Describe the industrial production of oxygen and the concentration of nitric acid.

a) Oxygen is obtained from air on a large scale through the fractional distillation of liquid air.

• Air is first filtered to remove dust particles.
• It is then compressed and cooled to remove carbon dioxide and water vapor.
• The remaining air is further cooled to a very low temperature (around $-200^\circ C$) until it liquefies.
• The liquid air is then fed into a fractionating column, where it is slowly warmed.
• Nitrogen (boiling point $-196^\circ C$) distills off first, followed by argon (boiling point $-186^\circ C$).
• Liquid oxygen (boiling point $-183^\circ C$) is left behind at the bottom of the column.

b) To increase the concentration of nitric acid from 60% to about 98%:

• The 60% nitric acid is mixed with concentrated sulfuric acid.
• The mixture is then distilled. Concentrated sulfuric acid acts as a dehydrating agent, absorbing water from the nitric acid.
• This allows the more concentrated nitric acid (up to 98%) to be distilled off.