Suggested solutions to exercises

Aqueous solutions of compounds containing the Cu2+ ion are blue as a result of the presence of the Cu(H,0)62+ complex. Does this complex absorb in the visible region Suggest an explanation. Refer to Major Technique 2, which follows these exercises. 

For other cases, such as La3+ where more detail is required about the nature of the species present in solution, titration data can be computer fit to more complicated multi-equilibrium models containing Mx 1 v( OR)v forms whose stoichiometry is suggested by information gained from independent spectroscopic or kinetic techniques. One must be mindful of the pitfalls of simply fitting the potentiometric data to complex multi-component models for which there is no independent evidence for the various species. Without some evidence for the species put into the fit, the procedure simply becomes an uncritical mathematical exercise of adding and removing various real and proposed components until the goodness of fit is satisfactory. 

Finally, you can end your essay by suggesting a specific action that your readers should take. As with the solution or recommendation strategy, this one is also used often in business writing. Here s an example of a conclusion for the essay about television and lack of exercise. Notice how it frames the essay by referring to the opening line of the introduction. 

Results from the two experiments conducted on the aldehydes and ketones are listed in Table III as separate sets of data to illustrate the care that must be exercised in conducting and evaluating these runs. Both C02 extractions were performed under similar conditions. However, in the second run, the U-tube traps were contacted with the 2,4-dinitrophenylhydrazine derivatizing solution for longer periods of time. This modification in the analytical procedure permitted higher total mass accountabilities in the second experiment, ranging from 64.9% for isophorone to 28.7% for methyl isobutyl ketone. The recoveries from the raffinate for each of these compounds remained relatively constant. This result suggested that the trap recoveries in the first case were artificially low. 

Exercise 13-11 Suggest a mechanism to show how the following compound may be formed by irradiation of a solution of c/s-butenedioic anhydride (maleic anhydride) in benzene ... 

There is a myriad of analytical solutions for steady-state conduction heat-transfer problems available in the literature. In this day of computers most of these solutions are of small utility, despite their exercise in mathematical facilities. This is not to say that we cannot use the results of past experience to anticipate answers to new problems. But, most of the time, the problem a person wants to solve can be attacked directly by numerical techniques, except when there is an easier way to do the job. As a summary, the following suggestions are offered ... 

We will later consider the approximation that affects the transition from Eq. (4.4) to Eq. (4.6) in detail. But this result would often be referred to as first-order perturbation theory for the effects of - see Section 5.3, p. 105 - and we will sometimes refer to this result as the van der Waals approximation. The additivity of the two contributions of Eq. (4.1) is consistent with this form, in view of the thermodynamic relation pdpi = dp (constant T). It may be worthwhile to reconsider Exercise 3.5, p. 39. The nominal temperature independence of the last term of Eq. (4.6), is also suggestive. Notice, however, that the last term of Eq. (4.6), as an approximate correction to will depend on temperature in the general case. This temperature dependence arises generally because the averaging ((... ))i. will imply some temperature dependence. Note also that the density of the solution medium is the actual physical density associated with full interactions between all particles with the exception of the sole distinguished molecule. That solution density will typically depend on temperature at fixed pressure and composition. 

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