chapter  2
14 Pages

Properties of Gases and Vapors

The first quantitative data regarding the behavior of gases were reported by Robert Boyle in 1662. He showed that at any given temperature, the product of the pressure

P

exerted by a gas and its molar volume

v

is constant. In 1787, Jacques Charles observed that this constant is a function of temperature. Thus, the equation of state for one mole of a gas was determined to be

Pv = f

(

t

) (2.2)

It was found that

f

(

t

) was approximately linear:

f

(

t

) =

a

+

bt

. The constants

a

and

b

were estimated from experimental data. In units of liters per mole and atmospheres, an expression for

f

(

t

) was determined:

f(t)

= 22.4140 + 0.082057

t

= 0.082057 (273.16 +

t

) (2.3)

where

t

is the temperature in degree Celsius (or Centigrade). This expression can be rewritten if a new temperature scale is adapted such that

T

= 273.16 +

t

°

C. We then have, for one mole of a gas,

Pv = RT

(2.4)

where

T

is the absolute temperature and

R

is the universal gas constant whose numerical value depends on the choice of units. Table 2.1 gives the values of

R

in different sets of units.