When water is added to calcium oxide, the container becomes hot. What does this indicate about the reaction?
Answer and explanation
Correct answer: It is an exothermic combination reaction
Calcium oxide reacts with water to form calcium hydroxide: \(\mathrm{CaO + H_2O \rightarrow Ca(OH)_2}\). Heat is released during this reaction, so the container becomes hot. Since two reactants combine to form one product, it is a combination reaction; because heat is released, it is exothermic. In contrast, a decomposition reaction involves one compound breaking down into two or more substances.
Frequently asked questions
What is the correct answer to this question?
It is an exothermic combination reaction
Why is this the correct answer?
Calcium oxide reacts with water to form calcium hydroxide: \(\mathrm{CaO + H_2O \rightarrow Ca(OH)_2}\). Heat is released during this reaction, so the container becomes hot. Since two reactants combine to form one product, it is a combination reaction; because heat is released, it is exothermic. In contrast, a decomposition reaction involves one compound breaking down into two or more substances.
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.
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