The author replies to Tóth.
The chemical equation proposed and brilliantly
discussed by Z. Tóth, referring to the electrolytic production
of iodoform (a quotation would have been helpful),
exhibits quite interesting stoichiometric features.
Clearly, it is not a multiple-stoichiometry
equation, since five nonequivalent atomic conservation relations
are available to assign the six stoichiometric coefficients, so
that it can be readily balanced by the algebraic method
(1). The same is no more true when employing the (traditional)
oxidation-number method, because ethanol gives origin to
two different oxidation products (each containing carbon with
a different oxidation number) such that the ratio of
their amounts (numbers of moles) cannot be established
a priori. Minor difficulties arise from the facts that the (only)
reduction product (formally) takes origin from two different
species, one of which is also the source of the oxidation
products; furthermore, in this equation, hydrogen plays a
dual function (2), partly behaving as a redox, and partly as a
non-redox, element.
Therefore, Tóth's equation represents a third
case where, while the traditional oxidation-number method
fails, our approach, which splits the equation into two
simpler ones, each involving the participation of the same
"extraneous" species as co-reactant and co-product, succeeds;
the other two cases are the double disproportionations
(3) and the rather uncommon equations of the kind elsewhere
(4) discussed by us, for which we would propose the name
of dis-co-proportionations.
Finally, we would observe that Tóth's equation
could have been balanced also by employing the recently
published (5) more general version of the
oxidation-number method which makes use of oxidation-number concepts
in an algebraic-method framework.
Literature Cited
1. Porter, S. K. J. Chem.
Educ. 1985, 62, 507-508.
2. Kolb, D. J. Chem. Educ.
1978, 55, 326-331.
3. Cardinali, M.E.; Giomini, C.; Marrosu, G.
J. Chem. Educ. 1995, 72, 716.
4. Giomini, C.; Marrosu, G.; Cardinali, M. E.
Educ. Chem. 1994, 31, 67.
5. Cardinali, M. E.; Giomini, C.; Marrosu, G.
Educ. Chem. 1996, 33, 51-52.
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