The reaction between citric acid (H₃C₆H₅O₇) and calcium carbonate (CaCO₃) is a classic example of an acid-base reaction that produces carbon dioxide gas. Here's a breakdown:

The Reaction:

2 H₃C₆H₅O₇ (aq) + 3 CaCO₃ (s) → Ca₃(C₆H₅O₇)₂ (aq) + 3 CO₂ (g) + 3 H₂O (l)

Explanation:

* Citric acid (H₃C₆H₅O₇) acts as an acid, donating protons (H⁺) to the base.

* Calcium carbonate (CaCO₃) acts as a base, accepting the protons.

* Calcium citrate (Ca₃(C₆H₅O₇)₂) is formed, which is soluble in water.

* Carbon dioxide (CO₂) gas is released, causing effervescence.

* Water (H₂O) is also produced.

The overall reaction can be summarized as:

* Citric acid + Calcium carbonate → Calcium citrate + Carbon dioxide + Water

Observations:

* When citric acid is added to calcium carbonate, you'll observe fizzing due to the release of carbon dioxide gas.

* The mixture will become slightly warm as the reaction is exothermic.

* The solid calcium carbonate will gradually dissolve as it reacts with the citric acid.

Applications:

This reaction has various applications, including:

* Baking: Citric acid is used as a leavening agent in baking, reacting with baking soda (sodium bicarbonate) to produce carbon dioxide, which makes the dough rise.

* Cleaning: Citric acid is used in cleaning products to remove limescale, which is mainly calcium carbonate.

* Pharmaceuticals: Citric acid is used to make effervescent tablets and powders, where the reaction with calcium carbonate provides the fizz.

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