Reference conditions for gases, commonly 0 degrees Celsius and 1 atm, where one mole occupies 22.4 L.
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Standard temperature and pressure are reference conditions used to compare gas volumes and amounts. Classic STP is 0°C and 1 atm, at which one mole of an ideal gas occupies 22.4 L. IUPAC now defines STP as 0°C and 1 bar, where the molar volume is 22.7 L. Standard ambient temperature and pressure, SATP, is 25°C and 1 bar, giving a molar volume of 24.8 L. Because the definitions differ, the conditions stated in a problem must always be checked before a molar volume is used.
Key ideas: Always write the reference conditions with the answer. Molar volumes: 22.414 L at 0 C and 1 atm, 22.711 L at 0 C and 1 bar, 24.79 L at 25 C and 1 bar. A quick check is V = nRT/P with the stated T and P. Gas densities at STP follow from molar mass divided by molar volume.
Common mistakes and connections: Using 22.4 L/mol for a gas at room temperature is the usual error, giving about 9 percent too little volume. It also applies only to gases, not liquids or solids. STP is not the same as standard state in thermodynamics, which uses 1 bar for any temperature. Related to molar volume and gas stoichiometry.
Reference conditions: STP is 273.15 K and 1 atm (1 bar in IUPAC), where one mole of ideal gas occupies about 22.4 L (22.7 L at 1 bar). The interactive lesson shows this as a live animation or chart.
At classic STP, 44 g of carbon dioxide (1 mol) occupies 22.4 L.
Reference conditions for gases, commonly 0 degrees Celsius and 1 atm, where one mole occupies 22.4 L.
Standard Temperature and Pressure is a beginner topic in States of Matter & Solutions. It needs no earlier chemistry lessons and is a good starting point.
Study these earlier topics in States of Matter & Solutions first: Bose-Einstein Condensate, Pressure, Barometer.
The next topics in States of Matter & Solutions are Boyle's Law and Charles's Law.
Yes. The interactive lesson includes a self-check question on Standard Temperature and Pressure, and the States of Matter & Solutions quiz draws on every topic in this area.
Standard Temperature and Pressure is topic 7 of 109 in States of Matter & Solutions.