Question

Which answer below correctly identifies the type of change and the explanation for the mixture of calcium corbonate and hydrochloric acid?
Physical change because even though gas formation was observed, the calcium carbonate retained its original properties.
Physical change because even though a particle size change was observed, the calcium retained its original properties.
Chemical change because gas formation was observed, which indicated that the calcium carbonate was transformed into a different substance.
Chemical change because a particle size change was observed, which indicated that the calcium carbonate was transformed into a different substance.

Answer 1

Chemical change because gas formation was observed, which indicated that the calcium carbonate was transformed into a different substance.

The formation of gas means that calcium carbonate has lost its chemical identity and converted to something else with a different set of atoms arranged in a different manner.

Answer 2

Answer: Option (c) is the correct answer.

Explanation:

When calcium corbonate and hydrochloric acid react then the reaction will be as follows.

 $CaCO_{3}(s) + HCl(l) \rightarrow CaCl_{2} (aq)+ CO_{2} (g) + H_{2}O(l)$

This reaction shows a chemical change as the calcium carbonate has transformed into calcium chloride, that is, the chemical composition of calcium carbonate has changed accompanied by the formation of carbon dioxide gas and water.

Thus, we can conclude that this reaction represents a chemical change because gas formation was observed, which indicated that the calcium carbonate was transformed into a different substance.