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First read the questions carefully using the Read section. Use the Details button to understand concepts clearly. After completing reading, click Practice Quiz to test yourself.
📘 Study MCQs
Q1. What happens to iron articles when left exposed for some time?
• They become shinier.
• They get coated with a reddish-brown powder.
• They turn silver in color.
• They become magnetic.
Answer: They get coated with a reddish-brown powder.
The text states that new, shiny iron articles get coated with a reddish-brown powder over time, which is rust.
Q2. What is the common name for the process where iron gets coated with a reddish-brown powder?
• Galvanization
• Rancidity
• Rusting
• Tarnishing
Answer: Rusting
This process is commonly known as the rusting of iron.
Q3. What is the general term for the process where a metal is attacked by moisture, acids, etc.?
• Reduction
• Oxidation
• Corrosion
• Displacement
Answer: Corrosion
When a metal is attacked by substances around it, it is said to corrode, and the process is called corrosion.
Q4. What color coating is formed on copper due to corrosion?
• Reddish-brown
• Black
• White
• Green
Answer: Green
The green coating on copper is given as an example of corrosion.
Q5. What color coating is formed on silver due to corrosion?
• Green
• White
• Black
• Blue
Answer: Black
The black coating on silver is given as an example of corrosion.
Q6. Which of the following objects is specifically mentioned as being damaged by corrosion?
• Plastic chairs
• Wooden doors
• Car bodies and bridges
• Glass windows
Answer: Car bodies and bridges
Corrosion causes damage to car bodies, bridges, iron railings, ships, and all objects made of metals.
Q7. What is a serious economic problem mentioned regarding corrosion?
• It makes metals stronger.
• An enormous amount of money is spent to replace damaged iron.
• It improves the appearance of metals.
• It creates new jobs in painting.
Answer: An enormous amount of money is spent to replace damaged iron.
The text states that corrosion of iron is a serious problem, and every year a huge amount of money is spent to replace damaged iron.
Q8. What happens to fats and oils when they are oxidised?
• They become more nutritious.
• They become rancid.
• They solidify.
• They become sweeter.
Answer: They become rancid.
When fats and oils are oxidised, they become rancid, and their smell and taste change.
Q9. What is the change associated with rancid food?
• Change in color only
• Change in smell and taste
• Increase in weight
• Becoming more crispy
Answer: Change in smell and taste
Rancidity is characterized by a change in the smell and taste of the food containing fats and oils.
Q10. What are substances called that prevent oxidation in food?
• Preservatives
• Catalysts
• Antioxidants
• Reducing agents
Answer: Antioxidants
Substances that prevent oxidation are added to foods and are called antioxidants.
Q11. How does keeping food in airtight containers help?
• It speeds up oxidation.
• It slows down oxidation.
• It makes food cook faster.
• It adds flavor.
Answer: It slows down oxidation.
Keeping food in airtight containers helps to slow down oxidation by limiting contact with air.
Q12. Which gas do chips manufacturers flush into bags to prevent oxidation?
• Oxygen
• Carbon dioxide
• Hydrogen
• Nitrogen
Answer: Nitrogen
Chips manufacturers flush bags of chips with gas such as nitrogen to prevent them from getting oxidised.
Q13. What is the primary reason for flushing chips bags with nitrogen?
• To add weight
• To prevent chips from getting oxidised
• To improve taste
• To make them appear fresh
Answer: To prevent chips from getting oxidised
Nitrogen is inert and displaces oxygen, preventing the oxidation (rancidity) of fats in the chips.
Q14. According to the summary, what must a complete chemical equation represent?
• Only the products
• The reactants, products, and their physical states
• Only the reaction conditions
• The speed of the reaction
Answer: The reactants, products, and their physical states
A complete chemical equation represents the reactants, products, and their physical states symbolically.
Q15. Why must a chemical equation always be balanced?
• To make it look neat
• So that the number of atoms of each type is the same on both sides
• To include the reaction temperature
• To write it in a shorter form
Answer: So that the number of atoms of each type is the same on both sides
An equation is balanced so that the numbers of atoms of each type are the same on the reactant and product sides, obeying the law of conservation of mass.
Q16. In which reaction do two or more substances combine to form a new single substance?
• Decomposition reaction
• Displacement reaction
• Combination reaction
• Double displacement reaction
Answer: Combination reaction
In a combination reaction, two or more substances combine to form a new single substance.
Q17. What type of reaction is the opposite of a combination reaction?
• Displacement
• Double displacement
• Decomposition
• Oxidation
Answer: Decomposition
Decomposition reactions are opposite to combination reactions. A single substance breaks down.
Q18. In a decomposition reaction, what happens?
• Two substances combine.
• A single substance decomposes into two or more substances.
• Ions are exchanged.
• An element is displaced.
Answer: A single substance decomposes into two or more substances.
In a decomposition reaction, a single substance decomposes to give two or more substances.
Q19. What are reactions called in which heat is given out along with the products?
• Endothermic
• Exothermic
• Thermal
• Photolytic
Answer: Exothermic
Reactions in which heat is given out along with the products are called exothermic reactions.
Q20. What are reactions called in which heat is absorbed?
• Exothermic
• Endothermic
• Combustion
• Redox
Answer: Endothermic
Reactions in which heat is absorbed are known as endothermic reactions.
Q21. What occurs in a displacement reaction?
• Two compounds exchange ions.
• An element displaces another element from its compound.
• A single compound breaks down.
• Two elements combine.
Answer: An element displaces another element from its compound.
When an element displaces another element from its compound, a displacement reaction occurs.
Q22. What is exchanged in a double displacement reaction?
• Heat only
• Two different atoms or groups of atoms (ions)
• Only electrons
• Oxygen atoms only
Answer: Two different atoms or groups of atoms (ions)
Two different atoms or groups of atoms (ions) are exchanged in double displacement reactions.
Q23. What do precipitation reactions produce?
• Gases
• Insoluble salts
• Heat and light
• Soluble compounds
Answer: Insoluble salts
Precipitation reactions produce insoluble salts, which appear as a precipitate.
Q24. According to the summary, what is oxidation defined as?
• Loss of oxygen or gain of hydrogen
• Gain of oxygen or loss of hydrogen
• Loss of electrons only
• Gain of electrons only
Answer: Gain of oxygen or loss of hydrogen
Oxidation is the gain of oxygen or loss of hydrogen by a substance.
Q25. According to the summary, what is reduction defined as?
• Gain of oxygen or loss of hydrogen
• Loss of oxygen or gain of hydrogen
• Loss of electrons only
• Gain of heat
Answer: Loss of oxygen or gain of hydrogen
Reduction is the loss of oxygen or gain of hydrogen by a substance.
Q26. What happens to silver chloride when placed in sunlight?
• It melts.
• It turns white.
• It turns grey.
• It dissolves.
Answer: It turns grey.
White silver chloride turns grey in sunlight due to decomposition into silver and chlorine.
Q27. What causes the decomposition of silver chloride?
• Heat
• Electricity
• Light (Sunlight)
• Pressure
Answer: Light (Sunlight)
The decomposition is caused by sunlight, as indicated by the equation and the statement “Silver chloride turns grey in sunlight.”
Q28. What are the products of the decomposition of silver chloride in sunlight?
• Silver and chlorine gas
• Silver oxide and chlorine
• Silver and oxygen
• Silver chloride and light
Answer: Silver and chlorine gas
The reaction is: 2AgCl(s) → 2Ag(s) + Cl₂(g). The products are silver (Ag) and chlorine gas (Cl₂).
Q29. Which compound behaves similarly to silver chloride in sunlight?
• Silver iodide
• Silver bromide
• Silver oxide
• Silver nitrate
Answer: Silver bromide
The text states: “Silver bromide also behaves in the same way,” decomposing to silver and bromine in sunlight.
Q30. Where is the decomposition reaction of silver salts used?
• In cooking
• In black and white photography
• In making alloys
• In water purification
Answer: In black and white photography
The above reactions (of AgCl and AgBr) are used in black and white photography.
Q31. What form of energy causes the decomposition of silver chloride and silver bromide?
• Heat energy
• Electrical energy
• Light energy
• Sound energy
Answer: Light energy
Sunlight (light energy) causes these decomposition reactions.
Q32. Decomposition reactions require energy in the form of:
• Heat, light, or electricity
• Only pressure
• Only sound
• Only catalysts
Answer: Heat, light, or electricity
The decomposition reactions require energy either in the form of heat, light, or electricity for breaking down the reactants.
Q33. What type of reaction is the decomposition of silver chloride in terms of heat change?
• Exothermic
• Endothermic
• Neutral
• Combustion
Answer: Endothermic
Reactions in which heat is absorbed are endothermic. The decomposition requires light energy, which is absorbed.
Q34. In the reaction Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s), what is observed?
• The iron nail becomes shiny.
• The blue color of copper sulfate fades, and the nail gets a brownish coating.
• The solution turns red.
• A white precipitate forms.
Answer: The blue color of copper sulfate fades, and the nail gets a brownish coating.
The iron nail becomes brownish (due to copper coating), and the blue color of copper sulfate solution fades as it turns into greenish iron sulfate.
Q35. What type of reaction is Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s)?
• Combination
• Decomposition
• Displacement
• Double displacement
Answer: Displacement
Iron displaces copper from copper sulfate. This is known as a displacement reaction.
Q36. In the displacement reaction, which element is displaced by iron?
• Sulfur
• Oxygen
• Copper
• Iron itself
Answer: Copper
Iron displaces or removes copper from copper sulfate solution.
Q37. Which of the following is another example of a displacement reaction?
• Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)
• NaCl(aq) + AgNO₃(aq) → AgCl(s) + NaNO₃(aq)
• CaCO₃(s) → CaO(s) + CO₂(g)
• CH₄ + 2O₂ → CO₂ + 2H₂O
Answer: Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)
This is given as another example where zinc displaces copper, similar to the iron reaction.
Q38. Why can zinc displace copper from its compound?
• Zinc is less reactive than copper.
• Zinc is more reactive than copper.
• Zinc has the same reactivity as copper.
• Zinc is a noble metal.
Answer: Zinc is more reactive than copper.
Zinc and lead are stated to be more reactive elements than copper, so they can displace copper from its compounds.
Q39. What is the color of copper sulfate solution?
• Colorless
• Green
• Blue
• Brown
Answer: Blue
The text refers to the “blue colour of copper sulphate solution” which fades during the displacement reaction.
Q40. What is the brownish coating that forms on the iron nail?
• Iron oxide (rust)
• Copper metal
• Iron sulfate
• Copper oxide
Answer: Copper metal
The displaced copper from copper sulfate deposits on the iron nail, giving it a brownish coating.
Q41. What is the energy requirement for endothermic reactions?
• They release heat.
• They absorb heat.
• They release light.
• They occur without any energy.
Answer: They absorb heat.
Endothermic reactions are those in which heat is absorbed from the surroundings.
Q42. Based on the text, what is the result of mixing barium hydroxide and ammonium chloride likely to be?
• An exothermic reaction (test tube feels hot)
• An endothermic reaction (test tube feels cold)
• A precipitation reaction
• A color change
Answer: An endothermic reaction (test tube feels cold)
The activity asks what you feel when you touch the test tube and whether it is exothermic or endothermic. Mixing these typically causes an endothermic reaction, making the test tube feel cold.
Q43. What is the main takeaway regarding the energy for decomposition reactions?
• They always give out energy.
• They always require an input of energy.
• They never involve energy changes.
• They only occur in sunlight.
Answer: They always require an input of energy.
Decomposition reactions require energy (heat, light, or electricity) to break down the reactants.
Q44. In the context of the text, what does “tarnished” mean for metals?
• Becoming shiny
• Losing luster and developing a coating
• Melting
• Becoming magnetic
Answer: Losing luster and developing a coating
Some metals get tarnished, meaning they lose their shine and develop a coating, similar to corrosion.
Q45. What is the common factor between rancidity and corrosion?
• Both involve loss of hydrogen.
• Both are caused by oxidation reactions.
• Both make substances stronger.
• Both are desirable processes.
Answer: Both are caused by oxidation reactions.
Corrosion of metals and rancidity of fats are both undesirable effects caused by oxidation (reaction with oxygen).
Q46. According to the learnt points, what is always true for a balanced chemical equation?
• It has more products than reactants.
• The mass of reactants is greater than products.
• The number of atoms of each element is the same on both sides.
• It only contains gaseous products.
Answer: The number of atoms of each element is the same on both sides.
A chemical equation is balanced so that the numbers of atoms of each type are equal on the reactant and product sides.
Q47. What is the visual evidence that a displacement reaction has occurred between iron and copper sulfate?
• Formation of a gas
• Change in color of the solution and the metal
• Formation of a pungent smell
• The solution becomes hotter
Answer: Change in color of the solution and the metal
The blue color fades, and the iron nail gets a brownish coating, indicating the reaction.
Q48. What is the purpose of adding antioxidants to food?
• To make it taste sour
• To prevent oxidation and rancidity
• To increase its fat content
• To change its color
Answer: To prevent oxidation and rancidity
Antioxidants are added to prevent oxidation, which in turn prevents fats and oils from becoming rancid.
Q49. Which of the following is NOT listed as a form of energy that can cause decomposition?
• Heat
• Light
• Electricity
• Sound
Answer: Sound
The text specifies that decomposition reactions require energy in the form of heat, light, or electricity.
Q50. Based on the summary, which statement correctly describes a double displacement reaction?
• One element replaces another.
• Two compounds exchange ions to form two new compounds.
• A single compound breaks down.
• Two elements combine.
Answer: Two compounds exchange ions to form two new compounds.
In double displacement reactions, two different atoms or groups of atoms (ions) are exchanged between two reactants.