JOHNJ. ALEXANDER University of Cincinnati Cincinnati. Ohio 45221
Leon S. Clereszko University of Oklahoma Norman, OK 73019
The following "problems" were written many years ago for use by teaching assistants in general chemistry courses. They are analogs of prohlems used in beginning courses. Getting awav from chemical terminolozv. which frightens some studen&, can show them that pr;;dlems in cgemistry are not different from others involving simple arithmetic. Question 1 is analogous to the percentage composition calculation for sulfur in anhydrous sodium sulfate, substituting ham for sulfur, and so on, in making what might be a ridiculous sandwich. Question 2 requires the recognition of weight relationships in the equation 2 slices bread
+ 1slice ham + 4 pickles yields one sandwich
Question 3 is analogous to a Charles' Law calculation. Some of the "humor" imbedded in the oroblems mav be dated or beyond the freshman. Some of the &stants whodid not read the oroblems before thev. . eave the auestions to the class were a l k l e surprised.
Questions 1, A certain kind of snndwrrh rs mnde fnm twaxliresof bread, one r l m dhnm, nnd fwr pwkles. Whnr percrnmge hy weight is ham ~f thr wrighr of aslicr oi bread is 2:i y , aslirr of horn wigha32 g and a pickle 16 g? 2) How many grams of bread are required to make sandwichesfrom 256 grams of ham according to Problem I?
402
Journal of Chemical Education
31 In mnccrtmp,his specialty, rhe Tolstor romhie, for export, Alexei Karenin, inside man at rhr S u m Kroun D~stlllery,follwm "Chuck's Lwx,"which IS based on stlr~staal rewarrhes and old wives' tales. "Chuck's Law" requires that for "the flavor that never tires," the amount of water added per barrel must he varied according to the temperature of the importing locality. To insure the best results, the amount of water added is increased by 11273rd for every degree by which the temperature exceeds O T and decreased by 11273rd for every degree below 0°C. The "Laika Inn" at Novosibirsk gets a grade of products referred to a3 "Vat 597" containing 597 ml of water per barrel, appropriate to the local temperature which averages -65'C. What should he the amount of water added oer barrel of the brvrragr intended for rxpon tc, "Nnpuh's Alley" at Gizeh, whew theawroyr temprrnrurr in theshnde uf the pyram~duis ~
~
~
~~
:,Yo(:?
Acceptable Solutions 1) Total weight of ingredients 2 bread = 46 g 1 slice ham = 32 e" 4 pickles = %ham =
%?%?& = 22% 142 g 46 g bread
X 256 g ham = 512 g bread 23 g ham 3) Suppose y ml are added at 0% Then, if temperature is -65'C, we know that:
2) We have
at +39"C, the amount added is
