In 1812, who described the hypothesis that equal volumes of different gases contain an equal number of molecules?  

The correct answer is Amedeo Avogadro.

Key Points

• Equal volumes of different gases containing an equal number of molecules were described by Avogadro. This concept is known as Avogadro's Law.
• Amedeo Avogadro was an Italian scientist whose work laid the foundation for molecular theory and stoichiometry in chemistry.
• Avogadro's Law is a key component of the Ideal Gas Law, which combines several gas laws (Boyle's, Charles's, and Avogadro's laws) into a single equation: PV = nRT.
• Avogadro's number, also known as Avogadro's constant, is defined as 6.022×10²³ (which can be atoms, molecules, or ions) per mole.

Additional Information

• James Watt
  • He improved the steam engine, making it more efficient and vital for the Industrial Revolution.
  • He introduced the concept of horsepower to measure engine power.
• John Dalton
  • He proposed the atomic theory, stating that all matter is composed of atoms, which are indivisible and unique to each element.
  • He established the law of multiple proportions, showing that elements combine in fixed ratios to form compounds.
• Albert Einstein
  • He explained the photoelectric effect, which contributed to the development of quantum mechanics and earned him the Nobel Prize in 1921.
  • He formulated the theory of relativity, with the equation E= MC² explaining the relationship between mass and energy.