CBSE Class 10 Chemistry Chemical Reactions And Equations Worksheet Set A

Question. In the balanced equation -
aHgS+bHCl + cHNO₃ → dH₂HgCl₄ + eNO + fS + gH₂O
The values of b, c, e, and g are respectively -
(A) 2, 2, 4, 12
(B) 6, 1, 1, 2
(C) 12,2, 2, 4
(D) both (B) and (C)
Answer. D

Question. In the reaction FeSO₄ + x → Na₂SO₄ + Fe(OH)₂ , x is -
(A) Na₂SO₄
(B) H₂SO₄
(C) NaOH
(D) none of these
Answer. C

Question. In the reaction the possible state of Ca(OH)₂ is -
(A) liquid.
(B) aqueous.
(C) gaseous.
(D) solid.
Answer. B

Question. The rate of reaction remains same, when -
(A) temperature of the reaction changes.
(C) both (A) and (B) are correct
(B) catalyst is added to reaction mixture.
(D) none of these is correct
Answer. D

Question. aK₂Cr₂O₇ + bKCl + cH₂SO₄ → xCrO₂Cl₂ + y KHSO₄ + zH₂O
The above equation balances when
(A) a = 2, b = 4, c = 6 and x = 2, y = 6 , z = 3
(B) a = 4, b = 2, c = 6 and x = 6, y = 2, z = 3
(C) a = 6, b = 4, c = 6 and x = 6, y = 3, z = 2
(D) a = 1, b = 4, c = 6 and x = 2, y = 6, z = 3
Answer. D

Question. In the reaction Mg + Cl₂ → MgCl₂
Chlorine may be regarded as -
(A) an oxidising agent
(C) a catalyst
(B) a reducing agent
(D) providing an inert medium
Answer. A

Question. The antioxidant which is used to prevent rancidity in foods is
(A) butylated hydroxyl anisole.
(B) sodium hydroxide.
(C) sodium carbonate.
(D) methylated hydroxyl anisole
Answer. A

Question. The colour of the chemical that changes when it is left open in sunlight is -
(A) FeSO₄ (s).
(B) Pb(NO₃)₂ (s)
(C) AgCl (s).
(D) BaCl₂ (aq)
Answer. C

Question. Sun produces heat and light by -
(A) combustion.
(B) inflammation.
(C) nuclear reactions.
(D) photochemical reactions.
Answer. C

Question. Heating of calcium carbonate to give calcium oxide and carbon dioxide is -
(A) An oxidation process
(B) A reduction process
(C) Disproportionation
(D) Decomposition
Answer. D

Question. Which of the following statement(s) is/are correct ?
(A) Many compounds can be used as oxidizing as well as reducing agent .
(B) We need equal moles and equal volumes of strong monobasic acid and strong monoacidic base to completely neutralize themselves.
(C) The quantity of a catalyst does not change at the end of a chemical reaction .
(D) All of these are correct
Answer. D

Question. The elements undergoing reduction and oxidation during the reaction,
(NH₄)₂Cr₂O₇ → N₂ + Cr₂O₃ + 4H₂O are respectively
(A) N and Cr
(B) Cr and N
(C) N and O
(D) Cr and O
Answer. B

Question. The decomposition of KCIO₃ to KCI and O₂ on heating is an example of:
(A) Intermolecular redox change
(B) Intramolecular redox change
(C) Disproportionation or auto redox change
(D) None of the above
Answer. B

Question. Which of the following can act as oxidant ?
(A) H₂O₂
(B) H₂S
(C) NH₃
(D) None of these
Answer. A

Question. Conversion of PbSO₄ to PbS is -
(A) reduction of S
(B) oxidation of S
(C) dissociation
(D) none of these
Answer. A

Question. Which of the following is redox reaction ?
(A) NaOH + HCl → NaCl + H₂O
(B) AgNO₃ + KI → AgI + KNO₃
(C) BaO₂ + H₂SO₄ → BaSO₄ + H₂O₂
(D) SnCI₂ + HgCI₂ → SnCI₄ + Hg
Answer. D

Question. In a conjugate pair of reductant and oxidant, the reductant has :
(A) Lower ox. no.
(B) Higher ox. no.
(C) Same ox. no.
(D) Either of these
Answer. A

Question. Oxidation is process which involves:
(A) De-electronation
(B) Electronation
(C) Addition of hydrogen
(D) Addition of metal
Answer. A

Question. Oxidants are substances which :
(A) Show a decrease in their oxidation number during a change
(B) Gain electrons during a change
(C) Oxidise others and reduce themselves
(D) All of the above
Answer. D

Question. If an iron rod is dipped in CuSO₄ solution :
(A) Blue colour if the solution turns red
(B) Brown layer is deposited on iron rod
(C) No change occurs in the colour of the solution
(D) None of the above
Answer. B

Question. Which of the following is a redox reaction ?
(A) CaCO₃ → CaO + CO₂
(B) H₂ + Cl₂ → 2HCl
(C) CaO + 2HCl → CaCl₂ + H₂O
(D) NaOH + HCl → NaCl + H₂O
Answer. B

Question. Which of the following statement about the following reaction is correct
ZnO + CO → Zn + CO₂
(A) ZnO is being oxidised
(B) CO is being reduced
(C) CO2 is being oxidised
(D) ZnO is being reduced
Answer. D

Question. Calorific value of a fuel may be defined as -
(A) The amount of heat produced when 1000 kg of a fuel is completely burnt.
(B) The amount of heat produced when 1 g of fuel is incompletely burnt.
(C) The amount of heat produced when 10 g of a fuel is completely burnt.
(D) The amount of heat produced in kilojoules when unit mass of a fuel is completely burnt.
Answer. D

Question. Which of the following fuels has the highest calorific value ?
(A) Petrol
(B) Hydrogen
(C) LPG
(D) Natural gas
Answer. B

Question. In which zone of a candle flame does complete combustion take place ?
(A) Inner
(B) Outer
(C) Middle
(D) All three zones
Answer. B

Question. The zone of no combustion is -
(A) the middle zone
(B) outermost zone
(C) the base of the flame
(D) innermost zone.
Answer. D

Question. The colour of the flame in luminous zone is -
(A) blue.
(B) red.
(C) yellow.
(D) black.
Answer. C

Question. The non-combustible substance among the following is -
(A) coal.
(B) glass.
(C) wood.
(D) paper.
Answer. B

Question. Combustion is a -
(A) physical process
(B) chemical process
(C) biological process
(D) mechanical process
Answer. B

Question. A circular blackish ring on the glass plate kept over the candle flame indicates-
(A) complete combustion.
(B) dark zone of the flame.
(C) non-luminous zone.
(D) luminous zone
Answer. D

Question. Combustion is a process involving -
(A) oxidation
(B) reduction
(C) liberation of heat
(D) all(A),(B) & (C)
Answer. D

CASE STUDY BASED QUESTIONS:

Question. Read the following and answer the questions :

A student was asked to investigate what happens when a piece of shiny magnesium ribbon is added to copper sulphate solution. The apparatus was set up as shown below. The mass was recorded at the start and again after one hour.

Question. Complete the equation:
Mg + CuSO₄ →--------- + ---------
(a) MgSO₄ + Cu
(c) MgS + Cu₂O
(b) MgO + Cu
(d) Mg SO₃ + Cu₂O
Answer. A

Question. Choose from below the name given to this type of reaction:
(a) Combustion
(b) Displacement
(c) Corrosion
(d) Electrolysis
Answer. B

Question. Balance the following symbol equation that represents the displacement reaction that takes place between zinc and silver nitrate solution.
Zn + AgNO₃ → Zn(NO₃)₂ + Ag
(a) Zn + 2AgNO₃ → Zn(NO₃)₂ + 2Ag
(b) Zn + 3AgNO₃ → Zn(NO₃)₂ + 3Ag
(c) Zn + 2AgNO₃ → Zn(NO₃)₂ + Ag
(d) 2 Zn + AgNO₃ → Zn(NO₃)₂ + Ag
Answer. A

Question. The experiment was repeated using sodium sulphate solution instead of copper sulphate solution.
No reaction took place. Put the metals copper, magnesium and sodium in order of reactivity.
(a) I. Sodium II Copper III Magnesium
(b) I Magnesium II Copper III Sodium
(c) I. Copper II. Magnesium III. Sodium
(d) I. Sodium II. Magnesium III. Copper
Answer. D

Question. What will be the mass of the beaker and content after 1 hour?
(a.) More than 80.6 g
(b) Equal to 80.6 g
(c) Less than 80.6 g
(d) None of the above
Answer. B

Read the following and answer the questions :

Called the reducing agent; when the reaction occurs, it reduces the other species. In other words, what is oxidized is the reducing agent and what is reduced is the oxidizing agent.
A good example of a redox reaction is the thermite reaction, in which iron atoms in ferric oxide
lose (or give up) O atoms to Al atoms, producing Al₂O₃.
Fe₂O₃ (s) +2Al (s)→Al₂O₃ (s)+2Fe (l)
Redox reactions can occur relatively slowly, as in the formation of rust, or much morerapidly, as in the case of burning fuel. There are simple redox processes, such as theoxidation

Question. Which of the following is correct code for X and Y in the following reaction ?

(i) x=oxidation reaction, y=reduction reaction
(ii) x=gain of two electrons, y=loss of two electrons,
(iii) x=reduction reaction, y=oxidation reaction
(iv) x=loss of two electrons, y=gain of two electrons
(a) (i) and (ii)
(b) (i) and (iv)
(c) (ii) and (iii)
(d) (iii) and (iv)
Answer. B

Question. A substance which oxidizes itself and reduces other is known as:
(a) Oxidizing agent
(b) Reducing agent
(c) Both of these
(d) None of these
Answer. B

Question. ‘Thermite is a pyrotechnic composition of metal powder, which serves as fuel, and metal oxide.
When ignited by heat, thermite undergoes a reaction between iron and Aluminum Oxide and is used in the wielding of railway tracks. The type of reaction is called:
a) Reduction
c) Redox
b) Oxidation
d) Decomposition
Answer. C

Question. “Redox reactions can occur relatively slowly, as in the formation of rust, or much more rapidly, as in the case of burning fuel” Rusting and combustion are quite different. Which of the following lines is not the correct explanation for this?
(a) Rusting occurs at the surface of iron to form a layer of rust.
(b) Rusting gives out lots of heat and light.
(c) Rusting is an example of slow oxidation.
(d) It can be hampered by applying paint.
Answer. B

Question. Reduction can be defined as:
(a) Gain of electrons
(b) Gain of Oxygen
(c) Loss of Hydrogen
(d) Loss of electrons
Answer. A

Read the following and answer the questions :

Oxidation is the process of gaining of oxygen, or losing of hydrogen. Reduction is the process of losing of oxygen or gaining of hydrogen. The substance which undergoes oxidation is the reducing agent while the substance which undergoes reduction is known as the oxidising agent. Oxidation and reduction always take place together and these types of reactions are known as redox reactions. Some of the examples of redox reactions are given below:

Question. Give two examples of oxidation reaction from your everyday life.
Answer. corrosion & rancidity

Question. Write the oxidising agent in the reaction III and VI.
Answer. CuSO₄ in (III) & CuO in(VI)

Question. Which of the following is an oxidising agent?
(a) LiAlH₄
(b) Alkaline KMnO₄
(c) Acidified K2Cr₂O₇
(d) Both (b) and (c)
Answer. D

Question. Out of oxidation and reduction, which reaction takes place at anode?
Answer. oxidation

Question. Which substance undergoes reduction?
Answer. oxidizing agent

Read the following and answer the questions :

A chemical reaction is a representation of chemical change in terms of symbols and formulae of reactants and products. There are various types of chemical reactions like combination,
decomposition, displacement, double displacement, oxidation and reduction reactions. Reactions in which heat is released along with the formation of products are called exothermic chemical reactions. All combustion reactions are exothermic reactions.

Question. The chemical reaction in which a single substance breaks down into two or more simpler substances upon heating is known as
(a) thermal decomposition reaction
(b) photo decomposition reaction
(c) electric decomposition reaction
(d) both (a) and (c)
Answer. A

Question. The massive force that pushes the rocket forward through space is generated due to the
(a) combination reaction
(b) decomposition reaction
(c) displacement reaction
(d) double displacement reaction
Answer. B

Question. A white salt on heating decomposes to give brown fumes and yellow residue is left behind. The yellow residue left is of
(a) lead nitrate
(b) nitrogen oxide
(c) lead oxide
(d) oxygen gas
Answer. C

Question. Which of the following reactions represents a combination reaction?
(a) CaO (s) + H₂O (l) → Ca(OH)₂ (aq)
(b) CaCO₃ (s) → CaO (s) + CO₂(g)
(c) Zn(s) + CuSO₄ (aq) → ZnSO₄ (aq) + Cu(s)
(d) 2FeSO₄(s) → Fe₂O₃ (s) +SO₂(g) + SO₃(g)
Answer. A

Question. Complete the following statements by choosing correct type of reaction for X and Y.
Statement 1: The heating of lead nitrate is an example of ‘X’ reaction.
Statement 2: The burning of magnesium is an example of ‘Y’ reaction.
(a) X- Combination, Y- Decomposition
(b) X- Decomposition, Y-Combination
(c) X- Combination, Y-Displacement
(d) X- Displacement, Y-Decomposition
Answer. B

Read the following and answer the questions :

Chemical equation is a method of representing a chemical reaction with the help of symbols and formulae of the substances involved in it. In a chemical equation, the substances which combine or react are called reactants and new substances produced are called products. A chemical equation is a short hand method of representing a chemical reaction. A balanced chemical equation has equal number of atoms of different elements in the reactants and products side. An unbalanced chemical equation has unequal number of atoms of one or more elements in reactants and products. Formulae of elements and compounds are not changed to balance an equation.

Question.Consider the following reaction:
pMg₃N₂ + qH₂O ⇾ rMg(OH)₂ + sNH₃
When the equation is balanced, the coefficients p, q, r, s respectively is
(a) 1,3,3,2
(c) 1,6,3,2
(b) 1,2,3,2
(d) 2,3,6, 2
Answer. B

Question. Which of the following 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. D

Question. The balancing of chemical equations is in accordance with
(a) Law of combining volumes
(b) Law of constant proportions
(c) Law of conservation of mass
(d) Both (b) and (c)
Answer. C

Question. Which of the following chemical equations is an unbalanced one?
(a) 2NaHCO₃ ⟶ Na₂CO₃+H₂O+CO₂
(b) 2C₄H₁₀+12O₂ ⟶ 8CO₂+10H₂O
(c) 2Al+6H₂O ⟶ 2Al(OH)₃+3H₂
(d) 4NH₃+5O₂ ⟶ 4NO+6H₂O
Answer. B

Question. Which of the following statements is/are correct?
(a) A chemical equation tells us about the substances involved in a reaction.
(b) A chemical equation informs us about the symbols and formulae of the substances involved in a reaction.
(c) A chemical equation tells us about the atoms or molecules of the reactants and products involved in a reaction.
(d) All the above.
Answer. D

Question. In which of the given, 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 : C

Question. One of the following is an exothermic reaction. This is 
(a) Electrolysis of water
(b) Conversion of limestone into quicklime
(c) Process of respiration
(d) Process of photosynthesis

Answer : C

Question. Which of the following is not an accurate method to prevent rancidity? 
(a) By adding antioxidants
(b) By applying layer of oil or grease
(c) By Vacuum packing
(d) By replacing air with nitrogen

Answer : B

Question. Which Of The Following Is (Are) An Endothermic Process (Es)? 
(a) Dilution of sulphuric acid, and Condensation of water vapours.
(b) Sublimation of dry ice.
(c) Condensation of water vapours.
(d) Sublimation of dry ice, and Evaporation of water

Answer : D

Question. One of the following processes does not involve a chemical reaction, that is: 
(a) Melting of candle wax when heated
(b) Burning of candle wax when heated
(c) Digestion of food in your stomach
(d) Ripening of banana

Answer : A

Question. Which of the given 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

Answer : B

Question. PbS reacts with ozone (O3) and forms pbso4 . As per the balanced equation, molecules of ozone required for every one molecule of PbS is/are 
(a) 4
(b) 3
(c) 2
(d) 1

Answer : A

Question. 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 : A

Question. When ferrous sulphate is heated it decomposes into ferric oxide and the gas liberate in this reaction is : 
(a) SO₂
(b) SO₃
(c) Both
(d) O2

Answer : C

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

Answer : B

Question. Chemically, rust is 
(a) Hydrated ferrous
(b) Only ferric oxide
(c) Hydrated ferric oxide
(d) None of these

Answer : D

Question. The reaction which decomposes after the supply of heat is called 
(a) Thermal decomposition
(b) Combination reaction
(c) Redox reaction
(d) Displacement reaction

Answer : A

Question. When a magnesium ribbon is burrnt in air, the ash formed is 
(a) black
(6) white
(c) yellow
(d) pink

Answer : B

Question. We store silver chloride in a dark coloured bottle because it is 
(a) A white solid
(b) Undergoes redox reaction
(c) To avoid action by sunlight
(d) None of the above

Answer : C

Question. Decomposition reaction are generally : 
(a) precipitative
(b) Exothermic
(c) Endothermic
(d) Redox

Answer : C

Question. What happens when carbon dioxide is passed in lime water? 
(a) Lime water turns milky because of formation of calcium carbonate
(b) Lime water turns milky because of formation of water
(c) Lime water turns red because of formation permanganate
(d) Lime water turns red because of formation of copper sulphate

Answer : A

Question. While balancing a chemical reaction, the only numbers that are added or changed are 
(a) Subscripts
(b) Superscripts
(c) Coefficients
(d) Molar masses

Answer : C

Question. The following reaction is used for the preparation of oxygen gas in the laboratory: Which of the following statement about the reaction is correct? 
(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

Question. Which of the following does not corrode when exposed to the atmosphere- 
(a) Iron
(b) Copper
(c) Gold
(d) Silver

Answer : C

Question. When P reacts with caustic soda, the products are PH3 and NaH₂PO₂. This reaction is an example of 
(a) Oxidation
(b) Reduction
(c) Oxidation and reduction (redox)
(d) Neutralization

Answer : C

Question. In a context of redox reactions, the removal of hydrogen from a substance is known as 
(a) Oxidation
(b) Dehydration
(c) Reduction
(d) Dehydrogenation

Answer : A

Question. 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 : D

Question. Consider The Given Statements And Choose The Incorrect One: 
(a) The bubbles of hydrogen gas are produced, when zinc granules reacts with dilute sulphuric acid.
(b) Hydrogen gas is evolved when magnesium reacts with a dilute acid.
(c) Hydrogen gas is evolved when dilute hydrochloric acid is poured over sodium carbonate.
(d) None of the above.

Answer : C

Question. From the following which one is the example of chemical reaction? 
(a) Grapes get fermented
(b) Breakdown of food
(c) Formation of curd
(d) All of the above

Answer : D

Question. On the basis of evolution or absorption of heat, chemical reactions can be divided in how many types? 
(a) Two
(b) Three
(c) Four
(d) One

Answer : A

Question. What happens when copper rod is dipped in iron sulphate solution :- 
(a) Copper displaces iron
(b) Blue color of copper sulphate solution is obtained
(c) No reaction takes place
(d) Reaction is exothermic

Answer : C

Question. Zn + H₂SO₄(dil) ->ZnSO₄ + H₂ Above reaction is 
(a) Decomposition reaction
(b) Single displacement reaction
(c) Combination reaction
(d) Synthesis reaction

Answer : B

Question. One of the following processes does not involve a chemical reaction. That is: 
(a) Melting of candle wax when heated
(b) Burning of candle wax when heated
(c) Digestion of food in our stomach
(d) Ripening of banana

Answer : A

Question. What is the other name for quick lime? 
(a) Calcium hydroxide
(b) Calcium oxide
(c) Carbon dioxide
(d) Sodium oxide

Answer : B

Question. When Silver is exposed to air it gets a black coating of : 
(a) Silver Nitrate
(b) Silver Oxide
(c) Sliver Sulphide
(d) Silver Carbonate

Answer : C

Question. 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), (zi) and (iii)
(b) (in) and (iv)
(c) (i), (ii) and (iv)
(d) (ii) and (iv)

Answer : C

Question. 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

Question. In the reaction Hg2Cl2 + Cl₂ → 2HgCl₂ The reducing agent is
(a) Hg2Cl₂
(b) Cl₂
(c) HgCl₂
(d) Both Cl₂ and HgCl₂

Answer : A

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

Answer : D

Question. 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

Question. 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

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

Answer : D

Question. MnO₂ + 4HCl → 2 + 2H₂O + Cl₂
Identify the substance oxidized in the above . equation.
(a) MnCl₂
(b) HCl
(c) H₂O
(d) MnO₂

Answer : D

Question. 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

Question. 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

Question. 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

Question. 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

Answer : D

Question. 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

Question. Which of the following is a displacement reaction?
(a) MgCO₃ - → MgO + CO₂
(b) 2Na + 2H₂0 - → 2NaOH + H₂
(c) 2H₂ + O₂ → 2H₂O Heat
(d) 2Pb (NO₃)₂ 2PbO + 4NO₂ + O₂ 

Answer : B

Question. 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

Question. 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

Question. 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

Question. Which of the following is precipitation as well as double displacement reaction?
(a) NaOH(aq)+HNO₃(aq)--------NaNO₃(aq) +H₂O
(b) Cu(s)+2AgNO₃(aq)-------Cu(NO₃)₂(aq)+2Ag(s)
(c) 2Hg(s) + O2(g)---- 2HgO(s) Heat
(d) FeCl3(aq)+ 3NH4OH(aq) ------ Fe(OH)3(s) + 3NH4Cl(aq)

Answer : D

Question. A dilute ferrous sulphate solution was gradu¬ally 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 : A

Question. 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

Question. Oxidation involves
(i) gain of electron
(ii) loss of electron
(iii) addition of oxygen or electronegative element
(iv) removal ofhydrogenorelectropositive element
(a) (i), (ii), (iii)
(b) (ii), (iii), (iv)
(c) (i), (iii), (iv)
(d) (i), (ii), (iv)

Answer : B

Question. 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

Question. 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 
(a) (i), (ii) and (iii)
(b) (iii) and (iv)
(c) (i), (ii) and (iv)
(d) (ii) and (iv)

Answer : C

Question. 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

Question. 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 
(a) (i) and (iv)
(b) (ii) and (iii)
(c) (i) and (iii)
(d) (iii) and (iv)

Answer : C

Question. Electrolysis of water is a decomposition reaction. The molar 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

Question. 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 release of heat
(d) It is a photochemical decomposition reaction and exothermic in nature

Answer : A

Question. 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

Question. Oxidation is a process which involves
(a) addition of oxygen
(b) addition of hydrogen
(c) removal of oxygen
(d) removal of hydrogen

Answer : A

Question. 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)

Answer : A

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

Question. 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

(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.

Question. 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

Question. Assertion: MnO₂ + 4HCl → MnCl₂ + Cl₂ + 2H2O is redox reaction.
Reason: MnO₂ oxides HCl to Cl₂ and gets reduced to MnCl2.

Answer : A

Question. 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

Question. 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

Question. 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

Important Questions for NCERT Class 10 Science Chemical Reactions And Equations

Question : Why should a magnesium ribbon be cleaned before it is burnt in air?
Answer :  Magnesium is an very reactive metal. When stored, it reacts with oxygen to form a layer of magnesium oxide on its surface. This layer of magnesium oxide is quite stable and prevents further reaction of magnesium with oxygen. The magnesium ribbon is cleaned by sand paper for removing this layer so that the underlying metal can be exposed to air.

Question : Write the balanced equation for the following chemical reactions.
(i) Hydrogen + Chlorine → Hydrogen chloride
(ii) Barium chloride + Aluminium sulphate → Barium sulphate + Aluminium chloride
(iii) Sodium + Water → Sodium hydroxide + Hydrogen

Question : Write a balanced chemical equation with state symbols for the following reactions.
(i) Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride.
(ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water)to produce sodium chloride solution and water.
Answer :

Question : A solution of a substance ‘X’ is used for white washing.
(i) Name the substance ‘X’ and write its formula.
(ii) Write the reaction of the substance ‘X’ named in (i) above with water.
Answer : 
(i) The substance ‘X’ is calcium oxide. Its chemical formula is CaO.
(ii) Calcium oxide reacts vigorously with water to form calcium hydroxide (slaked lime).
CaO (s) + H₂O (l) → Ca(OH)₂ (aq)
Calcium Oxide (Quick Lime) + Water → Calcium Hydroxide (Slaked Lime)

Question : Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other? Name this gas.
Answer : 
Water contains two parts of hydrogen and one part oxygen. Therefore, during the electrolysis of water the amount of hydrogen gas collected in one of the test tubes is double than that of the oxygen produced and collected in the other test tube.

Question : Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
Answer : 
When an iron nail dipped in the copper sulphate solution than iron displaces copper