How does the percent of oxygen and nitrogen change with the increase in altitude?

Answer 1

When the altitude increases, the air becomes thinner. There are fewer air molecules at 60 km above the surface than 30 km. Thinner air has less air molecules because they are further apart. In dense air, the molecules are packed tighter.

Answer 2

Oxygen is produced by Plants and higher altitudes there are less plants so less oxygen.

Lack of oxygen causes high-altitude sickness. As altitude increases, the air becomes "thinner," which means less oxygen is in the atmosphere. You get less oxygen in your lungs with each breath, so the amount of oxygen in your blood declines. (This is called hypoxia) (hi-POKS'e-ah). All people can experience mountain sickness, but it may be more severe in people who have heart or lung problems.

Although the percentage of oxygen in inspired air is constant at different altitudes, the fall in atmospheric pressure at higher altitude decreases the partial pressure of inspired oxygen and hence the driving pressure for gas exchange in the lungs. An ocean of air is present up to 9-10 000 m, where the troposphere ends and the stratosphere begins. The weight of air above us is responsible for the atmospheric pressure, which is normally about 100 kPa at sea level. This atmospheric pressure is the sum of the partial pressures of the constituent gases, oxygen and nitrogen, and also the partial pressure of water vapour (6.3 kPa at 37°C). As oxygen is 21% of dry air, the inspired oxygen pressure is 0.21×(1006.3)=19.6 kPa at sea level.

Atmospheric pressure and inspired oxygen pressure fall roughly linearly with altitude to be 50% of the sea level value at 5500 m and only 30% of the sea level value at 8900 m (the height of the summit of Everest). A fall in inspired oxygen pressure reduces the driving pressure for gas exchange in the lungs and in turn produces a cascade of effects right down to the level of the mitochondria, the final destination of the oxygen.

Answer 3

The amount of Nitrogen increases and the amount of Oxygen decreases. This is why airplanes must pressurize before take-off.