B. A. Burke,' D. A. Davenport, T. J. Smith, and R. A. Walton2 Pwdue University west Lafayette, Indiana 47907
A One-Credit Hour Undergraduate Inorganic Laboratory Course
Commonly encountered inorganic laboratory courses involve both svnthesis and characterization and thevtend to be both sophisticated and time-consuming. We have offered such a course to our maduate students for manv vears and it has proved to he b k h popular and useful. Provided that the necessan, eauioment is accessible to the students and that the department has the necessary financial resources, i t is relatively easy to organize such a course since several texts are already available (1-3) from which to draw suitable experiments. While this type of course is also often appropriate for inclusion in the undergraduate curriculum, i t is best suited to a relatively small class size. Furthermore, most of the published experiments (1-3) are inappropriate for a course limited to a weekly three-hour laboratory format. In this article we discuss a one-credit hour undergraduate inorganic laboratory whirh we feel may provide the type of course others may wish to incorporate i&o their undergraduate curriculum. The style of the course was prompted by the increasine ienorance on the oart of manv of our students of the simplest properties of inorganic molecules. Knowledge of the color, physical state, and reactivity patterns (i.e., 'descriptive chemistry') of even the commonest inorganic chemicals seem to bave been deemed less worthy of remembrance than the esoterica of physical-inorganic chemistry. Clearly a balanced treatment of both aspects is necessary. While students should he able to conjure up the molecular orbital diaeram of. sav. nitric oxide it is absurd if a t the same time they inow nithikg of the appearance, preparation, and simple chemistry of this gas. Almost all undergraduate chemistry programs include a one-semester inorganic chemistry lecture course but in view of the range of inorganic chemistry it is obvious that many important topics are excluded for want of time. While some of the experiments we bave included in the laboratory cover topics which are also covered in the lecture course, others are designed to introduce the student to new material.
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Course Structure The course is offered to juniors and seniors and must be accompanied or preceded by the lecture sequence. I t is required of our chemistry majors. Though it is not specifically directed a t preparing students for graduate work in inorganic chemistry, many of the juniors have been encouraged to elect further inoreanic courses and do inoreanic research as seniors. The stud& are divided intogroups of about 14 and mostly work in oairs. We have been fortunate in havine a t least two instructors present a t all times. In this way continuous interaction is possible and the course becomes more than the sum of its experiments. Since the one-credit hour course occupies three contact hours we have tried to limit outside work and keep write-ups to a funrtiunal minimum. This excludes experiments whirh require time-consuming data collection andmany of those in texts by Angelici (I), Jolly ( 2 ) ,and Adams and Raynor (3) which require more time than We three-hour time slot. De-
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Present address: Department of Chemistry, EL Camina College, Via Torrance, California 90506. Address anv corresoondenee to this author. In the evrnt that the nrcebcan inrtrumentation is unavailable. we rccornnwnd that the itudmta bcdtrected to rhr npvropriatrdors in the literature. I
360 1 Jourml of Chemical Education
tailed spectral characterizations are also impractical if students are required to record their own spectra, so we have made the teaching assistants responsible for obtaining representative mass suectra, nmr soectra. electronic ahsorotion spectra, and low f;equency infrared spectra. These are.then made available to students.?Thc students obtain their own infrared spectra in the 4MX)-6fi0 cm-I region on an instrument directly accessible to them in the laboratory.
Experlrnental Description In this section we present an outline of the experiments. Full details may be obtained from R. A. Walton. (1) Reactions of Metal Ions of theFirst Transition Series Simple test-tube experiments involving reactions of Ti(IV), Cr(III),MnW, Fe(II), Co(II),Ni(II),and Zn(I1)solutions with (11NaOHCaq),(21 NHdaq), (3) conc.HCI,and (4) HsOzare first carried out to remind the students of the ease with which these tran4ion mptal ~vnsmay h~ differentiated with standard chvrn~cnlreagents. 'l'hiq information, ewpled with thr expe. rience gained in vanadium and copper chemistryfrom Experiments (3) and (4),gives the studentsthe necessary background to begin to devise simple chemical tests to deduce the nature "
Tin a n d ~ e o d
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(a) The synthesis of (NH&+C16 and (NH4j2PbC4;(4). (b) Comparative study of the infrqed spectra of these two salts in the region 4000 to 250cm-', including the locationand assignment ( 5 ) af the Sn-CL and Ph-CI stretching vihrations. (c) A studvof thereactions of these twosalts with water and + HgCl,&and I'bCli r HrCI (aq). ofthes&t~ms~n('l. Thir iwrsrlgntmn gives information on the relstite stahilities ulthr d~ilerentoxidnrnm states of time tuo srrmr Comparativestudy ofthe reactionsofnrdium metll, NaISnl. mixtures and copper metal towards glacial acetic acid, liquid ammonia, liquid NzOs andlor mixed ethylacetate-N204. These reactions. whieh are carried out in test tubes. illustrate the relalive ease of manipulating several relatwelv lmplrasant nonaqueous solvents. Adequate h w d space must he awrlahle and considrrable caution should. of course, he exercised to avoid burns. (8) Identification of Unknowns The preceding seven experiments occupy the students for most of the semester. However, the students frequently have periods of spare time which we have found can be used to advantage in identifying inorganic unknowns. Early in the semester they are given a sample of a simple transition metal salt (e.g., CuBrz, KIC~OI,or CoSOd). Each pair of students is provided with a different sample and they are permitted to use only tests employing common chemical reagents and infrared spectroscopy to aid them in this identification. Once this bas been successfully accomplished, a second more complicated inorganic compound (e.g., (n5-CsHs)2TiC12, F~(BCBC)I or [($-CsHs)Fe(C0)2]~) is supplied (these sometimes are byproducts of graduate level inorganic preparation courses), but in this instance any reasonable chemical or physical method can he used by the students. Throughout this assignment the students are encouraged to discuss with the instructors which identification urocedures they think will be most a u ~ r o u r i ate. (9) or Alternative Exoeriments . . Ootional . Clearly, Experiments (1) ihrough (8) will not necessarily be suitable or even possible in a similar one-credit hour course
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whieh may be adopted elsewhere. There are however many others whieh equally well fulfill the necessary criteria, i.e., they are neither time consuming nor expensive and are suitable for relativelv. larae . numbers of students. In addition to several of the experiments which are described in the text hy Pass and Sutrliffe ,101. we have found that the fdkwing nre sutablr: (a1 Preparation and Structural Characterization of Ammonium Henaquovanadium(I1) Sulfate ( I 1 ). (b) Oraanometallie Chemistrv of Mercurv (12) (c) N~ckelCmnplpxea with 0Ganic and ~hbsdhoruvLigands ( I l l -partir~tlarly the synthesis of rq'-CsHi)gNi, rPh#),Ni(:l~, and (nWsH-)N~tPl'h3)Cl.
Acknowledgment T h e award of a Camille a n d H e n r y Dreyfus TeacherScholar G r a n t to R.A.W. is gratefully acknowledged. W e t h a n k Dr. T e r r y E. Dorsett, Mr. Howard D. Glicksman, a n d Mr. Ronald E. Myers for their helpful suggestions concerning improvements i n t h e laboratory course. Literature Cited
1, H.."Plaetical
l n l l r ~ a n i cChemiitrv."Secllnd Editi,m.Chapman
Hsll.Lund
