Combination and Decomposition Reactions MCQs

Q1. What is the name of the reaction in which a single reactant breaks down to give simpler products?

• A.Combination reaction
• B.Exothermic reaction
• C.Decomposition reaction
• D.Endothermic reaction

Answer: C. Decomposition reaction

Eliminate first - option A) 'Combination reaction' is incorrect: Combination reaction involves two or more substances combining to form a single product; option B) 'Exothermic reaction' doesn't hold - Exothermic reaction involves heat being released along with the formation of products; option D) 'Endothermic reaction' is incorrect: Endothermic reaction involves heat being absorbed during the reaction. That leaves only option C). Confirm with the chapter rule: Decomposition reaction involves a single reactant breaking down to give simpler products (chemistry, chapter 'Chemical Reactions and Equations'). Answer: C) Decomposition reaction.

Q2. The decomposition reaction of silver chloride is caused by which form of energy?

• A.Heat
• B.Light
• C.Electricity
• D.Mechanical energy

Answer: B. Light

Concept involved: The reaction is caused by sunlight. Translating to the choices: The reaction is caused by sunlight, which provides the energy needed for decomposition. Ruling out the other options: option A) 'Heat' is wrong because The reaction is caused by sunlight, not heat; option C) 'Electricity' doesn't hold - The reaction is caused by sunlight, not electricity; option D) 'Mechanical energy' doesn't hold - The reaction is caused by sunlight, not mechanical energy. Putting it together the correct option is B) Light.

Q3. Which of the following is a decomposition reaction (NCERT)?

• A.2FeSO4 --heat--> Fe2O3 + SO2 + SO3
• B.Zn + CuSO4 -> ZnSO4 + Cu
• C.NaOH + HCl -> NaCl + H2O
• D.CaO + H2O -> Ca(OH)2

Answer: A. 2FeSO4 --heat--> Fe2O3 + SO2 + SO3