Problem 59 - Chemistry

Question

Describe one industrial and one laboratory preparation of \(\mathrm{O}_{2}\).

Step-by-Step Solution

Answer

Oxygen gas (\(\mathrm{O}_{2}\)) is industrially prepared via the fractional distillation of liquified air. In a laboratory setting, it can be prepared by decomposing chemicals such as potassium chlorate (\(\mathrm{KClO_3}\)) under heat and a catalyst like MnO2, which produces \(\mathrm{O}_{2}\) gas and Potassium chloride.

Step 1: Industrial preparation of \(\mathrm{O}_{2}\)

Industrially, \(O_2\) or Oxygen is commonly prepared by the fractional distillation of liquefied air. Air is liquified by applying high pressure and lowering the temperature. In this liquified air, Oxygen gas is separated using fractional distillation. The liquified air is allowed to warm up slowly in a fractional distillation column where different components of air boil off and can be separated at their respective boiling points, and oxygen is collected at its boiling point.

Step 2: Laboratory preparation of \(O_2\)

Laboratory preparation of \(\mathrm{O}_{2}\) usually involves the decomposition of certain chemicals that produce \(\mathrm{O}_{2}\) as a by-product. One common method is the decomposition of potassium chlorate (\(\mathrm{KClO}_{3}\)) when heated in presence of MnO2 as a catalyst, where it decomposes to produce \(\mathrm{O}_{2}\) and Potassium chloride. The reaction can be outlined as follows: \[2\mathrm{KClO}_{3}\xrightarrow{\mathrm{MnO2}} 2\mathrm{KCl} + 3\mathrm{O}_{2}\]

Key Concepts

Industrial Preparation of Oxygen

Producing oxygen on an industrial scale is a fascinating process. The most common method involves the fractional distillation of liquefied air. First, air is cooled and compressed until it becomes a liquid. This is achieved by applying high pressure and low temperatures.
Once air is liquefied, it is warmed up in a fractional distillation column. Each component of air has a different boiling point, which allows them to separate as they evaporate. Oxygen, with a boiling point of -183°C, can be collected as it evaporates at this specific temperature. This method ensures that large quantities of oxygen are produced efficiently.

Fractional Distillation

Fractional distillation is a key technique used to separate components of a mixture based on their boiling points. It is extensively used in the industrial preparation of gases like oxygen and nitrogen from air.
In the process, liquefied air is introduced into a tall column. As the liquid warms, each gas evaporates at its respective boiling point, allowing for separation. More volatile gases boil off first, and the distillation tower captures each gas as it condenses.
This method is effective for producing high-purity oxygen, as it relies on differences in boiling points to separate gases cleanly.

Laboratory Preparation of Oxygen

In a laboratory setting, preparing oxygen is often straightforward and involves simple chemical reactions. A common method is through the decomposition of potassium chlorate (KClO_3).
When heated in the presence of a catalyst like manganese dioxide (MnO_2), potassium chlorate decomposes, releasing oxygen and forming potassium chloride. The reaction is as follows:
\[2\mathrm{KClO}_3 \xrightarrow{\mathrm{MnO_2}} 2\mathrm{KCl} + 3\mathrm{O}_2\]
This method is practical for small-scale preparation due to its simplicity and the easy availability of the chemicals involved.

Decomposition of Potassium Chlorate

The decomposition of potassium chlorate is a classic experiment in chemistry labs. By heating KClO_3, it breaks down into potassium chloride ( KCl) and oxygen gas ( O_2). The presence of a catalyst, such as manganese dioxide ( MnO_2), speeds up the reaction.
During this process, oxygen is generated efficiently, making it a favorite method for obtaining oxygen in schools and small laboratories. The reaction is exothermic, meaning it releases heat, which helps maintain the reaction cycle until the complete decomposition of potassium chlorate has occurred.