlight and undergoes decomposition reaction.
Answer: a
Explanation:
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
54. Assertion: Magnesium ribbon keeps on burning in atmosphere of nitrogen. Reason: Magnesium reacts with nitrogen to form magnesium nitrides and this reaction is combination reaction.
Answer: a
Explanation:
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
55. Assertion: Zinc reacts with sulphuric acid to form zinc sulphate and hydrogen gas and it is displacement reaction.
Reason: Zinc reacts with oxygen to form zinc oxide.
Answer: b
Explanation:
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
56. Assertion: MnO2 + 4HCl → MnCl2 + Cl2 + 2H2O is redox reaction.
Reason: MnO2 oxides HCl to Cl2 and gets reduced to MnCl2.
Answer: a
Explanation:
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
57. Assertion: A lead nitrate on thermal decomposition gives lead oxide, brown coloured nitrogen dioxide and oxygen gas. Reason: Lead nitrate reacts with potassium iodide to form yellow ppt of lead iodide and the reaction is double displacement as well as precipitation reaction.
Answer: b
Explanation:
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
58. The colour of FeSO4 crystal before ___________ heating is and after heating is ___________ .
Answer:
Explanation: green, reddish brown
59. SO2 + 2H2S → 2H2O + 3S; SO2 is ___________ acting as agent.
Answer:
Explanation: oxidising
60. The reaction Cu + xHNO3 (cone.) → Cu(NO3)2 + yNO2 + zH2O The values of x, y and z are ___________ , ___________ and ___________ .
Answer: 4, 2 and 2
61. A balanced chemical equation has equal masses of various elements in ___________ and ___________ .
Answer:
Explanation: reactants, products
62.
is an example of ___________ reaction.
Answer: decomposition
63. All combustion reactions are oxidation reactions. [True/False]
Answer: True
64. Displacement reaction can be redox reaction also. [True/False]
Answer: True
65. In H2S + Cl2 → 2HCl + S, Cl2 is oxidising agent and H2S is reducing agent. [True/False]
Answer: True
66. CaO + 2HCl → CaCl2 + H2O is neutralisation reaction. [True/False]
Answer: True
67. Chemical reactions are those processes where new substances with old properties are formed. [True/False]
Answer: False
Direction: Match Column I with Column II.
68.
Answer:
(i) (C)
(ii) (D)
(iii) (A)
(iv) (B)
69. State one basic difference between a physical change and a chemical change. [CBSE 2011]
Answer: In physical change, no new substance is formed whereas in a chemical change a new substance(s) is/are formed.
70. What is meant by a chemical reaction? [CBSE 2011]
Answer: The reaction representing a chemical change is called chemical reaction.
71. On what basis is a chemical equation balanced?
Answer: It is based on law of conservation of mass.
72. Balance the given chemical equation:
Al(s) + CuCl2(ag) → AlCl(aq) + Cu(s)
Answer: 2Al(s) + 3CuCl2(aq) → 2AlCl3(aq) + 3Cu(s)
73. Balance the given chemical equation:
74. Balance the given chemical equation:
3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)
75. AgNO3(aq) + NaCl(aq) → AgCl(g) ↓ + NaNO3(aq)
FeS + H2SO4 → FeSO4 + H2S ↑
Consider the above mentioned two chemical equations with two different kinds of arrows ( ↑ and ↓) along with product. What do these two different arrows indicate? [CBSE 2011]
Explanation:
↑ shows the gas evolved whereas ↓ shows insoluble substance (precipitate) formed.
76. Hydrogen being a highly inflammable gas and oxygen being a supporter of combustion, yet water which is a compound made up of hydrogen and oxygen is used to extinguish fire. Why? [CBSE 2011]
Answer: It is because properties of compound (H2O) are different from properties of its constituting elements i.e. H2 and O2.
77. What happens chemically when quicklime is added to water filled in a bucket?
Answer: Quicklime reacts with water to form slaked lime and produces lot of heat and hissing sound.
78. What change in colour is observed when white silver chloride is left exposed to sunlight? State the type of chemical reaction in this change.
Answer: Silver chloride becomes grey. It is a photochemical decomposition reaction.
79. How will you define a reducing agent?
Answer: Reducing agent is a substance which can lose electrons or which can add hydrogen or remove oxygen.
80. Potato chips manufacturers fill the packet of chips with nitrogen gas. Why? [DoE]
Answer: To provide an inert atmosphere to prevent chips from getting oxidised. N2 does not allow chips to get spoiled by oxidation.
81. Why do gold and platinum not corrode in moist air?
Answer: They are least reactive and do not react with substances present in moist air.
82. Write two characteristics associated with rancid food.
Answer: Unpleasant smell and unpleasant taste.
83. How will you indicate the following effect in a chemical equation? A solution made in water.
Answer: A solution made in water is indicated by writing symbol (aq) with the symbol or formula of the substance concerned, aq stands for aqueous.
84. Give reason for the following:
The burning of natural gas is an exothermic reaction.
Answer: Burning of natural gas is an exothermic reaction because heat is produced in this reaction.
85. Give one example of a redox reaction which is also a combination reaction.
Answer: 2Mg + O2 → 2MgO
86. Balance the given chemical equation:
HNO3 + Ca(OH)2 → Ca(NO3)2 + H2O
Answer: 2HNO3(aq) + Ca(OH)2(aq) > Ca(N03)2(^) + 2H2O(l)
Fill in the Blanks
1. The addition of oxygen to a substance is called …………. whereas removal of oxygen is called …………. .
2. The addition of hydrogen to a substance is called …………. whereas removal of hydrogen is called …………. .
3. Precipitation reactions produce insoluble …………. .
4. Reactions in which energy is given out are known as …………. .
5. Reaction in which an element displaces another element from its compound is called …………. .
6. Two antioxidants which are usually added to fat and oil containing foods to prevent rancidity, are …………., …………. .
7 …………. is the process in which metals are eaten up gradually by the action of air, moisture or a chemical on
their surface.
8. 2 FeSO4 → Fe2O3 + SO2 + ………….
9. Na2SO4 + BaCl2 → …………. + 2NaCl
10. Complete the missing components/variables given as x and y in the following reactions:
(a) Pb (NO3)2 (aq) + 2KI (aq) → Pbl2 (x) + 2KNO3 (y)
(b) Cu (s) + 2AgNO3 (aq) → Cu (NO3)2 (aq) + x (s)
Answers
1. oxidation, reduction
2. reduction, oxidation
3. salts
4. exothermic reactions
5. displacement reaction
6. BHA and BHT
7. Corrosion
8. SO3
9. BaSO4
10. (a) x → (s); y → (aq);
(b) x → 2Ag