Description : Which one out of the following helps in burning? (1) Oxygen (2) Carbon monoxide (3) Nitrogen (4) Carbon dioxide
Last Answer : (1) Oxygen Explanation: Karl Scheele, the Swedish chemist, was the first to prepare oxygen by heating mercuric oxide in 1772. Joseph Priestley, the English chemist, also prepared oxygen in 1774 ... on mercuric oxide. Its elemental nature was, however, established by the French chemist, Lavoisier.