Basic Thermodynamics ~ J. Pohl © | www.THERMOspokenhere.com (90-B680) |

More substances **are not** ideal gases than are. Thus the equation can be used "after the gas has been shown to have ideal behavior" or "by assumption that the equation applies."

**Is water at STP an ideal gas?**

♦ The standard pressure and temperature are: p = 101 kPa and T =25°C respectively. We are also aware that water is a liquid (not a gas) at STP and that the specific volume of the liquid is v = 1.0 cm³/g. For water to qualify as an ideal gas its properties when placed in the Ideal Gas Equation, arranged as below, must equal 1, or be very close to "1".

NOTE: this is the only time we warp the Ideal Gas equation. The purpose is specific.

(1) (1) |

So put the numbers in the equation and make sure the units are correct.

(2) 2 |

**Obviously!** We knew to begin that water is not a perfect gas.

More substances **are not** ideal gases than are. Thus the ideal gas equation can be used ONLY "after the gas has been shown to have ideal behavior" or "by assumption that the equation applies."

**Is water at STP** an ideal gas?