Question

A student added a piece of limestone to a solution of hydrochloric acid. Based on observations, the student infers that a chemical reaction took place. Which of the following is an observation that directly supports the inference?
O A. Bubbles formed.
OB. The limestone dissolved.
O C. The solution became doudy.
OD. The volume of the solution increased​

Answer 1

Answer:

A. Bubbles formed

Explanation:

When a student added a piece of limestone to a solution of hydrochloric acid, bubbles are formed.

The bubbles are as a result of the CO2 gas that is formed.

Below is the reaction:

CaCO3+2HCl → CO2+H2O + Ca++ + 2Cl-

From the left hand side, we can see that the reaction is with limestone and hydrochloric acid. Their reaction forms carbon dioxide gas (CO2), water (H2O), dissolved calcium (Ca++) and dissolved chlorine (Cl-) on the right hand side.

With due observation, bubbles will be seen evolving from the reaction. These bubbles formed is the carbon dioxide gas which reveals that a reaction is taking place.