CHAPTER 2. ATMOSPHERIC PRESSURE
The gas laws were developed at the end of the 18th century, when scientists began to realize that relationships between pressure, volume and temperature of a sample of gas As a mathematical equation, Charles's law is written as either: . mixture in the atmosphere: and PH2O is the water pressure at that temperature. The pressure on the gas is atmospheric pressure plus the difference in the sides by P gives an equation illustrating the inverse relationship between P and V. 1. 2. Summary of Constants. 1. 3. Summary of Equations. 2. 4. Augmented Table 4. 2. 5. Calculating Temperature and Pressure. 3. 6. C++ Implementation. 3.
This equation states that the product of the initial volume and pressure is equal to the product of the volume and pressure after a change in one of them under constant temperature.
Barometric formula - Wikipedia
For example, if the initial volume was mL at a pressure of torr, when the volume is compressed to mL, what is the pressure? Plug in the values: The Temperature-Volume Law This law states that the volume of a given amount of gas held at constant pressure is directly proportional to the Kelvin temperature. V Same as before, a constant can be put in: Also same as before, initial and final volumes and temperatures under constant pressure can be calculated.
The Pressure Temperature Law This law states that the pressure of a given amount of gas held at constant volume is directly proportional to the Kelvin temperature.
P Same as before, a constant can be put in: The Volume Amount Law Amedeo Avogadro Gives the relationship between volume and amount when pressure and temperature are held constant.
The Barometric Formula
Remember amount is measured in moles. Also, since volume is one of the variables, that means the container holding the gas is flexible in some way and can expand or contract.
If the amount of gas in a container is increased, the volume increases. If the amount of gas in a container is decreased, the volume decreases. V As before, a constant can be put in: The Combined Gas Law Now we can combine everything we have into one proportion: The volume of a given amount of gas is proportional to the ratio of its Kelvin temperature and its pressure.
Same as before, a constant can be put in: The Ideal Gas Law The previous laws all assume that the gas being measured is an ideal gas, a gas that obeys them all exactly. But over a wide range of temperature, pressure, and volume, real gases deviate slightly from ideal.
Since, according to Avogadro, the same volumes of gas contain the same number of moles, chemists could now determine the formulas of gaseous elements and their formula masses. Dalton's law stipulates that each component of the air mixture must behave as if it were alone in the atmosphere.
One might then expect different components to have different scale heights determined by their molecular weight.
In particular, considering the difference in molecular weight between N2 and O2, one might expect the O2 mixing ratio to decrease with altitude.
However, gravitational separation of the air mixture takes place by molecular diffusion, which is considerably slower than turbulent vertical mixing of air for altitudes below km problem 4.
Turbulent mixing thus maintains a homogeneous lower atmosphere. Only above km does significant gravitational separation of gases begin to take place, with lighter gases being enriched at higher altitudes. During the debate over the harmful effects of chlorofluorocarbons CFCs on stratospheric ozone, some not-so-reputable scientists claimed that CFCs could not possibly reach the stratosphere because of their high molecular weights and hence low scale heights.
In reality, turbulent mixing of air ensures that CFC mixing ratios in air entering the stratosphere are essentially the same as those in surface air.
Relationships among Pressure, Temperature, Volume, and Amount
Exercise The cruising altitudes of subsonic and supersonic aircraft are 12 km and 20 km respectively. What is the relative difference in air density between these two altitudes? The air density at 20 km is only a third of that at 12 km.