Question

Solubility of CaO in water is:

• A. Chermic
• B. Endothermic
• C. Exothermic
• D. Hypothermic

Hint:

Exothermic reactions release heat, and the dissolution of CaO in water is an example of such a reaction.

Answer 1

The Correct Option is C

Solubility of CaO in water is: 

• Option 1: Chermic - This is not a correct term related to solubility or dissolution processes. It appears to be a typographical error.
• Option 2: Endothermic - This is incorrect. An endothermic process absorbs heat, but the dissolution of CaO in water releases heat.
• Option 3: Exothermic - This is the correct answer. When calcium oxide (CaO) dissolves in water, it reacts exothermically, releasing a significant amount of heat and forming calcium hydroxide (Ca(OH)2).
• Option 4: Hypothermic - This is not a recognized term in chemistry related to the dissolution process.

Explanation:

The dissolution of calcium oxide (CaO) in water is an exothermic process, meaning that it releases heat. The reaction produces calcium hydroxide (Ca(OH)2) and is highly exothermic, making it feel hot to the touch.

Answer 2

When calcium oxide dissolves in water it does not just physically disperse, it reacts chemically to form calcium hydroxide. The heat change of that reaction decides the answer, so let's write the reaction and check each option against it.

1. Chermic: This is not a real thermodynamic term at all, so it cannot describe any heat change.
2. Endothermic: An endothermic process would need to absorb heat from the surroundings, which would make the container feel cold. That is the opposite of what actually happens when CaO meets water.
3. Exothermic: The reaction CaO + H2O to Ca(OH)2 breaks the ionic lattice of CaO and forms new O-H bonds in Ca(OH)2 while releasing a large amount of heat, enough to make the mixture noticeably hot. This matches the observed behaviour.
4. Hypothermic: This word describes a drop in body temperature in medicine, not a chemical process, so it does not apply here.

Because the reaction gives out heat rather than taking it in, the dissolution of CaO in water is exothermic.

So the correct answer is Exothermic.