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preface to fifteenth edition

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PHYSICAL PROPERTIES 5.169<br />

TABLE 5.30<br />

Triple Points of Various Materials (Continued)<br />

Substance Triple point,K Pressure,mmHg<br />

Phosphorus,white 863 32 760<br />

Plu<strong>to</strong>nium hexafluoride 324.74 533.0<br />

Propene 103.95<br />

Radon 202 500<br />

Rhenium dioxide trifluoride 363<br />

Rhenium heptafluoride 321.4<br />

Rhenium oxide pentafluoride 313.9<br />

Rhenium pentafluoride 321<br />

Succinonitrile (NIST standard) 331.23<br />

Sulfur dioxide 197.68 1.256<br />

Tantalum pentabromide 553<br />

Tantalum pentachloride 489.0<br />

Tungsten oxide tetrafluoride 377.8<br />

Uranium hexafluoride 337.20 1 139.6<br />

Water 273.16<br />

Xenon 161.37 612<br />

5.9.1 Some Physical Chemistry Equations for Gases<br />

A number of physical chemistry relationships,not enumerated in other sections (see Index),will be<br />

discussed in this section.<br />

Boyle’s law states that the volume of a given quantity of a gas varies inversely as the pressure,<br />

the temperature remaining constant. That is,<br />

constant<br />

V or PV constant<br />

P<br />

A convenient form of the law,true strictly for ideal gases,is<br />

PV PV<br />

1 1 2 2<br />

Charles’ law, also known as Gay-Lussac’s law, states that the volume of a given mass of gas<br />

varies directly as the absolute temperature if the pressure remains constant,that is,<br />

V constant<br />

T<br />

Combining the laws of Boyle and Charles in<strong>to</strong> one expression gives<br />

PV<br />

T<br />

PV<br />

<br />

T<br />

1 1 2 2<br />

1 2<br />

In terms of moles, Avogadro’s hypothesis can be stated: The same volume is occupied by one<br />

mole of any gas at a given temperature and pressure. The number of molecules in one mole is known<br />

as the Avogadro number constant N A.<br />

The behavior of all gases that obey the laws of Boyle and Charles,and Avogadro’s hypothesis,<br />

can be expressed by the ideal gas equation:<br />

PV nRT

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