“Consider lab drawer’s Bunsen burner…
Providing new role for chem learner
(Through method, flame-testing,
Steps towards metal-guessing):
Of cation’s ID, discerner.”
The 7 April 2021 limerick summarized a qualitative analysis technique often used in introductory chemistry, which employs one of its most memorably named instruments, the Bunsen burner.
“Consider lab drawer’s Bunsen burner… /
Providing new role for chem learner…”
Combustion can occur completely or incompletely. Complete (stoichiometric) combustion is what is taught in the textbooks: a hydrocarbon fuel reacts with oxygen and is converted fully to carbon dioxide and water. The path from start to finish actually occurs via a wide network of complex reactions involving radicals, which are species with unpaired electrons; these can cause all sorts of side reactions and products. When the combustion is incomplete, these side reactions include the formation of soot. Soot has many detrimental effects, and Robert Bunsen (1811-1899) was interested in developing a burner that could produce a particularly clean flame, avoiding these effects. His burner has been widely adopted for use in introductory chemistry laboratories (by “chem learner[s]”).
“(Through method, flame-testing, /
Steps towards metal-guessing): /
Of cation’s ID, discerner.”
A traditional and interesting use of the Bunsen burner is the flame test, or “method, flame-testing.” A wire is placed into a solution made from an ionic compound, which includes a cation derived from a metal of interest. The wire is then placed into the flame, and as the ionic solution evaporates, the flame will turn a certain color based on the emission characteristics of the metal ion in question. For instance, copper would turn the flame a bluish-green, and potassium would turn the flame violet.
If a student is given an unknown compound and asked to determine the cation in this compound, they could use the flame test behavior as a step towards identifying the unknown; their role as “chem learner” could then also include being “of cation’s ID, [a] discerner.”
Chemphasis 