Standard Conditions (STP)
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Definition
The IUPAC reference state for gas measurements: 0°C (273.15 K) and 101.325 kPa (1 atm), at which one mole of an ideal gas occupies 22.414 liters.
Explanation
Standard conditions allow meaningful comparison of gas volumes and reaction rates across laboratories. One mole of oxygen at STP occupies 22.414 L; at room temperature (25°C, 100 kPa) — the newer IUPAC standard conditions — it occupies 24.789 L, about 10.6% more. Always check which standard a source uses, since older chemistry texts use 0°C while newer ones use 25°C.
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