Liter-atmosphere

So far, so good. The situation is really no different, say, than the ideal gas law, in which the gas constant is numerically different and has different units depending on the units chosen for p and V, The unit change in Example 10.1 is analogous to changing the gas constant from liter-atmospheres to calories it is apparent that one system is physically more meaningful than another in specific problems. Several considerations interfere with this straightforward parallel, however, and cause confusion ... 

Angstrom units Meters 1 X 10- Calories, gram Liter-atmospheres 4.1.30 X 10"-... 

B.t.u. liter-atmospheres 10.41 Cubic centimeters Quarts (U.S. fluid) 0.0010567... 

B.t.u. per minute Horsepower 0.02.357 Cubic foot-atmospheres liter-atmospheres 28.316... 

R is obtained in joules per kelvin per mole R = 8.314 J-K-1-mol" Table 4.2 lists the values of R in a variety of different units which are useful if volume or pressure is reported in other than SI units. For instance, it is sometimes convenient to use R in liter-atmospheres per kelvin per mole R = 8.206 X 10 "2 L-atnvk -mol... 

Therefore, if we work in pascals and cubic meters, the work is obtained in joules. However, we might have expressed the pressure in atmospheres and the volume in liters. In this case, we may need to convert the answer (in liter-atmospheres) into joules. The conversion factor is obtained by noting that 1 L = 10 3 m3 and 1 atm = 101 325 Pa exactly therefore... 

SOLUTION We use Eq. 3 to calculate the work, and then convert liter-atmospheres into joules. 

Calculate the conversion factor for changing liter atmosphere to (a) erg, (b) joule, and (c) calorie. Calculate the conversion factor for changing atmosphere to pascal and atmosphere to bar. 

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