What is the molar volume of gas at S.T.P. and S.A.T.P.?

[tasnim rahman]

What is the molar volume of gas at S.T.P. (standard temperature and pressure) and S.A.T.P.(standard ambient temperature and pressure)? I googled the one for S.T.P. and found it to be 24.414L for 1 atm standard pressure, but whereas in Wikipedia it is mentioned that IUPAC recommended the standard pressure to be 100kPa at S.T.P., most websites refer to 1 atm as the standard pressure. The one for S.A.T.P. is more elusive and different websites give different conditions and molar gas volumes. Any help, or reference to threads, websites, etc, is welcome.

 

[jbriggs444]

Why not solve PV=nRT for V, using the value of 8.3144621(75) for R and your chosen temperature and pressure.

For 1 mole at a pressure of 100kPa and a temperature of 273.15 Kelvins I get...

V = nRT/P = 1 * 8.314462175 * 273.15 / 100,000 = .02271095 cubic meters = 22.7 liters.

Mind you, I'm just an idiot using Google and what I learned in chemistry class a few decades ago.

 

[tasnim rahman]

Thanks, but I know how to calculate from the ideal gas equation. What I don't know is what are the exact conditions for S.T.P. and S.A.T.P.? Anyone any ideas?

 

[nasu]

The attribute "exact" is meaningless here. These are standards, so they are conventional, arbitrary. If there are several standards, as you found out, none is more (or less) exact than another.
Just use the one that applies in your field of activity.

 

[pmacias]

The molar volume of a gas at S.T.P. (standard temperature and pressure) is defined as 22.4 liters per mole at a temperature of 0°C and a pressure of 1 atmosphere. This value is based on the ideal gas law, which states that at S.T.P., 1 mole of any ideal gas will occupy a volume of 22.4 liters.

However, as you have mentioned, there is some confusion surrounding the definition of S.T.P. The International Union of Pure and Applied Chemistry (IUPAC) defines S.T.P. as a temperature of 0°C and a pressure of 100 kPa (kilopascals). This is equivalent to 1 bar or 0.9869 atm. So, if we use this definition, the molar volume of a gas at S.T.P. would be slightly different, at 22.711 liters per mole.

The reason for this discrepancy is that the definition of S.T.P. has changed over time. In the past, S.T.P. was defined as a temperature of 0°C and a pressure of 1 atmosphere (101.325 kPa). This is the definition that is still commonly used today.

As for S.A.T.P. (standard ambient temperature and pressure), there is not a universally agreed upon definition for this condition. Some sources define it as a temperature of 25°C and a pressure of 1 atmosphere, while others use a temperature of 20°C and a pressure of 1 atmosphere. This results in slightly different molar volumes for gases at S.A.T.P., ranging from 24.79 liters per mole to 24.92 liters per mole.

In conclusion, the molar volume of a gas at S.T.P. is 22.4 liters per mole based on the commonly used definition of 0°C and 1 atmosphere, but it can also be 22.711 liters per mole according to the IUPAC definition of 0°C and 100 kPa. The molar volume of a gas at S.A.T.P. varies depending on the definition used, but it is generally between 24.79 liters per mole and 24.92 liters per mole. It is important to be aware of these different definitions and values when working with gas laws and calculations.