Question

What are the standard temperature (in kelvin) and pressure (in atm) conditions for gas measurements?

Answer 1

STP is the abbreviation for Standard Temperature and Pressure. STP most commonly is used when performing calculations on gases, such as gas density. The standard temperature is $273K$ and the standard pressure is $1$ atm pressure.

Complete Step By Step Answer:
Standard temperature and pressure are standard sets of conditions for experimental measurements to be established to allow comparisons to be made between different sets of data. The most used standards are those of the IUPAC and the NIST, although these are not universally accepted standards. Other organizations have established a variety of alternative definitions for their standard reference conditions. NIST uses a temperature of ${20^ \circ }C$ ( $293.15K,{68^ \circ }F$ ) and an absolute pressure of $1$ atm. This standard is also called normal temperature and pressure.
STP is $273.15K$and $0.98692atm$ .
STP is defined as $273.15K$ and a pressure of exactly $100$ kPa ( $1$ bar).
$\Rightarrow 1$ atm $= 101.325$ kPa, so
$\Rightarrow 100$ kPa $\times \dfrac{{1atm}}{{101.325kPa}}$ $= 0.98692$ atm.

Additional Information:
STP is used in many thermodynamic calculations and tabulations. Certain properties of matter such as density, viscosity, boiling point etc. will vary with changes in temperature or pressure. Having one common set of conditions for tabulating these values makes comparisons possible and eases calculations.

Note:
Standard temperature is defined as zero degrees Celsius, which translates to $32$ degrees Fahrenheit $273.15$ degrees kelvin. This is essentially the freezing point of pure water at sea level, in air at standard pressure. Standard pressure supports $760$ millimeters in a mercurial barometer. This is about $29.9$ inches of mercury, and represents approximately $14.7$ pounds per inch. The air in such a column would weigh about $14.7$ pounds.