Which method for preparing oxygen achieves 99% purity?

Fractional distillation is the method for preparing oxygen that can achieve 99% purity. This process involves cooling air to extremely low temperatures until it liquefies. Once in liquid form, different components can be separated based on their boiling points. Oxygen has a lower boiling point than nitrogen, allowing it to be separated effectively when the mixture is gradually warmed.

This method is particularly efficient for oxygen production because it can target and separate oxygen from other gases present in the air, resulting in high-purity oxygen gas that is essential for medical and industrial use. By using repeated distillation, purity levels can reach near 99%, making it the preferred method for applications requiring high-quality oxygen. In contrast, other methods like physical separation and molecular sieve may not achieve the same levels of purity, as they typically target specific gas components based on different principles rather than relying on the precise boiling point separation achieved through fractional distillation.