Combination Reaction MCQs Quiz | Class 10
This Science (Code 086) quiz covers Class X Unit I: Chemical Substances – Nature and Behaviour, focusing specifically on Combination Reactions. The questions test your understanding of definitions, identification of reaction types, and specific examples like the formation of slaked lime and burning of coal. Attempt all 10 MCQs, check your score, and download the detailed answer PDF for revision.
Overview of Combination Reactions
A combination reaction is a type of chemical reaction where two or more reactants combine to form a single product. It is one of the most fundamental types of reactions in chemistry. The general form of this reaction is A + B -> AB. These reactions are often exothermic, meaning they release heat into the surroundings.
Key Characteristics
- Single Product: Regardless of the number of reactants, only one new substance is formed.
- Reactants: Can be elements or compounds.
- Energy Change: Most combination reactions involve the release of heat (exothermic), though some may require heat.
Common Examples
| Reaction Name | Equation | Description |
|---|---|---|
| Burning of Coal | C + O2 -> CO2 | Carbon combines with oxygen to form carbon dioxide. |
| Formation of Water | 2H2 + O2 -> 2H2O | Hydrogen gas reacts with oxygen gas to produce water. |
| Slaking of Lime | CaO + H2O -> Ca(OH)2 | Quick lime reacts vigorously with water to form slaked lime and heat. |
Quick Revision Notes
- Calcium Oxide (CaO): Known as Quick Lime. Used in cement manufacturing.
- Calcium Hydroxide (Ca(OH)2): Known as Slaked Lime. Used for whitewashing walls. It reacts with CO2 in the air to form a shiny layer of Calcium Carbonate (CaCO3).
- Magnesium Ribbon: Burns with a dazzling white flame to form white powder (Magnesium Oxide, MgO).
Extra Practice Questions
- What is the chemical formula for Quick Lime? (Ans: CaO)
- Is the burning of natural gas a combination reaction? (Ans: It is an exothermic reaction, but technically a combustion reaction often producing multiple products like CO2 and H2O, so strict combination depends on perspective, but usually classified under combustion/oxidation).
- What forms when iron powder and sulfur are heated together? (Ans: Iron(II) sulfide, FeS).
- Why do walls shine after whitewashing? (Ans: Formation of Calcium Carbonate).
- Write the product of H2 + Cl2 in sunlight. (Ans: 2HCl).
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