A Level Chemistry OCR Practice Exam

What is the significance of the number 6.02 × 10^23?

1. The number of grams in a mole of any substance

2. Avogadro's number, representing the quantity of atoms in a mole

3. The speed of light in a vacuum

4. The number of molecules in a liter of water

The correct answer is: Avogadro's number, representing the quantity of atoms in a mole

The number 6.02 × 10^23 is significant because it is known as Avogadro's number. This constant represents the quantity of atoms, molecules, or particles present in one mole of a substance, which provides a bridge between the atomic scale and the macroscopic scale of materials. Understanding that one mole of any substance contains this fixed number of entities helps chemists perform calculations related to reaction stoichiometry and the behavior of gases, liquids, and solids at the molecular level. This number is fundamental in chemistry as it allows for the conversion between the amount of substance measured in grams and the number of atoms or molecules, facilitating quantitative analysis in various chemical reactions. The other options do not pertain directly to the significance of 6.02 × 10^23. While the mass of a mole of a substance is related to its molar mass, it is not defined by this specific number. The speed of light in a vacuum and the number of molecules in a liter of water are entirely different concepts and values, thus illustrating the unique role that Avogadro's number plays in the field of chemistry.