Modification of the Experimental Setup to reduce Misconceptions for the Voltaic Cell described in High School Chemistry Textbooks

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1 Journal of the Korean Chemical Society 2003, Vol. 47, No. 1 Printed in the Republic of Korea * ( ) Modification of the Experimental Setup to reduce Misconceptions for the Voltaic Cell described in High School Chemistry Textbooks Nak Han Jang, Kyung Ok Lee, Jin Seung Lee, and Jung Sang Suh* School of Chemistry and Molecular Engineering, Seoul National University, Seoul , Korea Department of Chemistry Education, Seoul National University, Seoul , Korea Eonnam High School, Seoul , Korea (Received December 17, 2002). II!" #$%&'()*. +,-. " / ! *: ;" < #$ =>*. & B. C 1.1 VD EF(2 GH. IJ KL(: MN OM. P*. QR ST U V.V 9W : *XY Z[ 1.1 V\ 89 0*. & - ] ^5_` ab" cd ef " / 012.; - g9d *h i / jk k* elm*. pq. *XY pd r5 EF( st. uv(e " /m*. wo, & ab- QR ST/ xy z{ 8d} 89 01~\. ab" (Jd QR ST Uq" " P st ef " / *. IJ 5 : " ƒ 0: ab " ˆ ()*. :,, ab ABSTRACT. Misconceptions of students for a Voltaic cell were studied and their contents described in the high school chemistry II textbooks were analyzed. This study shows that students have many misconceptions and a few of chemistry textbooks contain some false description in a Voltaic cell. In the most textbooks, the reasons why the measured cell voltage of a Voltaic cell is near 1.1 V at the initial stage and then it decreases with time are not explained clearly. The emf of a Voltaic cell at a standard state is 0.76 V but in some textbooks it is described as 1.1 V of a Daniel cell. Even after learning the Voltaic cell or performing the experiment of textbooks, most students still have some misconceptions. These may be due to at least two following facts: the first is that the measured cell voltage of a Voltaic cell at the initial stage is very similar to that of a Daniel cell. The second is that the most experiment of a Voltaic cell is not performed under the condition of a standard state. Therefore, we have suggested a model of the modified experimental setup of a Voltaic cell that could reduce misconceptions of students. Key words: Voltaic Cell, Misconception, Modified Experimental Setup 79

2 80 ˆ6%7Š A II! : Œ% Ž. 89 0*. - D U(emf) ".+(: ;" 9 (2, aˆ\,- " / 0* Œ% &' #$. 9: k š Ot - 37%D 36% V. œ ž " / 0* ()*. Garnett Treagust #$ 2-3 (Ÿ Œ -, L...v (e " /m* ()*. -.v.` U Œ " /2,. - ` 67 * ()* OgudeD Bradley #$ 6 :. š. ` F 67 OM k 012 ss \ S 67.+\ª * OM()*..+] «p+ ] 1 0:. r5 j(*. 7 #$. ].+(:,- 9 " ± 0* ()12, IJ Œ% Ž &1\ D *XY ].! (e D U " ²( : ;. ³j(*. f, : ] OM( / ±: U q".µg1\ $ 0: U" 5: r5 j " *. ¹º` š,- ` " 1 0:!. 0.]»( &'(: ;. r5 j( J *. < #$: Ž U š " œ ¼.+ 0: U" ½SG¾ " AG g1\ š &' ab ÀÁ] ˆ ()*. < #$ $Âgk!- *h Ã*. ÄÅ " zf(. k (`k ] &'()*. $ / Æx Ž Çe*: " ( p(e QR ST z{" V9 ab sè* ÉJ: ¹.E] OM( QR ST U. AN( ÊÈk] Ëx ()*. aì ab ÀÁ $ÍS gîí" ( e Ïd QR ST.µg U Ð (: abq" " 0d} L Ñ ÀÁ].! (: ab " ˆ ()*. Ot zf: G 45M" S1\ (e ab %c i ŠÒ ÓÔ a ()*. a b- } 1\ + a 8 Õ12 ab- #$ + aba a 8Õ*. ˆ6Š A II 10Ö ŒD ˆ7Š A 8 II 5Ö Œ% &" 9 &'()*. \!, U Ø EÙ] &'()*.. #$ F! Ö : gk ÚÛ (e & 8Õ*. " S1\ QR p].!(e QR ST U" Œ(: ; Ot Ü] Table 1 QG()*.. Ü (Ÿ i U" 0.76 V : 1.10 V\ Ý(), V Þ V \ Ý - ß PÕ*..;- Ot Ý à - (-) x# Œ Ž. 9`, Table 1. Types of question and answer. It was questioned before doing the experiment of a Voltaic cell Question Percent of answers Calcualte the theoretical cell voltage in a voltaic cell at a standard state (25 o C, 1 atm). half-reaction Zn 2+ +2e Zn(s) Cu e Cu(s) 2H + + 2e H2(g) E o (V) V : 96% 0.76 V : 4% Journal of the Korean Chemical Society

3 (+) L` $ Ž. 9á*: ;1 \ ( U" $* âa 0*. ¹º`, 4% V VJ œ ž Ý" ;1\ x zf S &k 96% : p] Œ s: (+) $. Ž. 9á* ( U" 1.1 V\ Œ* âa 0*. ã. U" 1.1 V\ Œ(: ;- *XY Ž " D uv(e U Œ $ / * 67.+( 0* *. I J 5 : e. C D *XY ] uv(: " / 8:] zf+ p+ ÄÅ. ^5:!" &'+ ä*. µ ] " EÑ(: 4g jk (`\ å] Õ*. IJ, æ F!( 0: 6 Š II D ç1\ F!è 7Š II š &' " ƒ 0:!" éx &'(e Table 2 ˆG ()*. U. ê 1.1 VJ: ë:. æ F!( 0: ˆ6Š A II zf 10Ö 7Ö 81!" *ì 0Õ12, 6Ö / Ú s 9`: ] Ž í " F!(e OM( 0*. ¹º`,. 10Ö 4Ö : ÚG pš] 1.1 V\ 6 7 ( 012,.Ã. ; Qgk å: *h Ã*. 1.1 V... (6-G) 1.1 V (6-E). f 6-E : *XY " ˆG( J (: 67" e ë 0*. ˆ7Š A F! 5Ö 3Ö. e f š(e Ø()12, ¹ d xîd Ã-!. 8Õ*.!" #!$ 1.1 V % &... (7-C).D Ã. ˆ7Š d ˆ6Š Èï /\ ê 1.1 V / ` * (e QR ST U. 1.1 V J: " ë 8: jk Table 2. Analysis of a Voltaic cell in the high school chemisry II textbooks based on the 6th and 7th educational curricula ( : mentioned, : not mentioned, -: not published) Textbook 6th 7th Content Model emf (V) Content Model emf (V) Misconceptions 6-A mentioned the Daniel cell voltage instead of 0.76 V. 6-B No 6-C No 6-D mentioned the Daniel cell voltage instead of 0.76 V. 6-E Daniel cell model regarded as a Voltaic cell model and mentioned the Daniel cell voltage instead of 0.76 V. 6-F G mentioned the Daniel cell voltage instead of 0.76 V. 6-H 7-A No 6-I 7-B 6-J 7-C V mentioned the Daniel cell voltage instead of 0.76 V. 7-D No 7-E , Vol. 47, No. 1

4 82 1\ $Í89 0 ÚG D *XY (+) - i ] òxe Ž. 9á*. ¹º` (+) Ž ó Çe(: ôõ- $ / xx L..2, ] òx L Â\ öd $( - *XY 45Z[ $.. $ \ 8: ;1\ ( U Œ 1.1 V\ " /m* *. IJ ] OM s ab" + ".+G _`, *XY V1\ OM(: ;. " ƒ 0* *. 10 ¹º`, ˆ6Š A 4Ö ˆ7Š A 1Ö / D *XY å] ø 9 QR ST U OM" ( 0*.. U" $(: \ ù ú" F!(: QR L *ž QR p] $(: ÚÛ + ( 0*. QR L å: xîd Ã*. Fig. 1. Experimetal setup model of (a) a Voltaic cell, and (b) a Daniel cell in high school chemistry II texbooks.. 82.: #$ ÜD Á* * ˆ6%7Š 6Ö 3Ö. Fig. 1 Ã- (a)d *XY (b)] i.!(e ] OM( 012, å : xîd Ã*. '...().. (-)* +, -./ 0, (+)* + 1-2/ 3....()... (-)* -./ : Zn 4 Zn e (56) (+)* 2/: 2H + + 2e 4 H 2(78)...()... 9:...()... (-)* -./ : Zn 4 Zn e (56) (+)* 2/ : Cu 2+ +2e 4 Cu(78) p ð. i (+) - i $ ñ ;< => *...()... 1 MA BC D EF/ G0, EF/ 1 H 2 H IJK0 L M N O L. P, H + (aq) Q H 2 (g) RS RT UV W(E o ) 0.00 V!X. 2H + (aq, 1M) + 2e H 2 (g, 1 atm) E o =0.00 V pd Ã. ˆ6Š ûv xxj 7Š II : QR L p <gk!v" ( 09 (+) Ž. QR L Ž Ã- Ž.~\ QR ST (+) p/ 0 VJ: ;".+(: r5 9 ü*. ¹º~\ U" OM s (+) : $ / Ž Çe(: ;. xxj L.. L Â\ 8: Ž. 9` st QR ST Žý Ž p: 0 VJ: ;" þz+ÿ V. U.+] s " ƒ 0* *. Fig. 1(a) 0: ab " F!(e ab" ( ()*. - $ ñ sv / 5? v Bq" }()*. ab" c Ot" (e Journal of the Korean Chemical Society

5 Table 3. Types of question and answer. It was questioned after doing the experiment of a Voltaic cell described in textbooks Question Percent of answers Q1. What is the obseved cell voltage? Q2. What is the theoretical cell voltage in a voltaic cell at a standard state (25 o C, 1 atm). Q3. Explain the reason why the measured cell voltage is different from the theoretical one. ¹ Ü] Table 3 QG()*. Ot 1 (Ÿ à. š Bq- Zh 5? v / 0V 0.90 V.( \ / ä*. 15% - ab Bq. /: ;" B" 0.90 VJ Ý1` 35% - Bq. q1\ Ý()*. ¹ *k 50% - Hqk 0.93 VJ Ý()*.. ab Ü: p abq. Âg1\ r VD EF(* 0*. Ot 2 Ü (Ÿ ab" cd _ &k 95% - ef.µgk U Vk ;1\ kí( 0 h" e ëõ*. IJ. Ü:. ab" (Jd ¹ p - ef 1.10 V\ ( 012 ab ab pq.. * x: ;- & S st.j " /õ 0h" eë 0*. aˆ \ Ot 3,- - L Â/ Ñ(: ;" š( s ÉJ :.E\ & S st.j ( 0*. ¹ L - d` d Š., QŸ.ôõ (_` B / AN( 7( s t.j Ý()*..;- U- QŸ -.ôõ + ÉJ2, & S- Ú ( È ``: ;1\. kí( 0*: ;1\ +'*. Žg1\ f 0: 2003, Vol. 47, No. 1 Over 0.97 V: 35% 0.93 V: 50% 0.90 V: 15% 1.10 V: 95% 0.76 V: 5% Hydrogen polarization: 75% Solution concentration gradient : 10% Temperature difference: 6% Instrument error: 6% Air bubble: 3% 83 ab - $ ñ x#ñ" Œ! ¹ 82. s $ QŸ x# QŸ 9W Â / Ñ(: š( *. ú. 4½. L * ú- Œ! Ž (e L Â ] ÑG*. - $ / Œ! A ú d $( f L/ Ñ(~\ $ / $. 1\ 8Ÿ L] ÑG* (_` : *XY D u v(e $.. $ / * (: * âa 0*. ¹º~\ a b $ : ú. 4½ L Â *. 4½. - ý pá(~\ Œ! L Â] ÑG P*: ;" ëg : ;. " ƒ.: d. 8 J *. ab " 0: Bq -? 1.02 V ª 0.90 V (:. S- p/! æ(: Ö d, Ž Çe(: Â &BU, ¹ Ž. 9`: d ( st.*. Ž : Hg1\ d/ m & - &. 0 " 0 Ž Çe(: L &B. A( " Bq- &B IJ ÉJ *.» Œ! pý QŸ- ŒLDd ( 01~\ B" s Ú» ST: L &B. x Ž ½" ë è ;1\ *. IJ. ab" (Jd eº / jk st AN pq" " P9 +Ü d " 7* *. ¹º~\ " ƒ.: d. 8d} AN pq" " 0: \ ab. j$* *. U ab p ½" ƒ 0: eº jk + Agk &'" ()*. 25 o C Nernst ÚAí".!(Ÿ UxîD Ã. Q 82,. ÚAí- d IJ U. 9 ``: ] er*. 11 : 2H + (1M)+2e H 2(g, 1 atm) E o H + /H2= 0.00V Œ : Zn(s)Zn 2+ (1M)+2e E o Zn 2+ /Zn= 0.76V Zn(s)+2H + (1M)Zn 2+ (1M)+H2(g, 1 atm)

6 84 Table 4. Experimental results measured by using a Voltaic cell at 25 o C, 1 atm hydrogen pressure Experimental condition Solution concentration Observed emf (V) Theoretical emf (V) 1 M H2SO (A) Different concentration of H2SO4 0.1 M H2SO M H 2SO M H 2SO M ZnSO (B) Same concentration of H 2SO 4 but different concentration of ZnSO 4 1 M H 2SO M ZnSO M H 2SO M ZnSO (C) Different concentration of H 2SO 4 but same concentration of ZnSO 4 1 M H 2SO M ZnSO M H 2SO M ZnSO M H 2SO M ZnSO E= E o [ a 2+ ] [ a Zn H2 ] log [ ] [ a + ] 2 H a Zn [ E = log Zn2+ ] P H (1) 2 [ 1] [ H + ] 2 í (1) ð. U E: x#. d [Zn 2+ ], L. d [H + ], L &B P H 2 *. E/ [Zn ]D 2+ [H ] 9 Ad + (: ] Ë p(e L!] F!(e L BU" 1B" E(! eº d z{ ab" (e Table 4D Ã- Ü] Õ*. z{(a) Ü: H2SO4] +õ\ (e d] É (Ÿ H 2SO 4 d/ "} U q- x: 4 ½".2,.;- í (1) eë: 4½Í Á*. z{(b): H 2SO 4 d] 1M\ E( ZnSO 4 d/ 1 M, 0.1 M, 0.01 M s ;.*. ZnSO4 d/ 1 M, 0.1 M _ Á( ` 0.01 M 45:.µq * 0.03 V *. z{ (C) ZnSO4 d] 1 M\ E( H2SO4 d] 1M, 0.1M, 0.01M\ G Ÿ _ Á*. I J L Â &B" 1B1\ E(: 45 L. d [H ]D x#. d + [Zn ]: U 2+ ½" ë : ;" 0*. ã í (1) L. d [H + ], L Â &B PH 2 D x#. d [Zn ] : i Uq 2+ ½" ƒ 01` aˆ (-) Ž Í x#. -! 8~\! 1\ Éx`: L Â &B PH 2.! U ½" ƒ ;.*. ab L Â &B. 1atm s 25 o C, 1 M H 2SO 4+1 M ZnSO 4!.µq- xîd Ã. Q * E = log [ 1] [ 1] = 0.76 V 2 [ 1] [ 1] 2 Œ x#. d/ 1Mk! $ D x# " ¹ Ü? abq í (1)\ ª E = log [ 1] P H = 0.99 V 2 [ 1] [ 1] aˆ! L Â &B- ê atm1\ Œ82 t"s `á L 12 Â &B atm.~\ 9 Ad # 0* âa 0*. L Â\ (50&.S) Œ! B V \ $9: ;. š8õ*. QR ST GH. 48Ÿ B. $92.;- & S st.j OM( 0*. &. 9`Ÿ L / $ ñ ëp 89 É À% " ( 8 9 B- $9 *. f & 9 `: D '( kíû xxj QR ab z{".+g : ;. j(* *. IJ Ñ(: L Â &B" 1B Ã (. d] 1 M\ (e s.µqk 0.76 VD EF q. 9)" 1\*. " ƒ 0* *. L Â &B" 1B Journal of the Korean Chemical Society

7 Fig. 2. Modified experimental setup model of a Voltaic cell. Ã V p+ F!( pb L! + H ab ÀÁ\, L] ÑG ¾ $ Ð L Â &B" 1B»-( V 0:./ $ (+) " VÕ*. " ƒ 0: ab " Fig. 2 ˆG()*. 0 ab z{- *h Ã*. ] / ÉÌ 1 2J3! #Ü( 45 F.: 67" (e L / 898 d} *. 500 ml / ÉÌ 1 2J3! ý: L/,. Ñ8 d} :& & x# z (ê 30 g Ad)" ; 7M <Œ( : 8M <Œ)" =s] ml~450 ml Ad ;:*.. s ë+ÿ F>- <Œ!"??f Ú ÿ (2 A3B,- Ÿ L Â BU + Œ!.» 1\ CÔ ` *. / ÉÌ 1 2J3! # g1\ L / Ñ(2. L Â: 45] +» 0: $ Œ 85!- L Â\ ST/ *. 3D Á] R»(e R GH" Ë 0 *. ê 20 & v E c L &B. B F. 8: ;1\ Hë( sv x#ñ " ¹d} *. x#ñ" /iÿ? Bq. êh (` 1& 0.76 Vq dé*.. ab :!` & Iž B SšÍ" Ë x p+ úñ!] *¼ (2 ()*. ab Ü U V Ð( 8: $ ñ z{- $ ñ" G.] ê 10 cm Ad \ ( H &" AF k 0.5~0.8 cm!\ /I V9 F!(: ;. J*: ;" Ëä*. L Â/ \ Í8: K AF $ ñ - +õ LŽ Ad Md} *. x#ñ- N. 0.5 cm, G. 10 cm!] F!(: ;. Jä*. p Ã- ab 1\ eº /! d ab" Bq..µqk 0.76 V Ð(: ;" Nk 0*(Table 5).. ab Ü: L Â &B" 1 B1\ AG ab Ük Table 4D EF " ` 2, IJ 5 / ˆ ab. L Â &B" (: Og., AN 0 st " ƒ 0* *. QR ST U Œ - ] *XY D uv(e $.. Ž Çe* (: " /: ;1\ `P*.! &',- Table 5. Experimental results measured by using the modified setup of a Voltaic cell Solution concentration Observed voltage (V) Theoretical voltage (V) Experimental temp. ( o C) 1 M H 2SO ~ M H 2SO M H 2SO M H 2SO M ZnSO ~ M H 2SO M ZnSO M H2SO4 + 1 M ZnSO4 0.67~ M H2SO4 + 1 M ZnSO4 0.77~ M H2SO M ZnSO M H2SO M ZnSO4 0.79~ , Vol. 47, No. 1

8 86. U" *XY 1.1 V\ ( 09 / " ë: jk. 8 0h" Nk()*. ¹º`, ab. QR ST 8 0 st *XY D»- ab cd - ˆ_8 - ;1\ `P*. U " g1\ aì abàá gîí" (e Ïd.µg U Ð(: a bq" : ab ÀÁ] ˆ ()*.. d] 1 M\ A( L Ñ ÀÁ] F!(e L Â BU" 1B»-( A (e U- ê 0.76 V/ 89.µq EF " Nk()*. IJ 5 / ˆ ab - QR ST 09 D *X Y Š.].+G 0 st " ƒ 0* *. 1. Im, H. K. Study of Misconceptions Analysis of Students for Oxiadtion/Reduction and Electrochemical Cell. M. Ed. Thesis, Chungnam National University, Garnett, P. J.; Treagust, D. F. J. Res. Sci. Teach. 1992, 29, Garnett, P. J.; Treagust, D. F. J. Res. Sci. Teach. 1992, 29, Sanger, M. J.; Greenbowe, T. J. J. Res. Sci. Teach. 1997, 34, Sanger, M. J.; Greenbowe, T. J. J. Chem. Educ. 1997, 74, Ogude, A. N.; Bradley, J. D. J. Chem. Educ. 1994, 71, Niaz, M. Int. J. Sci. Educ. 2002, 24, Chemisry II textbooks in the 6th educational curriculum; (a) Lee, W. J.; Bang, T. C.; Lee, S. Y. Chemistry II; Koryo Books Publishing: Seoul, Korea, p 397. (b) Oh, J, J.; Kim, J. H.; Park, B. B.; Choi, S. N. Chemistry II; Kyohaksa Publishing: Seoul, Korea, 1997, p 406. (c) Kim, S, J.; Moon, J. D.; Lee, J. M.; Koo, C, H.; Lee, S. J. Chemistry II; Kumsung Publishing: Seoul, Korea, 1997: p 362. (d) Jeong, G. J.; Ryo, J. H.; Lee, D. H. Chemistry II; Donga Books Publishing: Seoul, Korea, 1997: p 365. (e) Park, T. G.; Jeong, G. C.; Kim, W. T. Chemistry II; Bakyoungsa Publishing: Seoul, Korea, 1997: p 410. (f) Park, W. K.; Yoon, S. J. Chemistry II; Jihaksa Publishing: Seoul, Korea, 1997: p 417. (g) Woo, K, W.; Kim, G. J.; Lee, I. G.; Yeo, S. I. Chemistry II; Cheonjae Education Publishing: Seoul, Korea, 1977: p 341. (h) Yeo, S. D.; Yeo, H. J.; Jang, Y. G.; Lee, G, O. Chemistry II; Cheongmoongak Publishing: Seoul, Korea, 1997: p 410. (i) Choi, B. S.; Moon, Y. S.; Shin, J. S.; Kim, D. S.; Hyun, J. O. Chemistry II; Hansam Publishing: Seoul, Korea, 1998: p 377. (j) Song, H. B.; Jeong, Y. S. Chemistry II; Hyungseul Publishing: Seoul, Korea, 1997: p Chemisry II textbooks in the 7th educational curriculum; (a) Suh, J. S.; Huh, S. I.; Kim, C. B.; Park, J. W.; Hah, Y. K.; Im, Y. J. Bae, B. I. Chemistry II; Kumsung Publishing: Seoul, Korea, 2002: p 296. (b) Lee, D. H.; Kim, D. S.; Shim, K. S.; Jeon, S. C.; Lee, J. H.; Shim, J. S.; Suh, I. H.; Noh, K. J. Chemistry II; Daehan Textbooks Publishing: Seoul, Korea, 2002: p 319. (c) Woo, K. W.; Choi, S. N.; Oh, D. H.; Han, E. T.; Kim, B. R.; Kang, B. J. Chemistry II; Joongang Education Development Center Publishing: Seoul, Korea, 2002: p 270. (d) Kim, H. J.; Yoon, K. B.; Lee, J. Y.; Hwang, S. Y.; Lee, B. Y.; Jeon, H. Y. Chemistry II; Cheonjae Education Publishing: Seoul, Korea, 2002: p 296. (e) Yeo, S. D.; Yeo, H. J.; Jang, Y. G.; Lee, G, O.; Cho, C. H.; Park, H. Y.; Yang, D. K.; Lee, C. G. Chemistry II; Cheongmoongak Publishing: Seoul, Korea, 2002: p Shin, T.-H.; Lee, S.-K.; Choi, B.-S. J. Kor. Chem. Soc. 2002, Harris, D. C. Quantitative Chemical Analysis; 5th ed.; Freeman: New York, U.S.A., Oxtoby, D. W.; Gillis, H. P.; Nachtrieb, N. H. Principles of Modern Chemistry; 4th eds.; Saunders College Publishing: New York, U.S.A., Journal of the Korean Chemical Society