Is an ideal gas always measured using STP conditions?

Simply, the answer is yes.

• An ideal gas is a theoretical gas, so ideal gases are hypothetical.

• At high temperatures, real gases move faster. So, there is no need for intermolecular attractions. At low pressure, a gas sample occupies high volume, so volume of one molecule is negligible.

• Real gases deviate to ideal behaviors at high temperature and at low pressure, and real gases deviate from ideal behaviors at low temperature and at high pressure, these pictures may help you get clear idea.

The ##1^(st)## graph shows that at low pressure real gases are closer to ideal gas behaviors, The ##2^(nd)## graph shows at high temperature real gases are closer to ideal* behavior.

##STP## conditions ====> The temperature is 0°C or 273 K . The pressure is =======>1 atmosphere or 760 mmHg volume (molar volume)==> 22.4 L

Factors needed to express behaviour of gas :

1. Pressure ##(P)##
2. Volume ##(V)##
3. Amount of gas ##(n)##
4. Temperature ##(T)##

You might know this equation,

##PV##=##ZnRT##

##Z##===> Compressibility factor ##R##===.>Universal gas constant.

To know more about derrivation of ideal gas equation visit http://chemblogc.blogspot.com/2014/04/gaseous-state-of-matter.html

For ideal gases ##Z##=1, so ideal gas equation is ##PV##=##nRT##. So here is how universal gas constant ##R## is calculated. In this point ##STP## conditions are important

##R##=##P####V##/##n####T## ##P##==>Standard temperature= 0°C or 273 K ##V##==>Standard volume = 22.4 L Here ##n## is equal to one mole of gas so, ##R##===>Universal gas constant= ##8.314## ##j## ##mol^-## ##k^-## So this ##R## is used as universal gas constant for any calculation regarding the ideal gas equation ##PV##=##nRT##.

I hope it is clear why ##STP## conditions are important.

Standard conditions for temperature and pressure are standard sets of conditions for experimental measurements.

So, ideal gases are always measured using STP conditions.