Solve PV = nRT for any variable with flexible units.
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The ideal gas law PV = nRT relates pressure (P), volume (V), amount of gas in moles (n), and temperature (T) through the universal gas constant R = 0.08206 L·atm/(mol·K).
Worked example: What volume does 2.5 mol of an ideal gas occupy at 25°C and 1 atm? T = 25 + 273.15 = 298.15 K. V = nRT/P = (2.5)(0.08206)(298.15)/(1) = 61.2 L.
The ideal gas law assumes gas molecules have negligible volume and no intermolecular attractions. It works well for most gases at moderate temperatures and pressures, but breaks down at very high pressures or very low temperatures where real gas behavior (van der Waals forces, molecular volume) becomes significant.
At STP (0°C, 1 atm), one mole of an ideal gas occupies 22.414 L. At standard lab conditions (25°C, 1 atm), it occupies 24.47 L.