MCQ Questions for Class 10 Science Chapter 1 Chemical Reactions And Equations

Q.1. 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 Answer: a

Q.2.  The chemical formula of lead sulphate is     
(a)  Pb2SO4
(b)  Pb(SO4)2
(c)  PbSO4
(d)  Pb2(SO4)3

Answer Answer: c

Q.3. 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 Answer: b

Q.4.  Which information is not conveyed by a balanced chemical equation?     
(a)  Physical states of reactants and products     
(b)  Symbols and formulae of all the substances involved in a particular reaction     
(c)  Number of atoms/molecules of the reactants and products formed     
(d)  Whether a particular reaction is actually feasible or not

Answer Answer: d

Q.5. 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 Answer: d

Q.6.  Chemically rust is     
(a)  hydrated ferrous oxide
(b)  only ferric oxide
(c)  hydrated ferric oxide
(d)  none of these

Answer Answer: c

Q.7. 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 disap¬pears. 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 Answer: a

Q.8.  Both CO2 and H2 gases are     
(a)  heavier than air
(b)  colourless
(c)  acidic in nature
(d)  soluble in water

Answer Answer: b

Q.9. Pb + CuCl2 → PbCl2 + Cu
The above reaction is an example of:
(a) combination
(b) double displacement
(c) decomposition
(d) displacement

Answer Answer: d

Q.10.  Which of the following gases can be used for storage of fresh sampel of an oil for a long time?     
(a)  Carbon dioxide or oxygen
(b)  Nitrogen or helium     
(c)  Helium or oxygen
(d)  Nitrogen or oxygen

Answer Answer: b

Q.11. 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 Answer: d
Explanation: 2Fe + 6HCl → 2FeCl3 (Iron (III) chloride) + 3H2

Q.12.  The electrolytic decomposition of water gives H2 and O2 in the ratio of     
(a)  1 : 2 by volume
(b)  2 : 1 by volume
(c)  8 : 1 by mass
(d)  1 : 2 by mass

Answer Answer: b

Q.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

Answer Answer: b

Q.14.  In the decomposition of lead (II) nitrate to give lead (II) oxide, nitrogen dioxide and oxygen gas, the coefficient of nitrogen dioxide (in the balanced equation) is     
(a)  1
(b)  2
(c)  3
(d)  4

Answer Answer: d

Q.15. 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 Answer: c

Q.16.  Fatty foods become rancid due to the process of     
(a)  oxidation
(b)  corrosion
(c)  reduction
(d)  hydrogenation

Answer Answer: a

Q.17. A substance added to food containing fats and oils is called:
(a) Oxidant
(b) Rancid
(c) Coolant
(d) Antioxidant

Answer Answer: d

Q.18.  We store silver chloride in a dark coloured bottle because it is     
(a)  a white solid
(b)  undergoes redoc reaction     
(c)  to avoid action by sunlight
(d)  none of the above

Answer Answer: c

Q.19. Select the oxidising agent for the following reaction:
H2S + I2 → 2HI + S
(a) I2
(b) H2S
(C) HI
(d) S

Answer Answer: a

Q.20.  Silver article turns black when kept in the open for a few days due to formation of     
(a)  H2S
(b)  AgS
(c)  AgSO4
(d)  Ag2S

Answer Answer: d

Q.21. What type of chemical reactions take place when electricity is passed through water?
(a) Displacement
(b) Combination
(c) Decomposition
(d) Double displacement

Answer Answer: c

Q.22.  When crystals of lead nitrate are heated strongly in a dry test tube     
(a)  crystals immediately melt
(b)  a brown residue is left     
(c)  white fumes appear in the tube
(d)  a yellow residue is left

Answer Answer: b

Q.23. 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 Answer: b

Q.24.  Dilute hydrochloric acid is added to granulated zinc taken in a test tube. The following observations are recorded. Point out the correct observation.     
(a)  The surface of metal becomes shining     
(b)  The reaction mixture turns milky     
(c)  Odour of a pungent smelling gas is recorded     
(d)  A colourless and odourless gas is evolved

Answer Answer: d

Q.25. When Ag is exposed to air it gets a black coating of
(a) AgNO3
(b) Ag2S
(c) Ag2O
(d) Ag2CO3

Answer Answer: b

Q.26. 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 Answer: a

Q.27.  When carbon dioxide is passed through lime water,     
(a)  calcium hydroxide is formed
(b)  white precipitate of CaO is formed     
(c)  lime water turns milky
(d)  colour of lime water disappears.

Answer Answer: c

Q.28. 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 Answer: a
Explanation: Reason: In both the cases, heat energy is evolved.

Q.29.  In which of the following, heat energy will be evolved?     
(a)  Electrolysis of water     
(b)  Dissolution of NH4Cl in water     
(c)  Burning of L.P.G.     
(d)  Decomposition of AgBr in the presence of sunlight

Answer Answer: c

Q.30.  When a magnesium ribbon is burnt in air, the ash formed is     
(a)  black
(b)  white
(c)  yellow
(d)  pink

Answer Answer: b

Q.31.  Rancidity can be prevented by     
(a)  adding antioxidants
(b)  storing food away from light     
(c)  keeping food in refrigerator
(d)  all of these

Answer Answer: d

Q.32.  The reaction of H2 gas with oxygen gas to form water is an example of     
(a)  combination reaction
(b)  redox reaction
(c)  exothermic reaction
(d)  all of these reactions

Answer Answer: a

Q.33.  The reaction in which two compound exchange their ions to form two new compounds is called     
(a)  displacement reaction
(b)  combination reaction     
(c)  double displacement reaction
(d)  redox reaction

Answer Answer: c

Q.34.  On immersing an iron nail in CuSO4 solution for few minutes, you will observe     
(a)  no reaction takes place     
(b)  the colour of solution fades away     
(c)  the surface of iron nails acquire a black coating     
(d)  the colour of solution changes to green

Answer Answer: d

Q.35.  An element X on exposure to moist air turns reddish-brown and a new compound Y is formed. The substance X and Y are     
(a)  X = Fe, Y = Fe2O3
(b)  X = Ag, Y = Ag2S
(c)  X = Cu, Y = CuO
(d)  X = Al, Y = Al2O3

Answer Answer: a

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