Green Chemistry and the Ten Commandments

T 1 ­­­­­­­­­­­­­­­­­­­­­­283 ̊

V 2 ­=­V 1 ­×­­

T 2

­­=­12.0­L­× 363 ̊­­=­15.4­L­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­(8.1.4)

As another example consider the effects of a change of pressure, holding both the
temperature and number of moles constant. Calculate the new volume of a quantity of
gas occupying initially 16.0 L at a pressure of 0.900 atm when the pressure is changed
to 1.20 atm. In this case, both n and T remain the same and cancel out of the equation
giving the following relationship:

P 2 ­­­­­­­­­­­­­­­­­­­­­­­1.20­atm

V 2 ­=­V 1 ­×­­P^1 ­­=­16.0­L­× ­0.900­atm­­=­12.0­L­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­(8.1.5)

Note that an increase in temperature increases the volume and an increase in pressure
decreases the volume. These effects are readily visualized because higher temperatures
mean more vigorous movement of gas molecules, tending to expand the gas, and
increasing pressure is manifested by “squeezing” the gas into a smaller volume.

The Protective Atmosphere

The atmosphere is the air around and above us. We know we must have air to
breathe. A human deprived of air’s life-giving oxygen for just a brief time will lose
consciousness, and within a few minutes will die. But air is far more than just a source
of oxygen. That is because it protects Earth’s organisms in ways that are absolutely
essential for their existence. One major protective function is to act as a blanket to keep
us warm. It does that by reabsorbing the infrared radiation by which Earth radiates the
energy that it receives from the sun. By delaying the exit of this energy into outer space,
the average temperature of Earth’s surface remains at about 15 ̊C at sea level, though
much colder at certain times and places and significantly warmer at others. Without this
warming effect, plants could not grow and most other known organisms could not exist.
The second protective function of the atmosphere is absorption of very short wavelength
ultraviolet solar radiation. Were this radiation to reach our level, it would tear apart
biomolecules, especially DNA involved in cell regulation and reproduction, making it
impossible for most life forms to exist.
What is air? At our level, it is a mixture of gases of uniform composition, except
for water vapor, which composes 1-3% of the atmosphere by volume, and some of the
trace gases, such as pollutant sulfur dioxide. On a dry basis, air is 78.1% (by volume)
nitrogen, 21.0% oxygen, 0.9% argon, and 0.04% carbon dioxide. Normally, air is 1–3%
water vapor by volume. Trace gases at levels below 0.002% in air include ammonia,
carbon monoxide, helium, hydrogen, krypton, methane, neon, nitrogen dioxide, nitrous
oxide, ozone, sulfur dioxide, and xenon.
Although one might get the impression that the atmosphere is very thick, it is “tissue
thin” compared to Earth’s diameter. Consider a corporate jet aircraft cruising at 35,000
feet (about 6.6 miles or 10.7 kilometers). In the unlikely event of sudden, catastrophic
loss of pressure in the pressurized cockpit, the pilot has only about 15 seconds to grab an
oxygen mask before losing consciousness (the passengers in the cabin have an equally

Chap. 8. Air and the Atmosphere 197