CBSE Class 10 Science Chemical Reactions and Equations MCQs Set 12

Science Objective Questions and Answers: Chapter 01 Chemical Reactions and Equations

Explore reliable objective questions for Chapter 01 Chemical Reactions and Equations tailored for Class 10 learners. Utilizing these Science multiple-choice formats ensures thorough preparation and strengthens problem-solving speed for upcoming school assessments.

Download Chapter 01 Chemical Reactions and Equations MCQs with Answers

Navigate directly to the 50 objective questions for Chapter 01 Chemical Reactions and Equations using the digital viewer below. Each practice set includes verified answer keys, allowing students to instantly cross-check their work and identify areas requiring further revision.

This set of 35 Class 10 Science MCQs with answers focuses on displacement experiments, reactions of metals with acids and salt solutions, corrosion, rancidity, lime and whitewash, plus assertion and reason items. Each answer comes with a clear explanation and a short teacher's note.

Multiple Choice Questions

Question 1: What happens when dilute hydrochloric acid is added to iron filings? Tick the correct answer.
(a) Hydrogen gas and iron(II) chloride are produced
(b) Chlorine gas and ferric hydroxide are produced
(c) Heat is absorbed, i.e., the test tube becomes cold
(d) Iron salt and water are produced
Show Answer & Explanation

Answer: (a) Hydrogen gas and iron(II) chloride are produced

Explanation:
1. Fe + 2HCl → FeCl2 + H2
2. Iron is more reactive than hydrogen and displaces it from the acid.

Teacher's Note:
1. Metals above hydrogen react with dilute acids.
2. Iron forms the +2 chloride.

Question 2: What are 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
Show Answer & Explanation

Answer: (c) Fe(II) chloride and hydrogen gas

Explanation:
1. Fe + 2HCl → FeCl2 + H2
2. Iron forms the iron(II) salt and releases hydrogen.

Teacher's Note:
1. Dilute acids give Fe(II) salts with iron.
2. Hydrogen gas is evolved.

Question 3: Dilute hydrochloric acid is added to granulated zinc taken in a test tube. 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
Show Answer & Explanation

Answer: (d) A colourless and odourless gas is evolved

Explanation:
1. Zn + 2HCl → ZnCl2 + H2
2. Hydrogen is colourless and odourless and burns with a pop sound.

Teacher's Note:
1. The test tube also becomes warm.
2. Zinc chloride solution is colourless.

Question 4: A student added dilute HCl to a test tube containing zinc granules and made the following observations. Which one is correct?
(a) The zinc surface became dull and black
(b) A gas evolved which burns with a pop sound
(c) The solution turned yellow
(d) The solution becomes green in colour
Show Answer & Explanation

Answer: (b) A gas evolved which burns with a pop sound

Explanation:
1. Hydrogen gas is evolved and burns with a pop sound.
2. Zinc chloride solution is colourless, so (c) and (d) are wrong, and zinc does not turn black.

Teacher's Note:
1. Pop sound is the test for hydrogen.
2. Check each statement carefully.

Question 5: A dilute solution of sodium carbonate was added to two test tubes (A) containing dil. HCl and (B) containing dilute NaOH. The correct observation was
(a) a brown coloured gas liberated in test tube A
(b) a brown coloured gas liberated in test tube B
(c) a colourless gas liberated in test tube A
(d) a colourless gas liberated in test tube B
Show Answer & Explanation

Answer: (c) a colourless gas liberated in test tube A

Explanation:
1. Na2CO3 + 2HCl → 2NaCl + H2O + CO2: carbon dioxide is evolved in tube A.
2. Sodium carbonate does not react with NaOH, so tube B shows no gas.

Teacher's Note:
1. Carbonates give CO₂ with acids.
2. CO₂ is colourless.

Question 6: 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
Show Answer & Explanation

Answer: (c) lime water turns milky

Explanation:
1. Ca(OH)2 + CO2 → CaCO3 + H2O
2. Insoluble calcium carbonate makes the lime water milky.

Teacher's Note:
1. This is the test for carbon dioxide.
2. Excess CO₂ turns it clear again.

Question 7: Which of the following precipitates is formed when carbon dioxide gas is passed through lime water?
(a) Ca(OH)2
(b) Ca(OH)4
(c) CaCO3
(d) CaCO2
Show Answer & Explanation

Answer: (c) CaCO3

Explanation:
1. Lime water is calcium hydroxide and reacts with carbon dioxide.
2. Ca(OH)2 + CO2 → CaCO3 + H2O: calcium carbonate is the white precipitate.

Teacher's Note:
1. Check the valency of calcium (2) when writing formulae.
2. Calcium carbonate is CaCO₃.

Question 8: On immersing an iron nail in CuSO4 solution for a few minutes, you will observe
(a) no reaction takes place
(b) the colour of solution changes to green
(c) the surface of iron nails acquires a black coating
(d) the colour of solution fades away
Show Answer & Explanation

Answer: (b) the colour of solution changes to green

Explanation:
1. Fe + CuSO4 → FeSO4 + Cu
2. Blue copper sulphate is replaced by pale green iron(II) sulphate, and brown copper deposits on the nail.

Teacher's Note:
1. Iron is more reactive than copper.
2. Fe²⁺ solutions are pale green.

Question 9: What happens when a copper rod is dipped in iron sulphate solution?
(a) Copper displaces iron
(b) Blue colour of copper sulphate solution is obtained
(c) No reaction takes place
(d) Reaction is exothermic
Show Answer & Explanation

Answer: (c) No reaction takes place

Explanation:
1. Copper is less reactive than iron.
2. So copper cannot displace iron from iron sulphate and no reaction occurs.

Teacher's Note:
1. A metal displaces only less reactive metals from their salts.
2. Order: Zn > Fe > Cu.

Question 10: What happens when copper metal is dipped in the solution of zinc sulphate?
(a) Copper sulphate is formed
(b) Oxygen gas is formed
(c) Zinc metal is separated
(d) No reaction takes place
Show Answer & Explanation

Answer: (d) No reaction takes place

Explanation:
1. Zinc is more reactive than copper.
2. Copper cannot displace zinc, so no reaction takes place.

Teacher's Note:
1. Compare reactivity before predicting.
2. Zn is above Cu.

Question 11: What happens when zinc metal is dipped in the solution of copper sulphate?
(a) Zinc sulphate is formed
(b) Zinc oxide is formed
(c) Zinc sulphide is formed
(d) No reaction takes place
Show Answer & Explanation

Answer: (a) Zinc sulphate is formed

Explanation:
1. Zn + CuSO4 → ZnSO4 + Cu
2. Zinc displaces copper and forms zinc sulphate.

Teacher's Note:
1. The blue colour fades.
2. Copper deposits.

Question 12: Which metal is displaced when zinc metal is put in the solution of copper sulphate?
(a) Copper
(b) Zinc
(c) Sulphate
(d) All of the above
Show Answer & Explanation

Answer: (a) Copper

Explanation:
1. Zinc is more reactive and takes the place of copper.
2. Copper is displaced from its salt solution.

Teacher's Note:
1. Only metals can be displaced by metals.
2. Sulphate is an ion that stays in solution.

Question 13: Which metal is displaced when lead is put in the solution of copper chloride?
(a) Lead
(b) Copper
(c) Chlorine
(d) All of these
Show Answer & Explanation

Answer: (b) Copper

Explanation:
1. Pb + CuCl2 → PbCl2 + Cu
2. Lead is more reactive than copper, so copper is displaced.

Teacher's Note:
1. The more reactive metal goes into solution.
2. Lead is above copper.

Question 14: Which of the following is formed when lead metal reacts with the solution of copper chloride?
(a) No reaction takes place
(b) Chlorine gas
(c) Lead chloride
(d) Copper-lead complex
Show Answer & Explanation

Answer: (c) Lead chloride

Explanation:
1. Lead displaces copper from copper chloride.
2. Lead chloride is formed along with copper metal.

Teacher's Note:
1. The more reactive metal combines with the anion.
2. Copper is released.

Question 15: A student adds lead and silver to two different test tubes containing an equal amount of copper sulphate solution. The student observes that the colour of the solution in the test tube with lead changes. What explains the change in the colour of the solution?
(a) A displacement reaction takes place as lead replaces copper from the solution
(b) A decomposition reaction takes place as copper dissociates from sulphate
(c) A double displacement reaction takes place as copper dissociates from sulphate and lead combines with sulphate
(d) A combination reaction takes place as lead combines with sulphate
Show Answer & Explanation

Answer: (a) A displacement reaction takes place as lead replaces copper from the solution

Explanation:
1. Lead is more reactive than copper, so it takes copper's place.
2. Silver is less reactive, so no change is seen with silver.

Teacher's Note:
1. Compare lead and silver with copper in the reactivity series.
2. Only the more reactive metal reacts.

Question 16: Copper displaces which of the following metals from its salt solution?
(a) ZnSO4
(b) FeSO4
(c) AgNO3
(d) NiSO4
Show Answer & Explanation

Answer: (c) AgNO3

Explanation:
1. Copper is less reactive than Zn, Fe and Ni but more reactive than silver.
2. So only silver is displaced from AgNO3.

Teacher's Note:
1. Reactivity: Zn > Fe > Ni > Cu > Ag.
2. A metal displaces those below it.

Question 17: Which of the following reactions is not feasible?
(a) Aluminium + copper sulphate
(b) Zinc + copper sulphate solution
(c) Iron + copper sulphate solution
(d) Copper + zinc sulphate
Show Answer & Explanation

Answer: (d) Copper + zinc sulphate

Explanation:
1. Aluminium, zinc and iron are all more reactive than copper, so (a), (b) and (c) occur.
2. Copper is less reactive than zinc, so it cannot displace zinc from its salt solution and (d) does not occur.

Teacher's Note:
1. Check reactivity for each pair.
2. Copper is below zinc.

Question 18: Shashank was asked to carry out a displacement reaction which would show (i) formation of a colourless solution and (ii) black deposits. The reactants he should use are
(a) Fe(s) and Al2(SO4)3(aq)
(b) Al(s) and FeSO4(aq)
(c) Zn(s) and CuSO4(aq)
(d) Fe(s) and ZnSO4(aq)
Show Answer & Explanation

Answer: (b) Al(s) and FeSO4(aq)

Explanation:
1. Aluminium is more reactive than iron and displaces it from green FeSO4.
2. The solution becomes colourless Al2(SO4)3 and greyish-black iron is deposited.

Teacher's Note:
1. The metal added must be more reactive.
2. The green solution turns colourless.

Question 19: Four test tubes A, B, C and D contain Cu, Al, Fe and Zn respectively. If FeSO4 solution is added to the four test tubes, in which test tubes do we observe a black residue?
(a) A and B
(b) B and C
(c) A and C
(d) B and D
Show Answer & Explanation

Answer: (d) B and D

Explanation:
1. Al and Zn are more reactive than iron and displace it from FeSO4, giving a black iron residue.
2. Cu is less reactive and Fe is the same metal, so there is no reaction in A and C.

Teacher's Note:
1. Only more reactive metals displace iron.
2. Black residue is iron.

Question 20: Anivesha puts a zinc plate into a solution of copper sulphate kept in a glass container. She observes that the colour of the solution gets fainter with time, and after a few days she sees holes on the zinc plate. Which one of the following is NOT the reason for her observations?
(a) The blue colour of the copper sulphate solution changes to pale green
(b) Zinc displaces copper from its salt solution
(c) A single displacement reaction takes place
(d) A reddish-brown deposit is found on the zinc plate
Show Answer & Explanation

Answer: (a) The blue colour of the copper sulphate solution changes to pale green

Explanation:
1. Zn + CuSO4 → ZnSO4 + Cu: the blue colour fades to colourless because zinc sulphate is colourless.
2. A pale green colour is seen with iron, not zinc, so (a) is not a reason.

Teacher's Note:
1. Zinc sulphate is colourless.
2. Pale green indicates iron(II) ions.

Question 21: Zinc liberates hydrogen gas when reacted with dilute hydrochloric acid, whereas copper does not. This is because
(a) copper is more reactive than hydrogen
(b) copper is less reactive than hydrogen
(c) copper is a gas
(d) zinc is a non-metal
Show Answer & Explanation

Answer: (b) copper is less reactive than hydrogen

Explanation:
1. Metals above hydrogen in the reactivity series displace hydrogen from dilute acids.
2. Copper lies below hydrogen, so it does not.

Teacher's Note:
1. Compare with hydrogen in the series.
2. Zinc is above hydrogen.

Question 22: Which of the following reactions will evolve hydrogen gas with a pop sound?
(a) Concentrated nitric acid is reacted with sulphur
(b) A small piece of zinc is added to dilute hydrochloric acid
(c) Ammonia is passed over heated copper(II) oxide
(d) Lead nitrate is heated strongly in a test tube
Show Answer & Explanation

Answer: (b) A small piece of zinc is added to dilute hydrochloric acid

Explanation:
1. Zn + 2HCl → ZnCl2 + H2
2. Hydrogen burns with a pop sound; the other reactions do not give hydrogen.

Teacher's Note:
1. Metal + dilute acid gives hydrogen.
2. Pop sound identifies hydrogen.

Question 23: What is the characteristic of the gas evolved during the reaction of zinc with dilute sulphuric acid?
(a) Green in colour having a foul smell
(b) Colourless, odourless, and burns with a pop sound
(c) Red in colour having a sweet smell
(d) Colourless, pungent-smelling and burns with a pop sound
Show Answer & Explanation

Answer: (b) Colourless, odourless, and burns with a pop sound

Explanation:
1. Zn + H2SO4 → ZnSO4 + H2
2. Hydrogen is colourless and odourless and burns with a pop sound.

Teacher's Note:
1. Pungent smell would mean a different gas.
2. Hydrogen has no smell.

Question 24: Which is the correct observation for the reaction between granulated zinc and dilute hydrochloric acid?
(a) The reaction mixture turns milky
(b) Greenish-yellow gas is evolved
(c) The colourless and odourless gas evolves with a pop sound
(d) The surface of the metal turns shining
Show Answer & Explanation

Answer: (c) The colourless and odourless gas evolves with a pop sound

Explanation:
1. Hydrogen gas is released.
2. It is colourless and odourless and burns with a pop sound.

Teacher's Note:
1. The zinc surface does not shine; it dissolves slowly.
2. Pop sound is the test for hydrogen.

Question 25: Four students studied the reaction between solutions of BaCl2 and sodium sulphate. On mixing the two, they reported:
(a) The colour of the mixture became brown
(b) The solution forms separate layers
(c) A colourless mixture is obtained
(d) A white substance settles at the bottom
Show Answer & Explanation

Answer: (d) A white substance settles at the bottom

Explanation:
1. BaCl2 + Na2SO4 → BaSO4 + 2NaCl
2. Barium sulphate is a white insoluble solid that settles at the bottom.

Teacher's Note:
1. A precipitate settles; there are no layers.
2. BaSO₄ is white.

Question 26: Which of the following gases can be used for storage of a fresh sample of an oil for a long time?
(a) Carbon dioxide or oxygen
(b) Nitrogen or helium
(c) Helium or oxygen
(d) Nitrogen or oxygen
Show Answer & Explanation

Answer: (b) Nitrogen or helium

Explanation:
1. Oxygen would oxidise the oil, so it must be avoided.
2. Nitrogen and helium are inert and do not react with oils.

Teacher's Note:
1. Use an inert atmosphere to prevent oxidation.
2. Both nitrogen and helium are unreactive.

Question 27: Fatty foods become rancid due to the process of
(a) reduction
(b) corrosion
(c) oxidation
(d) hydrogenation
Show Answer & Explanation

Answer: (c) oxidation

Explanation:
1. When fats and oils are exposed to air they are oxidised.
2. The products have a bad smell and taste, which is rancidity.

Teacher's Note:
1. Rancid food has changed smell and taste.
2. Antioxidants slow the process.

Question 28: Rancidity can be prevented by
(a) adding antioxidants
(b) storing food away from light
(c) keeping food in a refrigerator
(d) all of these
Show Answer & Explanation

Answer: (d) all of these

Explanation:
1. Antioxidants, storing away from light and refrigeration all slow oxidation of fats.
2. So all the methods listed help.

Teacher's Note:
1. Also pack in nitrogen or in air-tight containers.
2. Low temperature slows oxidation.

Question 29: How can rancidity be prevented?
(a) By adding antioxidants in food
(b) By adding more oxygen to food
(c) By keeping food items in the open
(d) All of the above
Show Answer & Explanation

Answer: (a) By adding antioxidants in food

Explanation:
1. Antioxidants are oxidised in preference to fats and oils, so the food does not turn rancid.
2. Adding oxygen or keeping food open would speed up oxidation.

Teacher's Note:
1. Prevent contact with oxygen.
2. Antioxidants are added in small amounts.

Question 30: Which of the following is termed as rancidity?
(a) Reduction of oxygen present in food
(b) Oxidation of oil present in food
(c) Oxidation of sugar present in food
(d) All of the above
Show Answer & Explanation

Answer: (b) Oxidation of oil present in food

Explanation:
1. Rancidity is the oxidation of fats and oils in food.
2. It changes the smell and taste.

Teacher's Note:
1. Rancidity affects fats and oils, not sugars.
2. It happens faster in warm weather.

Question 31: A substance added to food containing fats and oils is called
(a) oxidant
(b) rancid
(c) coolant
(d) antioxidant
Show Answer & Explanation

Answer: (d) antioxidant

Explanation:
1. Antioxidants are added to prevent the oxidation of fats and oils.
2. This keeps the food from becoming rancid.

Teacher's Note:
1. BHA and BHT are common antioxidants.
2. Anti means against.

Assertion–Reason Questions

Question 32:
Assertion (A): Rusting of iron is endothermic in nature.
Reason (R): As the reaction is slow, the release of heat is barely evident.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (d) A is false, but R is true.

Explanation:
1. A is false: rusting is exothermic.
2. R is true: the heat is released so slowly that it is hardly noticed.

Teacher's Note:
1. Slow reactions can still be exothermic.
2. Rusting is slow oxidation.

Question 33:
Assertion (A): When a copper strip is placed in ferrous sulphate solution, the colour of the solution changes.
Reason (R): Iron is more reactive than copper.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (d) A is false, but R is true.

Explanation:
1. A is false: copper cannot displace iron, so there is no change.
2. R is true: iron is more reactive than copper.

Teacher's Note:
1. No reaction means no colour change.
2. Iron is above copper.

Question 34:
Assertion (A): Corrosion of iron is a serious problem.
Reason (R): Every year an enormous amount of money is spent to replace damaged iron.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (a) Both A and R are true, and R is the correct explanation of A.

Explanation:
1. Both statements are true.
2. The huge cost of replacement is the reason corrosion is a serious problem.

Teacher's Note:
1. Corrosion weakens bridges, ships and railings.
2. Prevention saves money.

Question 35:
Assertion (A): Copper vessels get covered with a green coating in the rainy season.
Reason (R): It is because of the formation of copper carbonate.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (a) Both A and R are true, and R is the correct explanation of A.

Explanation:
1. Both statements are true: copper reacts with moist air to form basic copper carbonate.
2. The green coating is this carbonate, so R explains A.

Teacher's Note:
1. Corrosion of copper is green.
2. It involves CO₂, O₂ and moisture.

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Multiple Choice Questions (MCQs) for Class 10 Science Chapter 01 Chemical Reactions and Equations

Class 10 Science Chapter 01 Chemical Reactions and Equations Objective Test Questions

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