Ideal Gas Law
Pressure, temperature, volume relationships
The Ideal Gas Law
PV = nRT relates pressure (P), volume (V), temperature (T), and moles (n). R = 8.314 J/(mol.K). Temperature must be in kelvin: K = degrees C + 273. Combines Boyle's law, Charles's law, and Avogadro's law.
Example
Worked Example
Calculate the volume of 2 mol gas at 25 C and 101 325 Pa. T = 25 + 273 = 298 K. V = nRT/P = (2)(8.314)(298)/101 325 = 0.0489 m cubed = 48.9 dm cubed. At STP, 1 mol of any gas occupies 22.4 dm cubed.
Note
Exam Tip
Always convert temperature to kelvin. Check unit consistency: pressure in Pa, volume in m cubed, R = 8.314 J/(mol.K).
Key Vocabulary
Ideal gasA hypothetical gas whose particles have no volume and no intermolecular forces
MoleThe SI unit for amount of substance, equal to 6.022 x 10 to the 23 particles
STPStandard Temperature and Pressure: 0 C (273 K) and 101 325 Pa
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Ideal gas
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