Gas Laws
Experiment #1 -- Boyle's Law (Robert Boyle 1627-1691)
| Purpose: | To determine the relationship between gas pressure and gas volume. |
| Constants: | amount of gas gas temperature |
| Data & Analysis | P → gas
pressure V → gas volume P µ (1 / V) P µ V-1 P = k1 V-1 |
| Conclusions: | Gas pressure is inversely proportional to gas volume |
Experiment #2 -- Charles' Law (Jacques Charles 1747-1823)
| Purpose: | To determine the relationship between gas volume and gas temperature. |
| Constants: | amount of gas gas pressure |
| Data & Analysis | V → gas
volume T → gas temperature V µ T V = k2 T |
| Conclusions: | Gas volume is directly proportional to gas temperature |
Ideal Gas Law
Using Boyle's Law and Charles' Law the ideal gas law is the relationship between gas pressure, gas volume and gas temperature.
| Boyles Law | Charles' Law |
| P = k1 V-1 | V = k2 T |
| P V = k1 | V / T = k2 |
| P V / T = k3 | |
| P V / T = N kB | |
The constant k3 turns out to be related to the quantity in our experiments that was held constant - The Amount of Gas.
N is the number of molecules of gas & kB (Boltzmann's Constant) = 1.38 x 10-23 J / K
But it is a little impractical to measure the amount of gas in terms of number of molecules of gas. (One teaspoon of air in this room contains an immense number of molecules.) Typically we measure amounts of gas in terms of moles. Remember that 6.022 x 1023 molecules of gas = 1 mole of gas. The ideal gas law can then be rewritten as
|
P V / T = n R |
n is the number of moles of gas & R = 8.31 J / (mol K)
You may be more used to seeing the ideal gas law written as
|
P V = n R T |
Experiment #3 --
| Purpose: | To determine the relationship between gas pressure and gas temperature. |
| Constants: | amount of gas gas volume |
| Data & Analysis | P →
gas pressure T → gas temperature P µ T P = k4 T k4 = n R / V |
| Conclusions: | Gas pressure is directly proportional to gas temperature. |