Standard temperature and pressure (STP) is defined as

Explanation

STP is 273.15 K, which is 0 degrees Celsius, at a pressure of 1 atmosphere or 760 mm of mercury. One mole of any ideal gas occupies 22.4 dm3 under these conditions, which is the molar volume used throughout stoichiometry. The value of 25 degrees Celsius belongs to standard state conditions used in thermochemistry, a different convention.