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Chemical Reactions and Equations — Class 10 CBSE Science MCQs with Solutions
Free Class 10 CBSE Science Chemical Reactions and Equations MCQs with step-by-step solutions. Practise online on Prepizo — no login needed.
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Sample questions with solutions
Q1 — easy
Burning of magnesium ribbon in air produces a white dazzling flame and forms a white powder of:
A. Magnesium carbonate
B. Magnesium oxide ✓ Correct
C. Magnesium nitride
D. Magnesium sulphate
Solution: Magnesium reacts with atmospheric oxygen to form magnesium oxide (MgO).
Q2 — easy
Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated is:
A. 1 : 1
B. 2 : 1 ✓ Correct
C. 1 : 2
D. 4 : 1
Solution: Water decomposes as 2H₂O → 2H₂ + O₂, yielding H₂ and O₂ in a 2:1 volume/mole ratio.
Q3 — easy
When lead nitrate powder is heated in a boiling tube, brown fumes evolved belong to:
A. Oxygen
B. Nitrogen dioxide (NO₂) ✓ Correct
C. Lead oxide
D. Nitrous oxide
Solution: Thermal decomposition of lead nitrate releases reddish-brown nitrogen dioxide (NO₂) gas.
Q4 — easy
Reaction between quicklime (CaO) and water to form slaked lime Ca(OH)₂ is an example of:
A. Endothermic reaction
B. Exothermic combination reaction ✓ Correct
C. Displacement reaction
D. Decomposition reaction
Solution: CaO + H₂O → Ca(OH)₂ releases a large amount of heat energy.
Q5 — easy
When an iron nail is dipped in blue copper sulphate solution, the solution turns green due to formation of:
A. Iron oxide
B. Ferrous sulphate (FeSO₄) ✓ Correct
C. Copper oxide
D. Zinc sulphate
Solution: Iron displaces copper: Fe + CuSO₄ → FeSO₄ (light green) + Cu.
Q6 — easy
Reactions in which there is an exchange of ions between reactants are called:
A. Displacement reactions
B. Double displacement reactions ✓ Correct
C. Decomposition reactions
D. Redox reactions
Solution: In double displacement reactions, ionic partners are mutually exchanged.
Q7 — easy
Oxidation is a chemical process that involves:
A. Gain of oxygen or loss of hydrogen ✓ Correct
B. Loss of oxygen or gain of hydrogen
C. Gain of hydrogen only
D. Loss of electrons and gain of hydrogen
Solution: Oxidation involves addition of oxygen or removal of hydrogen.
Q8 — easy
Substance that loses oxygen or gains hydrogen during a redox reaction is said to be:
A. Oxidized
B. Reduced ✓ Correct
C. Oxidizing agent
D. Catalyst
Solution: Loss of oxygen or gain of hydrogen corresponds to reduction.
Q9 — easy
Black coating formed on silver articles when exposed to air for a long time is due to formation of:
A. Silver oxide
B. Silver sulphide (Ag₂S) ✓ Correct
C. Silver carbonate
D. Silver nitrate
Solution: Silver reacts with H₂S in air to form black silver sulphide.
Q10 — easy
To prevent rancidity in packaged potato chips, bags are flushed with unreactive gas:
A. Oxygen
B. Nitrogen ✓ Correct
C. Carbon dioxide
D. Hydrogen
Solution: Nitrogen provides an inert atmosphere that prevents oxidation of oils/fats.
Q11 — easy
Heating of ferrous sulphate crystals (FeSO₄·7H₂O) changes color from green to white, and on further heating produces gas with smell of burning sulphur:
A. SO₂ and SO₃ ✓ Correct
B. NO₂ and O₂
C. CO₂ and CO
D. H₂S and SO₂
Solution: FeSO₄ decomposes to Fe₂O₃ + SO₂ + SO₃.
Q12 — easy
Redox reaction is defined as a reaction in which:
A. Oxidation occurs only
B. Reduction occurs only
C. Oxidation and reduction occur simultaneously ✓ Correct
D. No heat is involved
Solution: Redox involves concurrent oxidation and reduction.
Q13 — easy
Respiration is considered an exothermic process because:
A. Heat is absorbed
B. Glucose combines with oxygen releasing energy ✓ Correct
C. Water evaporates
D. Oxygen is released
Solution: Cellular oxidation of glucose releases energy in the form of ATP and heat.
Q14 — easy
In equation: CuO + H₂ → Cu + H₂O, the reducing agent is:
A. CuO
B. H₂ ✓ Correct
C. Cu
D. H₂O
Solution: H₂ gains oxygen to form H₂O, acting as the reducing agent.
Q15 — easy
Insoluble solid formed during a double displacement reaction is called a:
A. Solute
B. Precipitate ✓ Correct
C. Solvent
D. Complex
Solution: An insoluble product separating from liquid is a precipitate.