Page 52 - Physical Chemistry

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surroundings; walls (rigid versus nonrigid; permeable versus impermeable; adiabatic
versus thermally conducting); equilibrium (mechanical, material, thermal); state func- Problems
tions (extensive versus intensive); phase; and equation of state.
Temperature was defined as an intensive state function that has the same value for
two systems in thermal equilibrium and a different value for two systems not in ther-
mal equilibrium. The setting up of a temperature scale is arbitrary, but we chose to use
the ideal-gas absolute scale defined by Eq. (1.15).
An ideal gas is one that obeys the equation of state PV nRT. Real gases obey
this equation only in the limit of zero density. At ordinary temperatures and pressures,
the ideal-gas approximation will usually be adequate for our purposes. For an ideal gas
mixture, PV n RT. The partial pressure of gas i in any mixture is P x P, where
tot
i
i
the mole fraction of i is x n /n .
tot
i
i
Differential and integral calculus were reviewed, and some useful partial-derivative
relations were given [Eqs. (1.30), (1.32), (1.34), and (1.36)].
The thermodynamic properties a (thermal expansivity) and k (isothermal com-
pressibility) are defined by a (1/V) (
V/
T) and k (1/V) (
V/
P) for a sys-
P
T
tem of fixed composition.
Understanding, rather than mindless memorization, is the key to learning physi-
cal chemistry.
Important kinds of calculations dealt with in this chapter include
• Calculation of P (or V or T) of an ideal gas or ideal gas mixture using PV nRT.
• Calculation of the molar mass of an ideal gas using PV nRT and n m/M.
• Calculation of the density of an ideal gas.
• Calculations involving partial pressures.
• Use of a or k to find volume changes produced by changes in T or P.
• Differentiation and partial differentiation of functions.
• Indefinite and definite integration of functions.

FURTHER READING AND DATA SOURCES

Temperature: Quinn; Shoemaker, Garland, and Nibler, chap. XVIII; McGlashan,
chap. 3; Zemansky and Dittman, chap. 1. Pressure measurement: Rossiter, Hamilton,
and Baetzold, vol. VI, chap. 2. Calculus: C. E. Swartz, Used Math for the First Two
Years of College Science, Prentice-Hall, 1973.
r, a, and k values: Landolt-Börnstein, 6th ed., vol. II, part 1, pp. 378–731.

PROBLEMS

Section 1.2 1.4 Explain why the definition of an adiabatic wall in Sec. 1.2
1.1 True or false? (a) A closed system cannot interact with its specifies that the wall be rigid and impermeable.
surroundings. (b) Density is an intensive property. (c) The 1.5 The density of Au is 19.3 g/cm at room temperature and
3
Atlantic Ocean is an open system. (d) A homogeneous system 3
1 atm. (a) Express this density in kg/m .(b)If gold is selling for
must be a pure substance. (e) A system containing only one
$800 per troy ounce, what would a cubic meter of it sell for? One
substance must be homogeneous. 1
troyounce 480grains,1grain 7000 pound,1pound 453.59g.
1.2 State whether each of the following systems is closed or
open and whether it is isolated or nonisolated: (a) a system en- Section 1.4
closed in rigid, impermeable, thermally conducting walls; (b) a 1.6 True or false? (a) One gram is Avogadro’s number of
human being; (c) the planet earth. times as heavy as 1 amu. (b) The Avogadro constant N has no
A
units. (c) Mole fractions are intensive properties. (d) One mole
1.3 How many phases are there in a system that consists of of water contains Avogadro’s number of water molecules.
(a) CaCO (s), CaO(s), and CO (g); (b) three pieces of solid
3 2
AgBr, one piece of solid AgCl, and a saturated aqueous solu- 1.7 For O , give (a) the molecular weight; (b) the molecular
2
tion of these salts. mass; (c) the relative molecular mass; (d) the molar mass.