Fresenius Z. Anal. Chem. 297, 271 -277 (1979) Fresenius Zeitschrift fiJr

�9 by Springer-Verlag 1979

International Student Competitions in Analytical Chemistry*

Vilim Vajgand

University of Belgrade, Faculty of Science, Department of Chemistry, P.O. Box 550, YU-I1000 Belgrade, Yugoslavia

Internationaler Studentenwettbewerb in Analytischer Chemic

Zusammenfassung. Die Vorteile eines Wettbewerbs als Anregung zu besonderen Leistungen werden diskutiert und der internationale Wettbewerb ffir Anatytische Chemic, wie er in Belgrad durchgefiihrt wird, wird im einzelnen beschrieben.

Summary. Competition can play a very positive role of university, stimulating students to extra efforts. The international student competition in Analytical Chemistry as performed at Belgrade university is discussed in detail.

Key words: Analytische Chemic; Studentenwettbewerb (Belgrad).

The International Student Competition in Analytical Chemistry (ITAH) is held every year as a part of Student's Day celebration on April 4th at the Faculty of Science in Belgrade.

Competition in Analytical Chemistry began in 1968, when 3 teams from 3 Yugoslav universities took part in them, but since 1970 all Yugoslav universities have been included. From 1972 the competitions have become international. In the last few years about 20 teams have been regularly taking part in the com- petitions, 7 of them from foreign countries. Each year there are about 80 competitors in all.

* Presented at Euroanalysis III conference, Dublin, August 20-25, 1978

Among the foreign teams, the Hungarians took part seven times; almost all Hungarian universities at which Analytical Chemistry is lectured were included in the competition. There were also several teams from Poland (from the universities of Warsaw, Wroclaw, Poznan, Lodz and Torah). Teams from Sofia, Prague, Rome, Munich and Timi~oara also participated in this manifestation. The competition in Analytical Chemistry became an international manifestation whose results are favourably commented by many scientists [2].

The competition consists of the theoretical and practical part. In the theoretical part competitors have to solve 25 problems. The questions are given in written form; they are the same for all participants and for their solution 150min are provided. The practical part consists of the determination of Ca and Mg in a mixture by complexometric titration. The time given is 150 rain. The answers to the questions and results in practical part are evaluated by the international jury which consists of all leaders of the teams. The list of members of the jury since 1972 includes 74 names, some of them having been members several times.

The introduction of competitions in Analytical Chemistry at university level became popular in Yugoslavia as well as in participating countries ; the rise of interest and the percentage of gained points in the theoretical and practical part can be seen in Table 1. The total number of competitors so far is 697 (565 at the international competitions 1972- 1978) and 132 at the Yugoslav competitions (1968-1971). Competitors from Belgrade, Zagreb, Ljubljana, Warsaw, Szeged and Veszprtm were best in the individual rank; in teams' competition the most successful were those from Belgrade, Zagreb, Szeged, Budapest, Ljubljana and Veszprtm.

The competitions are unique because they are organized by students. Most of the students took part

0016-1152/79/0297/027l/$01.40

272 Fresenius Z. Anal. Chem., Band 297 (1979)

Table 1. Competitions at university level. Yugoslav federal and International Competitions of Students in Analytical Chemistry ("ITAH")

Year of No. of compet. No. of compititors Number of teams Percentage of points compet, gained in

Yug. Int. totaI foreign total foreign theoret, practical (non-Yug.) (non-Yug.) part part

1968 I - 18 - 3 - 45.6~ 36~ 1969 II - 15 - 5 - 40.1 55 1970 III - 49 - 11 - 23.2 27 1971 IV - 50 - 12 - 26.2 35.7

1972 V I 74 3 16 1 26.1 44.7 1973 VI II 87 23 19 6 14.0 39.3 1974 VII III 67 13 14 3 21.9 52.8 1975 VIII IV 111 41 25 9 26.2 59.1 1976 IX V 90 33 29 11 26.9 51.6 1977 X VI 89 30 28 10 27.0 56.3 1978 X I VII 47 24 14 8 28.5 59.9 Average: 81 24 21 7 24.4 52.0

in competitions while in primary and secondary schools. They joined their students' club "Sima Lozani6", in 1968 they accepted my idea to organize competitions in Analytical Chemistry. A favourable coincidence was that I was lecturer of Analytical Chemistry at 3 universities at the same time and therefore could make the first steps to select the best competitors, a total of only 18. After a good accep- tation at other universities, there already were about 50 students in 1970 from most Yugoslav universities and, since 1972 the competition became an international one. This competition on university level is unique also in another sense, because it is the only one for students in chemistry.

A question very often raised was : are competitions a valuable form of cooperation among the youth, or should they be replaced by other activities? Our experience confirmed that competitions were of great value not only for elementary and secondary school pupils, but for university students too. Competitions in Analytical ChemistrY are a novelty in teaching at university level because they offer possibilities for real evaluation of knowledge of competitors, their speed in problem-solving and psychological stability during accomplishment of the theoretical part, and it also allows them to show skills in the practical part. Competition encourages the most talented to make greater efforts and to obtain greater appreciation for their work than in the normal university studies. In this way the competition represents one possibility of education of top rank chemists. One member of the jury pointed this out clearly: "We have so far been trying to direct talented students only towards research, to seminars and to symposia. We have not been realizing that competitions offer wide and challenging chances

No of items

80 L

60-

40-

20-

0 20 40 6o 80 lOO % of answers

given per items

Fig. 1. Difficulty level of items. Abscissa - ~ of answers given per items; ordinate - number of items; total number of items 440; classes formed from 10 ~ intervals (ranges)

for activating the best students, for individual stimu- lation and for offering the opportunity to the most talented among young people to compare themselves". Competitions can serve even as a new form of in- ternational cooperation in education of most talented students. The student's competitions in Analytical Chemistry confirm this.

Analytical Chemistry is really the only part of chemistry which allows the collection of a large number of competitors interested in chemistry, no matter whether the competitors are studying chemistry or related fields of science, like agriculture, pharmacy, medicine, mining etc. Analytical Chemistry provides a link with all other parts of chemistry, has a leading role in education and plays an important part in practice. Therefore, the determination of Ca and Mg in a mixture, as included in the practical part of the competition, is important not only to the chemist, but also to others interested in forestry, geology etc.

V. Vajgand: International Student Competitions

Table 2. Competition items

273

Topic Number Mean Range of value % items 2

Relative* average deviation

Group A Qualitative analysis Chemical equations Stoichiometry + gravimetry Gas analysis

Group B Equilibrium constants Concentr. from equil, const. pH and cH + Solubility and Sp Complexes Extraction

Group C Prepar. of solutions Volumetric analysis Potentiometry (Redox proc.)

Group D Electrolysis + conductometry Optical methods Chemical kinetics Thermochem. + phys. meth.

Group E Statistical methods Graphical methods (present)

81 34.8 9 45.3 2--83 53.4

2l 40.0 12 - 83 42.2 38 32.9 1-94 48.6 11 28.7 0-68 49.8

148 28.8 14 31.9 4-67 42.1 13 23.0 0-40 59.0 61 34.3 0-94 48.4 31 33.5 0-63 49.0 23 10.3 0-28 64.2 5 34.2 11 - 69 50.9

86 27.1 17 45.7 0-87 37.6 37 26.9 1-72 63.8 32 17.6 1-49 69.9

76 22.1 38 17.3 0-67 58.9 21 27.9 0-67 56.6 9 22.6 0-56 56.6

14 16.7 4-34 41.9

56 18.4 13 24.0 0.5-78 79.2 43 16.6 0-72 79.5

*Relat. aver. dev. - aver. deviation

~. 100 mean value

Variation coefficient

1.25 .100

Some Professional Aspects of Competitions

The problems given in the theoretical part did not have the aim to get information about facts which had been memorized by competitors. Often, all necessary facts, even the formulas were given (for example in problems concerning extraction, statistics etc.). The main goal was to get an insight in the competitors' ability to solve the problem. Problems were given as an entity or divided into parts, in order to follow up the ability of the competitor to cope with them.

The given problems were in general difficult. I have chosen mainly such problems that can differentiate the best among the competitors. From the 266 problems with 440 questions (items) during 11 years, the winners solved only 64 % on the average. That means that even for the best competitors 1/3 of the items were either uncommon or unsolvable in the given time. On the average the competitors solved 27 % of the items and gave wrong answers for 24 ~ , while 49 % of the items were without answer. In other words, competitors had to cope with more complex problems then they usually do and have chosen to answer first problems which are easier and then the problems of increasing difficulty.

The limiting factors were, except the knowledge, the speed in which they could solve the problems. According to the findings of Eysenck [1], a linear relationship exists between difficulty level of the test item and logarithm of the time necessary for problem- solving. The speed in attaining the correct answer is therefore the main difference in measuring kinds of intelligence.

Trends in difficulty levels of items can be followed by the percentage of solved items. Therefore, the percentage of positively answered items were classified in intervals of 10~. The maximum of the curve obtained lies in the range with 1 0 - 2 0 % positively answered items, while facile items were rare and were given only in order to compare the results achieved with results obtained under normal conditions in the cur- riculum (Fig. 1).

What was the knowledge of competitors in various fields of Analytical Chemistry and related topics ? This investigation was undertaken to find out relations between the percentage of correctly answered items and the topics which they belonged to. The distinction of items according to topics is rather arbitrary because some of them were combinations of two or more topics.

274

Table 3. Selected competition problems

Fresenius Z. Anal. Chem., Band 297 (1979)

Percentage of correct answers :

YI/1. Put chemical formulas in place of the letters A to H in the given scheme :

+A

-A

+o

- C

Answers: A = H20 (0.5 points), B = Ca(OH)2 (0.5p.), C = CO2 (0.5p.), D = CaCO 3 (0.5 p.), E = Ca(HCO3)2 (0.5 p.), F = H2C204 (0.5p.), G = CaC20 4 (0.5p.), H = CO (0.5) 16.7%

VI/14. 117.0 mg of NaCI are dissolved in 200 ml of water. Titrating the C1- 20.00ml of a solution of AgNO3 were required. a) What is the molarity (M) of the AgNO3 solution ? (1 p) (0.100 M)

b) What is the pAg value at the equivalence point? (i p)

Answ. : pAg = 5

c) Represent graphically the changes: A) of Ag + in solution (1 p)

B) the changes of the weight of precipitate during this titration (1 p)

8 7- 6 - 5- 4- 3- 2- 1-

pAg

-5 I

ll0 20 ml Ag NO 3

m- motes of AgC[

2-

10 20

m[AgNO 3

VI/23. The following data were obtained from the polarographic Tt determination in EDTA solution:

59.6%

58.4%

= 9 . 0 %

B = 12.4%

Potential (V): 0.50 0.65 0.70 0.75 0.80 0.90 1.00

Current (pA): 0 1 7 27 41 45 45

Calculate :

a) The limiting current, i a (1 p.). Answ. : 45 gA b) The half-wave potential, E1~2 (1 p.) Answ. : 0.74V

VI/24. The height of the polarographic wave of saturated PbBr2 was 26 ram. Under the same conditions 0.01 M Pb 2 + gave 20 mm for the height of wave. a) What is the concentration of Pb 2 § in saturated PbBr 2? (2p) Answ. : (Pb z+) = 1.3 x 10 -2M b) Calculate the solubility product of PbBr2 (2 p) Answ. : SPpbm2 = 8.8 x 10 -6

9.0% 5.6%

67.4 %

42.7%

V. Vajgand: International Student Competit ions

Table 3. (continued)

VII/23. A well-known chemical process in industry following graph: is presented by the

cool I B .air "~" t ""'""'" ..... ...........

".. / '.., \ C+D d ~... .,,." -.,..\ ", , . . . / NaCL ""., . / "..}\ " - . / C.xH 20 _ _ ~ _ _ �9 - \

chimhey I~, B ~ " F i gases -.} /

%0 j . "..', pD . . . . . . . ,,E /

a i r ................ . , - . . . . i . : ' :11.. . . . . ~, , , ........... ' :~ - . . - . - . . ~ ............... o i r

H2S

b) Write chemical equations of reactions used in the volumetric determination of the final products, A and C, of the mentioned process !

For A: HC1 + N a O H -* NaC1 + H20

For C: Na2CO 3 + 2HC1 -~ 2NaCI + CO2 + H20

a) Put chemical formulas in place of the letters :

A = (HC1) B = (CaCO3) C = (NazCO3) D = (CaS) E = (SO3) F = (H2804)

VII/24. The scheme of a gas analyzer for automatic recording of 0 . 0 1 - 2 ~ SO2 in chimny gases is represented in the picture. The conditions of the process were : Flow rate of gases : 1 0 0 - 300 ml/min Electrolyte: 2 - 5 ~ H2SO 4 -I 1 ~o CuSO4 q - 9 4 - 9 7 ~ H20 with a flow-rate of 0.1 ml/min. Potential drop between D and E: 1.00 V (constant) I = Cu electrode H = graphite electrode

A

I

1

B

a) Write chemical equations for the electrode processes taking place during the determination:

1.

2.

b) Which letter in the scheme indicates the places where the recorder should be put to follow automatically changes of SO2?

(G)

c) Which of the electrochemical quantities - Ec, Ea, i, 2 - is recorded in order to'follow the changes in SO2?

275

Percentage of correct answers :

l%

1%

(i) 1 7o

276 Fresenius Z. Anal. Chem., Band 297 (1979)

Items were classified in five main groups, labeled by A, B, C, D and E in Table 2. From this table the following conclusions can be derived:

Group A contained on average the easiest items: qualitative analysis (which requires observations and memory, without engaging higher mental abilities), balancing chemical equations (requires knowledge of oxidation numbers and skill in manipulation with them), stoichiometry, applied also to gravimetric and gas analysis. This group uses concepts learned mainly in secondary school and applied on a higher level at university.

Group B consisted of problems concerning equilib- rium. Competitors achieved almost the same per- centage in problems dealing with pH and solubility, but lower percentage was achieved when equilibrium con- stant calculation or concentrations from equilibrium constants were demanded. The most difficult problems for the competitors were connected with complexes (only 14.6 ~o positive answers as an average from 23 items, while 3 items were not solved by any com- petitor).

Group C consisted of problems dealing with calcu- lation of concentration of solutions when prepared (the easiest of all topics), various calculations in volumetric analysis and potentiometry (linked with redoxpro- cesses). The average in group C was 27 ~ positive answers, just the same as the average of all topics.

Group D could be called "instrumental methods (without potentiometry)". Competitors were best in optical methods, but showed unsatisfactory knowledge in chemical kinetics, thermochemistry, electrical and physical methods.

The worst results were obtained in group E, divided in two sub groups: statistics (13 items, 2 4 ~ positive answers) and graphical presentation (43 items, 16.6 positive answers). Characteristic of this group is a much higher relative average deviation than in any of the other topics (79 ~). High relative average deviation (proportional to the variation coefficient) points to great differences in knowledge in the given topic.

The most interesting findings were obtained in the subgroup of graphical presentation. We have already mentioned that competitors had easily solved problems involving qualitative analysis, when they were for- mulated in the usual way learned in the curriculum. But when they were presented graphically, as can be seen in problems VI/I and VII/23 (Table 3), the percentage of positive answers dropped to very low figures! Obviously, the graphical presentation was unusual for most of the competitors. This can be confirmed also in potentiometry (comparing the percentage of positive answers in items VI/14, a and b against c), or in polarography (problem VI/24 vs. VI/23, Table 3). The inability of graphical presentation, even when the

2 . 0 -

1.5-

1.0-

0.5-

0.0

-0.5-

-1.0-

-1.5-

igrel,Hg / ' / "~QN

\ \

\ \

Eobs, Ng

given

~--------Q Eobs,Co

/ 11

- 2 . 0 - I I I I ~ I

1973 197/,. 1975 1976 1977 1978

Fig. 2. Average errors in determination of Ca and Mg

problem requires it, is a serious hindrance in the knowledge of competitors.

Another point, that should be also mentioned, is the absence of the ability to apply known principles to practical problems, for example to environmental ana- lysis. The figure in problem VII/24 (Table 3) depicts one of such problems, concerned with the continuous, automatic following of SO2 in chimney gases by the polarographic method. Only a ~ of the competitors was able to recognize in the given scheme that current should be measured in the continual process and that the letter G labels the place where the recorder should be connected in order to monitor the process.

All these weak points in the knowledge and abilities of the competitors reflect the defects in our teaching methods, used in Analytical Chemistry. Graphical presentation and problem-solving should be used much more in education of the future analyst. We should not only teach them theoretical concepts and give them a lot of observations during practical work, but also extend the use of analytical to real, vital life-problems.

Determination of Ca, ranging from 12-22 mg and of Mg from 8 -15 rag in 20ml was the task of competitors in the practical part. In the diagram (Fig. 2) the average errors made by the competitors each year are shown vs. the given amounts of Ca and Mg. A considerable improvement was achieved, both in di- minishing absolute as well as relative error. Although a systematic negative error still exists due to the copreci- pitation of C a 2 + on Mg(OH)2, competitors success- fully diminished coprecipitation of Ca 2 + by previous complexation.

V. Vajgand: International Student Competitions 277

Conclusion

International Student Competitions in Analytical Chemistry are useful and of great value in many aspects:

- t h e y represent novelty in teaching at the uni- versity level,

- they offer possibilities for evaluation of knowl- edge, speed and psychologicsl stability of competitors and show their skills in practical work,

- they serve as a new form of international cooper- ation in education of most talented students.

References

1. Eysenck, H. J.: Brit. J. Educat. Psychol. 37, 81-98 (1976) 2. Vajgand, V.: International Student Competitions in Analytical

Chemistry, Paper distributed at the Special Session in Education in Analytical Chemistry at Euroanalysis III, p. 9-10.

Received December 19, 1978