Chemical Reactions & Equations
1. A chemical equation is balanced to satisfy which law?
Correct Answer: b) Law of Conservation of Mass
Matter can neither be created nor destroyed. Therefore, the number of atoms on the reactant side must equal the product side.
Matter can neither be created nor destroyed. Therefore, the number of atoms on the reactant side must equal the product side.
2. The reaction in which a single substance breaks down into two or more simpler substances is called:
Correct Answer: b) Decomposition Reaction
Example: Heating Calcium Carbonate (CaCO3) to form Calcium Oxide (CaO) and Carbon Dioxide (CO2).
Example: Heating Calcium Carbonate (CaCO3) to form Calcium Oxide (CaO) and Carbon Dioxide (CO2).
3. When Magnesium ribbon is burnt in air, the ash formed is:
Correct Answer: b) White
Magnesium burns with a dazzling white flame to form a white powder called Magnesium Oxide (MgO).
Magnesium burns with a dazzling white flame to form a white powder called Magnesium Oxide (MgO).
4. What is the chemical formula of Rust?
Correct Answer: c) Fe2O3.xH2O
Rust is hydrated iron(III) oxide.
Rust is hydrated iron(III) oxide.
5. Which gas is used to flush bags of potato chips to prevent rancidity?
Correct Answer: b) Nitrogen
Nitrogen is an inert gas that prevents the oxidation of oils and fats in the chips.
Nitrogen is an inert gas that prevents the oxidation of oils and fats in the chips.
6. Respiration is an example of which type of reaction?
Correct Answer: a) Exothermic reaction
Respiration releases energy (heat) by breaking down glucose, hence it is exothermic.
Respiration releases energy (heat) by breaking down glucose, hence it is exothermic.
7. When Iron nails are dipped in Copper Sulphate solution, the colour changes from:
Correct Answer: b) Blue to Pale Green
Iron displaces Copper to form Ferrous Sulphate (Green), removing the blue color of Copper Sulphate.
Iron displaces Copper to form Ferrous Sulphate (Green), removing the blue color of Copper Sulphate.
8. A reaction in which heat is absorbed is called:
Correct Answer: b) Endothermic
Endothermic reactions require energy input (heat, light, or electricity) to proceed.
Endothermic reactions require energy input (heat, light, or electricity) to proceed.
9. Oxidation involves:
Correct Answer: b) Gain of Oxygen or Loss of Hydrogen
Oxidation is defined as the addition of oxygen, removal of hydrogen, or loss of electrons.
Oxidation is defined as the addition of oxygen, removal of hydrogen, or loss of electrons.
10. Pb(NO3)2 + 2KI → PbI2 + 2KNO3. The precipitate (PbI2) formed in this reaction is of which colour?
Correct Answer: a) Yellow
Lead Iodide (PbI2) forms a distinct yellow precipitate. This is a Double Displacement reaction.
Lead Iodide (PbI2) forms a distinct yellow precipitate. This is a Double Displacement reaction.
11. Which chemical is used in Black and White photography?
Correct Answer: a) Silver Chloride (AgCl)
Also Silver Bromide (AgBr). They undergo photolytic decomposition in light.
Also Silver Bromide (AgBr). They undergo photolytic decomposition in light.
12. The reaction between an acid and a base to give a salt and water is known as:
Correct Answer: c) Neutralization reaction
Example: HCl + NaOH → NaCl + H2O.
Example: HCl + NaOH → NaCl + H2O.
13. In the reaction CuO + H2 → Cu + H2O, the oxidizing agent is:
Correct Answer: a) CuO
CuO loses oxygen (is reduced), therefore it acts as the oxidizing agent.
CuO loses oxygen (is reduced), therefore it acts as the oxidizing agent.
14. The symbol ‘(aq)’ in a chemical equation represents:
Correct Answer: d) Aqueous solution (in water)
It indicates the reactant or product is dissolved in water.
It indicates the reactant or product is dissolved in water.
15. Electrolysis of water is a decomposition reaction. The molar ratio of Hydrogen and Oxygen gas liberated is:
Correct Answer: b) 2:1
Water is H2O. When broken down, it produces 2 volumes of Hydrogen for every 1 volume of Oxygen.
Water is H2O. When broken down, it produces 2 volumes of Hydrogen for every 1 volume of Oxygen.
16. What is the chemical formula of Quicklime?
Correct Answer: b) CaO
Calcium Oxide is Quicklime. Calcium Hydroxide Ca(OH)2 is Slaked Lime.
Calcium Oxide is Quicklime. Calcium Hydroxide Ca(OH)2 is Slaked Lime.
17. Which of the following is a Displacement reaction?
Correct Answer: c) Zn + CuSO4 → ZnSO4 + Cu
Zinc is more reactive than Copper and displaces it from its salt solution.
Zinc is more reactive than Copper and displaces it from its salt solution.
18. Which gas burns with a ‘Pop’ sound?
Correct Answer: b) Hydrogen
When a burning candle is brought near Hydrogen gas, it burns with a characteristic pop sound.
When a burning candle is brought near Hydrogen gas, it burns with a characteristic pop sound.
19. Fatty foods become rancid due to the process of:
Correct Answer: a) Oxidation
Microbial oxidation of fats and oils creates foul smell and taste.
Microbial oxidation of fats and oils creates foul smell and taste.
20. An unbalanced chemical equation is also known as:
Correct Answer: b) Skeletal Equation
A skeletal equation shows the formulas of reactants and products but does not indicate their relative amounts (it is not balanced).
A skeletal equation shows the formulas of reactants and products but does not indicate their relative amounts (it is not balanced).