Which experiment did Antoine Lavoisier use to challenge the phlogiston theory?

• A. He used cathode ray tubes to discover electrons.
• B. He measured the mass of substances before and after combustion to demonstrate conservation of mass.
• C. He heated mercury oxide and observed the release of phlogiston.
• D. He bombarded gold foil with alpha particles to study atomic structure.

Answer: (B)

Verified step by step guidance

1. Understand the historical context: The phlogiston theory was an early scientific hypothesis that attempted to explain combustion by proposing a substance called 'phlogiston' was released during burning.
2. Identify Lavoisier's key contribution: Antoine Lavoisier challenged this theory by carefully measuring the mass of substances before and after combustion reactions.
3. Focus on the experiment: Lavoisier heated substances like mercury oxide and measured the mass of the reactants and products, showing that mass was conserved and that combustion involved oxygen from the air, not the release of phlogiston.
4. Recognize the significance: This experiment demonstrated the Law of Conservation of Mass, disproving the phlogiston theory and laying the foundation for modern chemistry.
5. Note what Lavoisier did not do: He did not use cathode ray tubes, nor did he bombard gold foil with alpha particles; those experiments were conducted by later scientists.