[billnotgatez]

I just did a Google search on ideal gas calculator and here are a few of the returns.

http://www.chemicool.com/idealgas.html
http://www.hull.ac.uk/php/chsajb/general/ideal_gas.html
http://www.lmnoeng.com/idealgas.htm
http://library.thinkquest.org/2923/ideal.html
http://www.shodor.org/UNChem/advanced/gas/compress.html
http://www.nitrogenorder.org/cgi-bin/idealgas.cgi
http://www.extremescience.com/ideal-gas-law.htm
http://www.chembuddy.com/?left=EBAS&right=ideal-gas-and-concentration-calculator
http://www.lds-vacuum.com/ideal.htm
http://www.monachos.gr/en/calculators/gaseous_state_equation.asp
http://antoine.frostburg.edu/chem/senese/javascript/realgas.shtml
http://www.ajdesigner.com/idealgas/index.php
http://www.pipeflowcalculations.com/reynolds/index.htm
http://ideal.qarchive.org/
http://www.ajdesigner.com/idealgas/ideal_gas_law_temperature_equation.php
http://phoenix.phys.clemson.edu/labs/223/gaslaws/index.html
http://www.chemicool.com/idealgas.html

[Albert]

Looks like a spam message, doesn't it?   

[Borek]

Yep. And chemicool link is duplicated, so it looks even more spammy to me 

[billnotgatez]

I was trying to make a point, but you are right. After looking at this an hour later I thought it was Spam until I saw the author.

[billnotgatez]

The molecular weight and density of common gases
Some values like air may be slightly rounded

http://www.engineeringtoolbox.com/gas-density-d_158.html

It is interesting that the above site has the following definitions
1) NTP - Normal Temperature and Pressure - is defined as air at 20oC (293.15 K, 68oF) and 1 atm ( 101.325 kN/m2, 101.325 kPa, 14.7 psia, 0 psig, 30 in Hg, 760 torr)

2) STP - Standard Temperature and Pressure - is defined as air at 0oC (273.15 K, 32oF) and 1 atm (101.325 kN/m2, 101.325 kPa, 14.7 psia, 0 psig, 30 in Hg, 760 torr)

    * 1 lb/ft3 = 16.018 kg/m3
    * 1 kg/m3 = 0.0624 lb/ft3

We have had many discussions as to the meaning of STP and the confusion it causes for questions in various educational settings

[Donaldson Tan]

You miss out the Standard Ambient Temperature and Pressure (SATP), ie. 25^oC at 1bar, which is often used in Chemical Calculations.