Question

Sublimation is regarded as a chemical change but the slaking lime is considered a physical change.

Answer 1

Hint: Sublimation includes change of solid substance to its vapour state and slaking of lime means adding water to the lime. This reaction is to be written which leads you to the correct answer.

Complete Solution :
In our previous classes of chemistry, we have studied about the concepts of inorganic chemistry which deals with the facts about the conversion of one compound to another by the hydration process, heating or even by reduction.
Now let us see what are the physical and chemical changes that undergo in the given particular reaction.
- Sublimation is a type of the transition in phase or state of matter that is the same like melting, freezing and evaporation.
- Here, in this process one state of matter that is for instance solid undergoes a change in its physical state and turns to be liquid and which in turn can change into gaseous form.
- Therefore, sublimation is the physical change.
- On the other hand, slaking is the process of adding water which changes the original products in the form of hydroxides.
- Slaking of lime thus includes treatment of lime that has a molecular formula $CaO$ with that of water which turns the lime into calcium hydroxide. The reaction is as shown below,
\[CaO+{{H}_{2}}O\to Ca{{(OH)}_{2}}\] with the release of some amount of energy. This process is therefore an exothermic process.

- Here, in this process there is chemical change and this change cannot be reversed in any form by the changes in physical things.
- Therefore, this is the reason that sublimation is regarded as the physical change and slaking of lime is considered a chemical change.
Thus, the correct answer will be that the given statement is false.

Note: Read the question carefully before answering because sometimes confusion may occur between physical and chemical changes and the statement in the question seems to be true. Therefore, check prior answers which substance will go chemical change and which will go physical change and answer accordingly.