What is the molecular formula for chalk?

The correct answer is CaCO3.

Key Points

• Chalk is primarily composed of calcium carbonate (CaCO3), a naturally occurring compound.
• Calcium carbonate is a white, insoluble solid found in sedimentary rocks such as limestone and chalk.
• It is formed mainly by the accumulation of marine organism shells, particularly those of plankton, over millions of years.
• Chalk is widely used in various industries, including construction (as a component of cement), agriculture (to neutralize acidic soil), and in classrooms (as blackboard chalk, although modern chalk is often synthetic).
• The molecular formula CaCO3 represents one calcium atom, one carbon atom, and three oxygen atoms.

Additional Information

• Calcium Carbonate Usage:
  • It is used in the production of lime (CaO) and cement.
  • In the pharmaceutical industry, it acts as a calcium supplement and an antacid.
  • In the food industry, it is used as an additive (E170) for acidity regulation.
• Properties of Calcium Carbonate:
  • It has a molar mass of approximately 100.09 g/mol.
  • It is relatively insoluble in water but reacts with acids, releasing carbon dioxide.
  • Its crystalline forms include calcite and aragonite.
• Formation of Chalk:
  • Chalk is formed from the microscopic remains of planktonic organisms such as coccolithophores.
  • The accumulation of these remains over geological time leads to the formation of chalk beds.
• Other Forms of Calcium Carbonate:
  • Marble is a metamorphic form of calcium carbonate.
  • Limestone is a sedimentary form, widely used in construction.
• Environmental Importance:
  • Calcium carbonate plays a role in carbon cycling by trapping carbon dioxide in rock formations.
  • It is also used to combat ocean acidification by neutralizing excess acidity in seawater.