The Significance of Thermal Analysis in the Development of Teaching Materials for Chemistry Education

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1 Netsu Sokutei The Significance of Thermal Analysis in the Development of Teaching Materials for Chemistry Education - As Exemplified by the Precipitation Reactions of Zinc Salts and their Thermal Decompositions - Haruhiko Tanaka, Yoshinobu Matsuda, Nobuyoshi Koga, and Yoshihiro Furukawa (Received May 10, 2004; Accepted June 24, 2004) Thermoanalytical studies of reactions involving basic zinc salts were made as an example of application of thermal analysis to the fundamental research on developing teaching materials for chemistry education. The studies were complemented by ph titrimetry, thermometric titrimetry, chemical analysis, IR spectrometry, and X-ray diffractometry. On the basis of the results, the possibility was suggested that some investigative teaching materials are developed by introducing the precipitation reactions and thermal decomposition of the basic zinc salts into chemistry courses at a secondary education level. It was proposed that the thermoanalytical measurements for the basic zinc salts applied in the present study are also utilized successfully as teaching materials for educating thermal analysis at universities and colleges. 1) * p.136. III II Fe 3O 4 X TG Fe 2O 3 Fe 3O 4 Fe 2O 3 2) 2004 The Japan Society of Calorimetry and Thermal Analysis. 108

2 3) 4-7) II 8-12) II II 13) II II 14,15) II II 16-24) II TG 25-28) Table 1 Reactions for the precipitation from solutions. Reaction Zinc salt Titrant solution t / Titration speed solution / ml min 1 I 0.1M-ZnSO 4 0.2M-NaOH II 0.1M-Zn(NO 3) 2 0.2M-NaOH III 0.1M-ZnSO 4 0.1M-Na 2CO IV 0.1M-Zn(NO 3) 2 0.1M-Na 2CO *1M 1 mol l 1. Table 1 I IV 100 ml ph ph I 0.5M- ZnSO 4 20 ml 1M-NaOH 0.36 ml 29) 30) 0.1M-ZnCl ml 0.2M-NaOH 500 ml 6M-NH 3 X XRD IRTG-DTA XOedta Zn 2 XRD RINT-2200 Cu-K α, 40 kv, 109

3 ph ph n(oh ) / n(zn 2 ) n(co 3 2 ) / n(zn 2 ) Fig.1 Typical ph titration curves for Reactions I and II, together with a thermometric titration curve for Reaction I. Fig.2 Typical ph titration curves for Reactions III and IV. 20 ma Shimadzu FT-IR8100 KBr IR 10 mg 10 TG-DTA III IV IIJIMA LX-720 NTK HT20 TG-DTA TG-DTA- EGA Fig.1ZnSO 4 Zn(NO 3) 2 NaOH I II ph ZnSO 4 NaOH I OH /Zn Zn 2 :OH 2:3 Fig.1 Zn(NO 3) 2 NaOH II OH /Zn ZnSO 4 Zn(NO 3) 2 ph Fig.2 ZnSO 4 Zn(NO 3) 2 Na 2CO 3 III IV ph III IV ph CO 2 3 /Zn Na 2CO 3 Table 2 ph I Zn 2 :SO 2 4 4:1 Zn 4(OH) 6SO 4 4H 2O II Na 2CO 3 III IV ZnSO 4 Zn 2 Zn 2 ph Zn 5(CO 3) 2(OH) 6 Zn 4CO 3(OH) 6 H 2O Zn 2 III IV [Zn(NH 3) 4] 2 Zn 2 Zn(OH) 2 Fig.3 IR I cm 1 SO 2 4 Fig.3(a) 3303 cm 1 O-H OH 1633 cm 1 H-O-H 110

4 Table 2 Chemical analysis of the precipitates yielded according to Reactions I IV and from [Zn(NH 3) 4] 2 solution, together with calculated values for the typical zinc salts. Precipitate or typical zinc salt Content / wt % Zn 2 SO 2 4 NO 3 precipitate yielded according to Reaction I precipitate yielded according to Reaction II Not detected precipitate yielded according to Reaction III precipitate yielded according to Reaction IV Not detected precipitate yielded from [Zn(NH 3) 4] 2 solution Zn(OH) 2 (FW 99.40) 65.8* Zn 4(OH) 6SO 4 4H 2O (FW ) 49.2* 18.1* ZnCO 3 (FW ) 52.2* Zn 5(CO 3) 2(OH) 6 (FW ) 59.6* Zn 4CO 3 (OH) 6 H 2O (FW ) 59.2* * Calculated values. Transmittance Intensity (a.u.) Fig.3 ν ~ / cm 1 Typical FTIR spectra for the precipitates. 2θ (Cu-K α) / deg II IR cm 1 ν 3 31) Fig.3(b)[Zn(NH 3) 4] 2 Fig.3(c) Na 2CO 3 III IV IR Fig.3(d) IR II 3318 cm 1 O-H IR III IV Fig.4 Typical XRD patterns for the precipitates. Fig.4 XRD I XRD Fig.4(a) Zn 4(OH) 6SO 4 4H 2O JCPDS ph Zn 2 SO 2 4 II XRD Zn(OH) 2 JCPDS Zn 5(CO 3) 2(OH) 6 JCPDS Zn 4CO 3(OH) 6 H 2O JCPDS ZnO JCPDS

5 ( m / m0) / % T(emf) / µv Exo. ( m / m0) / % T(emf) / µv Exo. Fig.5 Typical TG-DTA curves for the thermal decomposition of Zn(OH) 2. Fig.4(b) XRD ph [Zn(NH 3) 4] 2 XRD Fig.4(c) Zn(OH) 2 JCPDS Na 2CO 3 III IV XRD Fig.4(d) XRD Zn 5(CO 3) 2(OH) 6 JCPDS Zn 4CO 3(OH) 6 H 2O JCPDS ) ZnSO 4 NaOH I 4ZnSO 4 6NaOH 4H 2O Zn 4(OH) 6SO 4 4H 2O 3Na 2SO 4 (1) [Zn(NH 3) 4] 2 [Zn(NH 3) 4] 2 2OH Zn(OH) 2 4NH 3 (2) Zn(NO 3) 2NaOH II ph Na 2CO 3 III IV ph Zn 2 XRD Fig.6 Typical TG-DTA curves for the thermal decomposition of the precipitate yielded according to Reaction I, Zn 4(OH) 6SO 4 nh 2O. Fig.5 [Zn(NH 3) 4] 2 Zn(OH) 2 TG-DTA % 18.1 % Zn(OH) 2 ZnO H 2O (3) I TG-DTA Fig.6 IICu 4(OH) 6SO 4 nh 2O 11.5 % 13.5 % 3.4 H 2O SO 3 H 2O/SO 3 3 ZnO Zn 4(OH) 6SO 4 nh 2O Zn 4(OH) 6SO 4 nh 2O (n 4 3) (4) Zn 4(OH) 6SO 4 Zn 4O 3SO 4 3H 2O (5) 112

6 ( m / m0) / % Fig.7 T(emf) / µv Exo. Typical TG-DTA curves for the thermal decomposition of the precipitate yielded according to Reaction II. ( m / m0) / % Concentration / g m 3 T(emf) / µv Exo. Zn 4O 3SO 4 4ZnO SO 3 (6) Zn(NO 3) 2NaOH IIFig.7 TG-DTA Fig.5 Zn(OH) 2 Fig.8III IV TG-DTA-EGA H 2O, CO 2 TG-DTA TG 258 DTA 27.6 % Zn 4CO 3(OH) 6 H 2O 26.3 % 25.8 % Zn 5(CO 3) 2(OH) % TG EGA Fig.8 Fig.8 Typical TG-DTA-EGA (H 2O, CO 2) curves for the thermal decomposition of the precipitate yielded according to Reactions III and IV, Zn 5(CO 3) 2(OH) 6 nh 2O. H 2O/CO III IV Zn 5(CO 3) 2(OH) 6 nh 2O Zn 5(CO 3) 2(OH) 6Na 2CO 3 33) 5Zn 2 5CO 2 3 3H 2O Zn 5(CO 3) 2(OH) 6 3CO 2 (7) Zn 5(CO 3) 2(OH) 6 nh 2O Zn 5(CO 3) 2(OH) 6 nh 2O (8) Zn 5(CO 3) 2(OH) 6 5ZnO 2CO 2 3H 2O (9) III IV 80 Fig.9 113

7 Fig.9 A diagram of the precipitation and thermal decomposition reactions of zinc salts. 34,35) ZnSO 4 NaOH I II 27) ph Zn 2 SO 2 4 Na 2CO 3 III IV ph Zn 2 CO 2 3 ph Zn 2 ph Zn 2 Zn 2 ZnO 7) ZnO Zn 2 CO 2 3 Zn 5(CO 3) 2(OH) 6 TG TG-DTA II 1) 114

8 TG IR XRD II 27) TG 26) 25,28) ph TG IR XRD Zn 4(OH) 6SO 4 nh 2O Zn 4(OH) 6SO 4 nh 2O Zn 5(CO 3) 2(OH) 6 Zn(OH) 2 TG DTA Zn 5(CO 3) 2(OH) 6 TG IRXRD Fig.8 EGA EGA EGA C B C ),, (1998). 2),,, 43, 260 (1995). 3), 15, 18 (1967). 4) L. C. King and M. J. Cooper, J. Chem. Educ. 42, 464 (1965). 5),,,, 20, 232 (1972). 6), 23, 71 (1972). 7) S. DeMeo, J. Chem. Educ. 81, 119 (2004). 8) H. Tanaka and N. Koga, Thermochim. Acta 133, 221 (1988). 9) H. Tanaka, M. Kawano, and N. Koga, Thermochim. Acta 182, 281 (1991). 10) H. Tanaka and S. Terada, J. Thermal Anal. 39, 1011 (1993). 115

9 11) H. Tanaka and M. Yamane, J. Thermal Anal. 38, 627 (1992). 12) N. Koga, J. M. Criado, and H. Tanaka, Thermochim. Acta 340/341, 387 (1999). 13),, 36, 300 (1988). 14),, (1995). 15),,,,,, 49, 726 (2001). 16) W. W. Wendtlandt, J. Chem. Educ. 38, 566 (1961). 17) R. S. Botti and P. L. Grace, J. Chem. Educ. 38, 568 (1961). 18) E. G. Malawer and E. R. Allen, J. Chem. Educ. 54, 582 (1977). 19),,, 29, 139 (1981). 20),, 31, 38 (1983). 21) E. Wiederholt, J. Chem. Educ. 60, 431 (1983). 22), 32, 246 (1984). 23) A. M. Wynne, J. Chem. Educ. 64, 180 (1987). 24) J. O. Hill and R. J. Magee, J. Chem. Educ. 65, 1024 (1988). 25),,,, (1988). 26),, 37, 310 (1989). 27) H. Tanaka and N. Koga, J. Chem. Educ. 67, 612 (1990). 28) H. Tanaka, N. Koga, and A. K. Galwey, J. Chem. Educ. 72, 251 (1995). 29),,,, II 20, 79(1998). 30) W. A. Herrmann (ed.), Synthetic methods of organometallic and inorganic chemistry, Vol.5, Georg Thieme Verlag, Stuttgart, p.123 (1999). 31) D. Stoilova, V. Koleva, and V. Vassileva, Spectrochim. Acta, Part A 58, 2051 (2002). 32) K. Kanari, D. Mishra, I. Gaballah, and B. Dupre, Thermochim. Acta 410, 93 (2004). 33) S. C. Zhang and X. G. Li, Colloids and Surfaces A 226, 35 (2003). 34),,, 52, 116 (2004). 35),,, 10, 11 (2004). Haruhiko Tanaka, Graduate School of Education, Hiroshima Univ., TEL. & FAX , htnk@hiroshima-u.ac.jp Yoshinobu Matsuda, Graduate School of Education, Hiroshima Univ., TEL. & FAX , ymatsuda@hiroshimau.ac.jp Nobuyoshi Koga, Graduate School of Education, Hiroshima Univ., TEL. & FAX , nkoga@hiroshima-u.ac.jp JUDO Yoshihiro Furukawa, Graduate School of Education, Hiroshima Univ., TEL.&FAX , yfuruka@hiroshima-u.ac.jp 116

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