When water is added to calcium oxide, the container becomes hot. Which conclusion is correct from this observation?
Answer and explanation
Correct answer: Heat was released in the reaction.
A hot container shows that heat is released to the surroundings during the reaction, so it is an exothermic reaction. Calcium oxide reacts with water to form calcium hydroxide: \(\mathrm{CaO + H_2O \rightarrow Ca(OH)_2 + heat}\). It is not merely a physical change because a new substance, calcium hydroxide, is formed.
Frequently asked questions
What is the correct answer to this question?
Heat was released in the reaction.
Why is this the correct answer?
A hot container shows that heat is released to the surroundings during the reaction, so it is an exothermic reaction. Calcium oxide reacts with water to form calcium hydroxide: \(\mathrm{CaO + H_2O \rightarrow Ca(OH)_2 + heat}\). It is not merely a physical change because a new substance, calcium hydroxide, is formed.
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.
