A student added a piece of limestone to a solution of hydrochloric acid. Based on observations, the student infers that a chemic
al 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
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.
