Question

What was the observation made by Joseph Priestley during the experiment done for discovery of oxygen?
A. A colored gas is collected in the jar
B. A colorless gas is collected in the jar
C. No gas collected in the jar
D. None of the above

Answer 1

Oxygen is a chemical element having atomic number 8 and has the symbol $O$. Oxygen was discovered in the year 1772 by heating potassium nitrate, mercuric oxide and many other substances.

Complete step by step answer:
Oxygen was discovered by the Swedish chemist, Carl William Scheele in the year 1772, by heating potassium nitrate, mercuric oxide and many other substances. In the year 1774, an English chemist, Joseph Priestley independently discovered oxygen by the thermal decomposition of mercuric oxide and published the finding in the same year.
Joseph experimented using his burning lens to heat up a sample of mercuric oxides after that he observed a remarkable gas was emitted from this process. He collects the colorless gas in a jar. After that he also conducted a number of experiments to understand the importance of air for the survival of the living organisms.

Hence, the correct answer is option (b) i.e. the observation made by Joseph Priestley during the experiment done for discovery of oxygen is a colorless gas is collected in the jar.

Note: Oxygen has two allotropic forms i.e. diatomic and triatomic. The properties of diatomic form suggest that six electron bonds the atom and the two electrons remain unpaired leading to the paramagnetic behavior of oxygen. This experiment paved the ways of understanding and categorizing various such gases and Joseph Priestly although with an accidental beginning, discovered oxygen.