When calcium oxide is mixed with water, heat is released. Based on the heat change, what type of reaction is this?
Answer and explanation
Correct answer: Exothermic reaction
Calcium oxide reacts with water to form calcium hydroxide: CaO + H₂O → Ca(OH)₂ + heat. The important evidence is that heat is released and the mixture becomes warm, so the reaction is exothermic and option A is correct. An endothermic reaction would absorb heat and cool the surroundings. The light-driven and electricity-driven decomposition choices do not describe this heat-releasing reaction.
Frequently asked questions
What is the correct answer to this question?
Exothermic reaction
Why is this the correct answer?
Calcium oxide reacts with water to form calcium hydroxide: CaO + H₂O → Ca(OH)₂ + heat. The important evidence is that heat is released and the mixture becomes warm, so the reaction is exothermic and option A is correct. An endothermic reaction would absorb heat and cool the surroundings. The light-driven and electricity-driven decomposition choices do not describe this heat-releasing reaction.
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.
