edited by WALTERA. WOLF Eisenhower College Seneca Falls. NY 13148
Applied Thermodynamics D. Pan Wong California State University. Fullerfon Fulleflon. CA 92634
Which is more efficient in heating water, an electric coffee pot, a microwave oven, or a pot on an electric stove? The microwave oven often wins most of the votes because students have been sold on the idea that i t is best for energy conservation in cooking. Experiments show that in heating 2 cups of water in a 6-cup Sears@Kenmore electric coffee pot, in a S e a r k Kenmore microwave oven, or on the to^ of an electric stove. the coffee pot is the most efficient, the stove second, and the microwave oven third. Efficiencies were calculated hv comoarinr- heat absorbed by the water to the energy input: The First Law of Thermodynamics explains the high efficiency of the coffee pot because energy in the form of heat is transferred directly from a hot to a cold object which are in physical contact. Except for the energy lost to the container, the energy transfer should be 100%efficient. The Second Law says that you can never win; you cannot even break even. I t explains the low efficiency of the microwave oven. in which electrical enerw is first converted to microwave'energy then to heat energy. While the efficiency in converting- microwaves to heat is 88%.in this case the conversion of electrical to microwave rnergv is only 13.Iwc etiicient. The Electricstwe lodes heat to theair, to thestove itsrlf. and to the heat capacity of the pot. A conventional oven is even more inefficient because heat is conducted by air. Calculations of those efficiencies are available upon request.
in'this method is the exploitation of the electrophilic behavior of the coordinated nitric oxide group. The linearly bound M-N-0 ..mouD. mav, be assumed to contain "NOf". which can react with strung alkali to pnnluce NO;.The formation of NO; can br effectivelv teited hv using Grirss's rrarentl (0.002% N-(l-naphthy1)'ethylene diamiie d i h y d r o c h h l e and 0.5% sulfanilic acid in 2.3 M acetic acid) provided complexes under study do not contain any NH~OH,NO;, or NO, ligands. The complexes are decomposed in alkali and acetic acid (6 M )and Griess's reagent is added to the cold solution. An ,,,A( instantaneously formed, deep reddish-violet colorat~on 520 nm) indicates the presence of coordinated nitric oxide. This method lends positive evidence of the nitrosyl group, and a few examples are presented in the table.2
' Griess. P.. Ber.. 1 2 , 4 2 7 (1879).
Subramanian, Ph.D. Thesis (1981). Indian Institute of Technology, Kanpur, India.
Test for Presence ot Coordinated Nitrosvl Grouo CObr in alkaline medium
Color on acidification with dil. acetic acid
Color on addition of Griess's reagent
NadFe(NOMCNk1
Pale yellow
Green
Ks[Cr(NOnCN)sl
Pale yellow
Yellow
K~~MniNOliCNlsI
Colorless
Colorless
[Re(N0Mbi~~)Cld
Colorless
Colorless
Perlyasamy Subramanian and Sabyasachl Sarkar
[Mo(NO)~CI~(PY)~I
Colorless
Colorless
Indian lnstbtute of Technology, Kanpur-208 016, India
[(C~Hs)~Nl~[MD(NO)~iox)~I Colorless
Colorless
Ko[M~iNO)i~x)rl
Colorless
Colorless
[Mo(NO)CllwhenhlCI
Colorles~
Colorless
[W(NO)~CIz(4rhl
Colories~
Colorless
Deep reddish violet Deep reddish violet Deep reddish violet Deep reddish violet Deep reddish "lolet Deep reddish videt Dsep reddish violet Deep reddish violet Deep reddlsh violet
Rapid Chemical Identification of the Nitrosyl Group in Complexes
The most widely used method to identify the coordinated nitrosyl group is its characteristic IR absorption band. However. when coordinated carbonvl and carboxvlate erouns .. . are present in the complexes, such identification Iwcomes difficult. The followine s i r n ~ l echemical test enables r a ~ i didentification of coordynated nitric oxide. The principleinvolved
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Compound
Volume 59 Number 6 June 1982
527
