A Working Method Approach for Introductory Physical Chemistry Calculations by Brian Murphy, Clair Murphy, and Brian J. Hathaway

Reviewed by Hugh Cartwright Physical and Theoretical Chemistry Laboratory , South Parks Road, Oxford University, Oxford, England OX1 3QZ Hugh.Cartwright@chemistry.oxford.ac.uk

A Working Method Approach for Introductory Physical Chemistry Calculations. The Royal Society of Chemistry. ISBN 0-85404-5534-8. 152 pages.

The authors of A Working Method Approach for Introductory Physical Chemistry Calculations have a laudable aim. Recognizing the difficulty that many first-year chemistry students have with calculations, they have set out to guide students through calculations using a logical stepwise approach.

The book is almost entirely devoted to problem solving, with only a brief overview of some aspects of physical chemistry, which is included as background material. While the working-method approach seems to amount to little more than exhortations to use a logical approach to problems, there are plenty of examples for students to read through, study, and practice on, and most teachers would endorse the attempt to persuade students to work logically.

Unhappily, though the aims of the authors are praiseworthy, the book itself is not. A number of serious problems exist, which are of such magnitude that the book is more likely to confuse than illuminate. Most notable is the poor quality of the figures. These are simple line drawings, but the authors appear to have done little to ensure that they are correct. For example:

Figure 1.2 shows the three phases of matter in diagrammatic form. The figure is supposed to illustrate that "ordered structure [in the liquid phase] is not as evident [as in the solid phase]." However, the liquid phase, drawn as a series of blobs in a box, is highly ordered, with just a single blob not contributing to an entirely regular structure. The figure thus fails to illustrate the degree of disorder in liquids.
Figure 1.2 is referred to later, when it is claimed that "the tiny particles appear to be moving at random, as shown in Figure 1.2(c)." However, the figure gives no indication that the particles are moving at all, randomly or otherwise.
Figure 5.2 shows three titration curves that are simply wrong. The titration curve of a strong acid against a strong base, for example, is drawn as three straight lines, whose gradient changes abruptly where one line meets the next. The section of line passing through the equivalence point is also far from being nearly vertical. Two further titrations are constructed from straight lines. This is grossly misleading.
While Figure 5.2(b) suggests that pH rises on addition of base, immediately below it, Figure 5.2(c) shows pH falling as base is added.
Figure 6.5 shows a hydrogen electrode. The drawing is so sparse that it is not clear that the electrode must be in contact with both gas and solution.
Figure 8.3 purports to illustrate half-lives. The plot of concentration as a function of time consists of two straight lines connected by a short curved section. Again this does not accurately represent the behavior of real systems. In addition, the time at which the concentration falls to half its initial value is incorrectly shown.

These are serious problems, but further problems exist in the body of the text. For example:

Different values for Avogadro's constant are given on successive lines.
The halogens are described as forming Group 17 of the periodic table.
The pressure calculated in a sample calculation is expressed in units of cubic centimeters.
Eight lines after the equation PV = nRT is introduced, we are told that PV = nRDT, the implication being that the temperature may change without the values of the other variables responding.
The authors claim that standard enthalpies of formation refer to 298 K, and enthalpies of combustion to a temperature of 273 K. Two pages later, they use enthalpies of formation to calculate an enthalpy of combustion without commenting on the fact that (according to their definitions) the values must be corrected for the differing standard states.
A sample calculation on gas-phase reactions contains a serious elementary error. This is hardly what one would expect in a book devoted to showing students how to make a success of their calculations.
After one calculation, the authors state, "the temperature could have been left in degrees C, but it is good practice always to convert the temperature to the absolute temperature...." The authors have chosen a poor example with which to make this justifiable point. If they had indeed used the temperature in degrees C, as they suggest is permissible, the calculations fails immediately.

This book could have met a real need in the teaching of physical chemistry. Given a thorough rewrite, it might still do so, but at present the errors it contains are so severe that I would not suggest my own students buy a copy, and reluctantly I cannot recommend it to others.