What type of reaction occurs when water is added to quicklime, CaO, to form calcium hydroxide?
Answer and explanation
Correct answer: Combination reaction
The reaction is \(CaO + H_2O \rightarrow Ca(OH)_2\). Two reactants, quicklime and water, combine to form only one product, calcium hydroxide; therefore it is a combination reaction. The number of products is the useful test here. It is not decomposition because nothing breaks apart, not displacement because no element replaces another, and not double displacement because two ionic compounds do not exchange ions.
Frequently asked questions
What is the correct answer to this question?
Combination reaction
Why is this the correct answer?
The reaction is \(CaO + H_2O \rightarrow Ca(OH)_2\). Two reactants, quicklime and water, combine to form only one product, calcium hydroxide; therefore it is a combination reaction. The number of products is the useful test here. It is not decomposition because nothing breaks apart, not displacement because no element replaces another, and not double displacement because two ionic compounds do not exchange ions.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Chemical Reactions and Equations.
