8. Describe the experience Lavoisier performed to disprove the existence of phlo

Question

8. Describe the experience Lavoisier performed to disprove the existence of phlogiston and officially discover oxygen How many elements did Lavoisier identify in his original list? What were the 4 categories? 9. What ultimately happened to Lavoisier during the French Revolution? a. 10. What element did Humphrey Davey isolate by passing a current through molten potash? pisode 2: The Order of the Elements 11. What characteristic of atoms did Dalton use to try and organize the known 55 elements? 12. Since we cannot use regular light to view atoms, what kind of microscope must we use? Why can't we use regular light? 13. In the process of making his own glassware he needed to conduct his experiments, what element did Berzelius discover? 14. What is a triad? 5. What did Cannizzaro use/measure to determine the atomic mass of the elements? . What method did Mendeleev use to determine his arrangement of the periodic table?

Explanation / Answer

9.Concept of Phlogiston was introduced by German scientist Georg Ernst Stahl early in the 18 th century. He thought that a fire liked element called phlogiston is present in every combustible substances and released in times of combustion.

Lavoisier's in his experiment with phosphorus and sulfur (in which both of them burned readily) showed that both of the elements when burned in air gained weight. With lead calx ( now oxide) he showed that large mass of air was used in combustion . These results was not explained by phlogiston.

But that time Lavoisier realised that combustion requires air . The exact composition of air was not understood. In 1774 Priestley discovered a gas which help to burn candle. He named it pure air. Lavoisier repeated the experiment of Priestley. He explained from the experiment ( heating mercury calx) that air contain two type gas, one help to burn and respiration but another helps neither combustion nor respiration.

In 1777 Lavoisier proposed that the metal or organic compounds reacts with the part of air which help respiration. After 2 years he also proposed that the gas which supports respiration present in almost all acids.

That is why Lavoisier named it Oxygen from Greek words oxy ( means acid) and gen ( means generator) . Lavoisier further claimed that Stahl's concept of phlogiston is a myth . Then he proposed the theory on combustion in which oxygen plays key role. That is how the concept of phlogiston was disapproved.

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