CBSE Class 10 Science Chemical Reactions and Equations VBQs

Question. Which of the reactions is used in black and white photography?
(a) Combination Reaction
(b) Decomposition Reaction
(c) Displacement reaction
(d) Oxidation reaction
Answer : B

Question. 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 : C

Question. Which option shows oxidation?
(a) Zn → Zn²⁺
(b) 2H+ → H₂
(c) Zn²⁺ → Zn
(d) H₂ → 2H
Answer : A

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. A substance X which is a group 2 element is used intensively in the cement industry. This element is present in bones also. On treatment with water, it forms a solution which turns red litmus blue. Element X is
(a) Cu
(b) Ca
(c) Na
(d) Al
Answer : B

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

Question. On immersing an iron nail in CuSO₄ solution for few minutes
(a) no reaction takes place
(b) the colour of solution fades away
(c) the surface of iron nails acquires a black coating
(d) the colour of solution changes to green
Answer : D

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

Question. In the process of burning of magnesium in air, magnesium undergoes -
(a) reduction
(b) sublimation
(c) oxidation
(d) all of these

Answer : C

Question. Neutralization reaction is an example of -
(a) exothermic reaction
(b) endothermic reaction
(c) oxidation reaction
(d) none of these

Answer : A

Question. In the reaction Mg + Cl2 → MgCl2 Chlorine may be regarded as -
(a) an oxidising agent
(b) a reducing agent
(c) a catalyst
(d) providing an inert medium

Answer : A

Question. Which of the following equations is representing combination of two elements ?
(a) CaO + CO2 → CaCO3
(b) 4Na + O2 →2Na2O
(c) SO2 + 1/2 O2 → SO3
(d) 2Na + 2H2O →2NaOH + H2

Answer : B

Question. Which of the following statements is/are true ?
(a) The total mass of the system remains same in a chemical change.
(b) A chemical change is permanent and irreversible.
(c) A physical change is temporary and reversible.
(d) All of these.

Answer : D

Question. H2SO4 + 2NaOH → Na2SO4 + 2H2O
Above equation is a -
(i) neutralization reaction
(ii) double displacement reaction
(iii) decomposition reaction
(iv) addition reaction
(a) (i) to (iv) all
(b) (i) and (ii)
(c) (i) and (iii)
(d) (ii) and (iv)

Answer : B

Question. A substance which oxidises itself and reduces other is known as -
(a) an oxidising agent
(b) a reducing agent
(c) Both of these
(d) None of these

Answer : B

Question. A redox reaction is one in which -
(a) both the substances are reduced.
(b) both the substances are oxidised.
(c) an acid is neutralised by the base.
(d) one substance is oxidised, while the other is reduced.

Answer : D

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. Corrosion of silver occurs due to the formation of
(a) Ag2O
(b) AgCl
(c) Ag2CO3
(d) Ag2S

Answer : D

Question. Which of the following is an example of oxidation reaction ?
(a) Sn +2 – 2e- → Sn+4
(b) Fe+3 + e- → Fe+2
(c) Cl2 + 2e- → 2Cl-
(d) None of these

Answer : A

Question. Which of the following reactions is/are a double displacement reaction(s) ?
(i) AgNO3 + NaBr → NaNO3 + AgBr
(ii) BaCl2 + H2SO4 → BaSO4 + 2HCl
(iii) As2O3 + 3H2S → As2S3 + 3H2O 
(iv) NaOH + HCl → NaCl + H2O
(a) (i) & (ii)
(b) only (iii)
(c) only (iv)
(d) (i) to (iv) all

Answer : D

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. 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.
(b) 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 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. AgNO3 (aq) + NaCl (aq) → AgCl(s) + NaNO3(aq)
Above reaction is a -
(a) precipitation reaction
(b) double displacement reaction
(c) combination reaction
(d) (A) and (B) both

Answer : D

Question. H2S(g) + Cl2 (g) → 2 HCl(g) + S(s)
The reaction is interpreted as : 
(a) H2S is getting oxidised and Cl2 is getting reduced
(b) H2S is getting reduced and Cl2 is getting oxidised
(c) Only H2S is oxidised
(d) Both H2S and Cl2 are reduced

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 endothermic reaction ? 
(a) C(s) + O2(g) → CO2(g)
(b) N2(g) + O2(g) → 2NO(g)
(c) 2H2(g) + O2(g) → 2H2O(l)
(d) 2CH3OH (l) + 3O2(g) → 2CO2(g)+4H2O(l)

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 are correct.

Answer : D

Ammonia is manufactured industrially from nitrogen and hydrogen by the Haber’s process using Fe as catalyst according to the equation:
N₂(g) + 3H₂(g) ⇌ 2NH₃(g)  

Question. If we consider decomposition of ammonia back into nitrogen and hydrogen molcules then the reaction is favoured by   
(a) low temperature and high pressure
(b) low temperature and low pressure
(c) high temperature and high pressure
(d) high temperature and low pressure

Answer : D

Question. Under what pressure higher percentage of NH₃ can be obtained?   
(a) 200 atm
(b) 400 atm
(c) 600 atm
(d) 800 atm

Answer : D

Question. What type of reaction is involved in Haber’s Process?   
(a) Displacement
(b) Endothermic
(c) Exothermic
(d) Decomposition

Answer : C

Question. What does the symbol ‘⇌’ mean?    
(a) Irreversible reaction
(b) Decomposition reaction
(c) Reversible reaction
(d) Redox reaction

Answer : C

Question. Under what condition of temperature higher percentage of NH3 can be obtained.   
(a) 300° C
(b) 400° C
(c) 500° C
(d) 600° C

Answer : A

A student took HCl in a conical flask and was placed on a white tile with cross mark. When seen through the flask the mark was visible. On adding some sodium thiosulphate in the flask the cross mark disappeared when seen through the flask. The student observed some reaction as the products formed were different than the reactants. Both the reactants were transparent. 

Question. Name the resultant insoluble substance formed in the flask    
(a) Copper(II) iodide
(b) Potassium hydroxide
(c) Sulphur
(d) Sodium Thiosulphate

Answer : C

Question. Why did the cross mark disappear?     
(a) The solution formed in the flask does not allow the light to pass through it to see the cross mark
(b) The sulphur is a colloid in this reaction, staying in suspension and eventually blocking the light from reaching the solution
(c) The solution transforms from being colourless to being milky and entirely opaque
(d) All of the above

Answer : D

Question. What type of reaction occurs in the flask?    
(a) Displacement reaction
(b) Double displacement reaction
(c) Photo-chemical decomposition
(d) Thermal decomposition

Answer : B

Question. Name the type of reaction seen in the set up.    
(a) Combustion
(b) Combination
(c) Precipitation
(d) Decomposition

Answer : C

Question. Select the correct reaction for the above chemical reaction    
(a) Na₂S₂O₃ (aq) + 2HCl (aq) → 2NaCl (aq) + H₂O(l) + SO₂ (g) + S(s)
(b) S₂O₃ ^–2 (aq) + 2H+ (aq) → H₂O (l) + SO₂ (g) + S(s)
(c) Na₂S₂O₃ (aq) + 2HCl (aq) → 2NaCl (aq) + SO₂ (g) + S(s)
(d) None of the above

Answer : A

ASSERTION- REASON TYPE QUESTIONS

DIRECTION: Each of these questions contains an assertion followed by reason. Read them carefully and answer the question on the basis of following options. You have to select the one that best describes the two statements.
(a) If both Assertion and Reason are correct and reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are correct, but reason is not the correct explanation of Assertion.
(c) If Assertion is correct but Reason is incorrect.
(d) If Assertion is incorrect but Reason is correct.

Question. Assertion (A): Photosynthesis is considered as an endothermic reaction.
Reason (R): Energy gets released in the process of photosynthesis
Answer : C

Question. Assertion (A): Decomposition of vegetable matter into compost is an example of exothermic reactions.
Reason (R): Exothermic reaction are those reactions in which heat is evolved.
Answer : A

Question. Assertion (A): When HCl is added to zinc granules, a chemical reaction occurs.
Reason (R): Evolution of a gas indicates that the chemical reaction is taking place.
Answer : A

Question. Assertion (A): Calcium carbonate when heated gives calcium oxide and water.
Reason (R): On heating calcium carbonate, decomposition reaction takes place.
Answer : A

Question. Assertion (A): Chemical reaction changes the physical and chemical properties of a substance
Reason (R): Chemical change involves a change in the chemical composition of matter, and a new substance is formed
Answer : A