Is Calcium Carbonate Acidic or Basic?


Calcium carbonate is a chemical compound with the formula CaCO3. It is commonly found in rocks, shells, and minerals such as limestone, marble, and chalk. One of the key aspects of understanding calcium carbonate is determining whether it is acidic or basic. In this article, we will explore the properties of calcium carbonate and delve into its acid-base behavior.

The Nature of Calcium Carbonate

Calcium carbonate is an inorganic compound that exists in various forms, including powder, granules, and solid crystals. It is a white, odorless substance that is insoluble in water. The compound is composed of calcium ions (Ca2+) and carbonate ions (CO32-).

Chemical Structure

The chemical structure of calcium carbonate consists of one calcium cation bonded to one carbonate anion. The carbonate ion is a polyatomic ion with the formula CO32-, comprising one carbon atom bonded to three oxygen atoms.

Chemical Structure:

Compound Chemical Formula
Calcium Carbonate CaCO3
Carbonate Ion CO32-

Physical Properties

Calcium carbonate exhibits several physical properties that make it a versatile compound:

  • Solubility: Calcium carbonate has low solubility in water, with approximately 0.0013 grams dissolving in one liter of water at room temperature.
  • Melting Point: The compound decomposes upon heating, starting to lose carbon dioxide (CO2) at around 550°C (1,022°F).
  • Crystal Structure: It crystallizes in the trigonal crystal system, forming rhombohedral or hexagonal crystals.
  • Hardness: Calcium carbonate has a Mohs hardness of 3, which means it is relatively soft.

Acid-Base Behavior of Calcium Carbonate

To determine whether calcium carbonate is acidic or basic, we need to understand its reaction with acids and bases. The acid-base behavior of calcium carbonate can be explained by its ability to act as both an acid and a base.

Reaction with Acids

When calcium carbonate reacts with acids, it undergoes a neutralization reaction, forming a salt and releasing carbon dioxide gas. This reaction can be represented by the following equation:

CaCO3 + 2HCl → CaCl2 + H2O + CO2

In this reaction, calcium carbonate (CaCO3) reacts with hydrochloric acid (HCl) to produce calcium chloride (CaCl2), water (H2O), and carbon dioxide (CO2) gas.

Reaction with Bases

Calcium carbonate can also react with bases, undergoing a similar neutralization reaction. For example, when calcium carbonate reacts with sodium hydroxide (NaOH), the following reaction occurs:

CaCO3 + 2NaOH → Ca(OH)2 + Na2CO3

In this reaction, calcium carbonate (CaCO3) reacts with sodium hydroxide (NaOH) to form calcium hydroxide (Ca(OH)2) and sodium carbonate (Na2CO3).

Factors Influencing Acid-Base Behavior

The acid-base behavior of calcium carbonate can be influenced by several factors, including concentration, temperature, and pressure.


The concentration of calcium carbonate in a solution can affect its acid-base behavior. Higher concentrations of calcium carbonate may exhibit stronger acidic or basic properties compared to lower concentrations.


Temperature can also impact the acid-base behavior of calcium carbonate. Generally, increasing the temperature of a reaction can enhance the reactivity of the compound, resulting in a stronger acid or base behavior.


Pressure, particularly in the case of gaseous carbon dioxide, can affect the acid-base behavior of calcium carbonate. Higher pressure can increase the solubility of carbon dioxide and subsequently influence the equilibrium of the acid-base reaction.

Frequently Asked Questions (FAQs)

Q1: What are the common uses of calcium carbonate?

A1: Calcium carbonate has numerous applications across various industries. It is widely used in construction as a building material, in agriculture as a soil conditioner, in the manufacturing of paper, paints, and plastics, and as a dietary supplement for calcium intake.

Q2: Is calcium carbonate safe for consumption?

A2: Calcium carbonate is generally considered safe for consumption. However, excessive intake may lead to side effects such as constipation, bloating, and gas. It is important to follow recommended dosage guidelines and consult a healthcare professional if necessary.

Q3: Can calcium carbonate be used as an antacid?

A3: Yes, calcium carbonate is commonly used as an antacid to neutralize excess stomach acid and provide relief from heartburn, indigestion, and acid reflux. It reacts with stomach acid to form calcium chloride, water, and carbon dioxide.

Q4: Does calcium carbonate affect water hardness?

A4: Yes, calcium carbonate is a major contributor to water hardness. It can precipitate out of water, forming scale deposits in pipes and appliances. Water hardness can be reduced through various methods, such as water softening treatments or the use of chelating agents.

Q5: Can calcium carbonate be used in toothpaste?

A5: Yes, calcium carbonate is commonly used in toothpaste formulations as an abrasive agent. It helps remove plaque and surface stains from teeth, contributing to oral hygiene.

A6: Calcium carbonate is considered environmentally safe and non-toxic. However, excessive release of calcium carbonate into aquatic environments can lead to increased water hardness and potential ecological impacts on aquatic organisms.


Calcium carbonate exhibits both acidic and basic properties, making it amphoteric in nature. It reacts with acids to form salts and carbon dioxide gas, while reacting with bases to form salts and water. The acid-base behavior of calcium carbonate can be influenced by factors such as concentration, temperature, and pressure. Understanding the acid-base properties of calcium carbonate is crucial in various applications, ranging from construction to medicine.

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