Help please with questions about gases and the ideal gas equation?

Question

1) When using the ideal gas equation how do I know if the gas to be plugged into is "ideal" or real"? If it is a real gas then I gues Pv=nrt cannot be used?

2) does Pv=nrt actually compare gases to STP using the R constant?

Answer 1

Assume all gases are ideal at the temperature and pressure you will be using.

The constant R must match the units you are using-

R = 0.082057 liter atm / mol K

R = 8.3144 J / mol K

R = 1.987 cal / mol K

Use of PV=nRT allows you to calculate one of the variables (P or V or T or n) when the other 3 variables are known.

STP means "Standard" "Temperature" and "Pressure"

T= 273.15 deg K (0 deg C)

P = 1 atm (which is 760 mm Hg or 760 torr)

Answer 2

1.  The ideal gas law is based on a model of gas molecule behavior.  For a given compound, if this model does not appear to be followed, the gas won't be ideal.  There are several "non-ideal" gas formulas, which "correct" the ideal gas law for non-ideal behavior.  For most gases at moderate pressure (say 10 atm or less) and temperatures less than 1/2 the "critical point", a temperature and pressure coordinate, unique for each compound, where the transition from liquid to vapor occurs with no added heat,  gases do behave close to ideally.  

  

2.  Yes, R is based on the STP volume of a mole of gas.

Answer 3

1...PV=nRT doesn't HAVE to be used in the first place.

The 'Combined Gas Law'  which is a combination of Boyle, Charles and g*y Lussac's Laws will give the exact same answer for any change in a gas parameter.

PV=nRT is derived from these 3 Laws.

2. The combined Gas Law also compares gases to STP parameters.

(Thumbs downer, give me a relevant question and, I'll prove my statements. Can you prove your veto of my answer ???).

Answer 4

Well, in theory nothing is perfect. There is always a little bit of disparity .. and for any gas to make calculations you have to assume tht it is ideal

and no R is used regardless whether the gas is at STP or not

STP merely refers to P = 1 atm, T = 273 K or 0 C

hope tht helps