Ideal Gas Law
Definition and meaning of Ideal Gas Law in chemistry.
Ideal gas law is the equation of state PV = nRT, which relates the pressure, volume, amount, and absolute temperature of an ideal gas.
In more detail
The law combines Boyle's law (P inversely proportional to V), Charles's law (V proportional to T), and Avogadro's law (V proportional to n) into a single equation using the gas constant R. It models a hypothetical "ideal gas" whose molecules occupy negligible volume and exert no intermolecular forces on each other. Real gases approximate this behavior well at low pressure and high temperature, but deviate at high pressure or low temperature, where molecular volume and intermolecular attractions become significant (better described by the van der Waals equation).
Key facts
| Equation | PV = nRT |
|---|---|
| Gas constant (R) | 8.314 J/(mol·K) or 0.08206 L·atm/(mol·K) |
| Key assumptions | No intermolecular forces; negligible molecular volume |
| Field | Physical Chemistry |
Find the volume occupied by 1.00 mol of an ideal gas at standard temperature and pressure (273.15 K, 1 atm): V = nRT/P = (1.00 mol)(0.08206 L·atm/mol·K)(273.15 K)/(1 atm) = 22.4 L.
Frequently asked questions
What does each symbol in PV = nRT stand for?
P is pressure, V is volume, n is the number of moles of gas, R is the universal gas constant, and T is absolute temperature in kelvins.
When does the ideal gas law fail to describe real gases accurately?
It becomes inaccurate at high pressure and low temperature, where intermolecular attractions and the finite volume of gas molecules matter; the van der Waals equation corrects for these effects.