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STP Chemistry Flashcards
Free Cards on Standard Temperature and Pressure
These free Chemistry flashcards focus on standard temperature and pressure, molar volumes and gas law calculations. Useful for A Level Chemistry and university level study.
Question
What does STP stand for?
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Answer
Standard Temperature and Pressure — a set of standard conditions used in chemistry to allow fair comparisons between experimental measurements.
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Question
What is the current IUPAC definition of STP (since 1982)?
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Answer
A temperature of 273.15 K (0 °C) and an absolute pressure of exactly 1 bar (100,000 Pa).
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Question
What was the original IUPAC definition of STP before 1982?
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Answer
A temperature of 273.15 K (0 °C) and an absolute pressure of exactly 1 atm (101.325 kPa).
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Question
Why did IUPAC change the definition of STP in 1982?
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Answer
It switched from 1 atm to 1 bar to align with the metric system — the Pascal (bar) is a metric unit, whereas the atmosphere is not.
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Question
What is SATP and how does it differ from STP?
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Answer
Standard Ambient Temperature and Pressure — defined by IUPAC as 298.15 K (25 °C) and 1 atm (101.325 kPa). It uses a higher, more "room-like" temperature than STP.
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Question
What conditions does NIST use as its standard (NTP)?
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Answer
Normal Temperature and Pressure (NTP): 20 °C (293.15 K) and 1 atm (101.325 kPa).
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Question
What is the molar volume of an ideal gas at STP (IUPAC, since 1982)?
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Answer
22.711 dm³/mol — calculated using the ideal gas law at 0 °C and 100 kPa.
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Question
What is the molar volume of an ideal gas at the old STP (0 °C, 101.325 kPa)?
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Answer
22.414 dm³/mol — this is the value still commonly quoted in many textbooks.
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Question
What is the molar volume of an ideal gas at SATP (25 °C, 100 kPa)?
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Answer
24.790 dm³/mol.
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Question
What is the ideal gas law formula used to calculate molar volume?
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Answer
Vm = RT/P, where R = 8.3145 J/(mol·K), T is temperature in Kelvin, and P is pressure in Pascals.
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