A student is given two mineral samples that appear very similar. They both are opaque, white, and shiny. He knows that they are either calcite or quartz. To determine the identity of each mineral, the student puts a couple of drops of hydrochloric acid (HCl) on each sample. When calcite reacts with hydrochloric acid, carbon dioxide gas is produced. When HCl is placed on quartz, no changes are observed. Based on the information above, what evidence indicates that a chemical reaction occurs when HCl is placed on calcite?

Carbon dioxide is a new product formed from the reaction between calcite and HCl

Explanation:

Calcite is a mineral with the chemical formula CaCO₃. Hydrochloric acid reacts with calcite to liberate carbon dioxide and form calcium chloride and water. The equation of the reaction is given below:

CaCO₃ + HCl > CaCl₂ + H₂O + CO₂

In a chemical reaction or change, new products are formed which are different from the original elements or compounds reacting.

Since the carbon dioxide gas, calcium chloride and water are entirely new products formed from calcite and hydrochloric acid, the reaction between calcite and HCl is a chemical reaction.

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