산화와환원 1

산화와환원 1

Oxidation Reduction: The Transfer of Electrons Electrons from copper metal are transferred to silver ions. Silver metal is formed, and the solution turns blue from copper(ii) ions formed. 출처 1 Fig. The displacement of Ag + (aq) by Cu(s) (a) A coil of copper wire is suspended in colorless AgNO 3 (aq). (b) After a period to time, a blue color has developed in the solution and a silvery deposit has covered the copper coil. 2

1. 산화환원반응 oxidation-reduction reaction, or redox reaction 한화학종으로부터다른화학종으로전자가이동하는반응 산화 : 어떤화학종이전자를잃었을때 환원 : 어떤화학종이전자를얻었을때 산화반응과환원반응은반드시동시에진행된다. 전자의이동을수반하므로전지와같다. 산화형화합물 : 전자를받는물질 (electron acceptor) 환원형화합물 : 전자를제공하는물질 (electron donor) Ox + ne Red 예 ) Fe 3+ + e Fe 2+ Sn 4+ +2e Sn 2+ 3

1. Oxidation and Reduction Oxidation/reduction reactions, often called Redox reactions, involve the transfer of electrons fr om one reactant to another. A reducing agent (or reductant) is an electron donor. An oxidising agent (or oxidant) is an electron acceptor. Ce 4+ + Fe 2+ Ce 3+ + Fe 3+ in the above reaction, cerium accepts an electron from iron and therefore is the oxidant. Iron is the reductant. Any oxidation or reduction reaction can be split into two half-reactions that can be added to p rovide the original redox reaction. Ce 4+ + e - Ce 3+ (reduction of cerium) Fe 2+ Fe 3+ + e - (oxidation of iron) Remember: Charges on each side of a redox reaction or half-reaction must balance. 4

2. 산화환원과반쪽반응 유리상태의전자는있을수없으므로, 산화형화합물이전자를수용하려면 반드시전자를제공하여야할환원형화합물이있어야한다. 산화형화합물을 Ox 1 으로하고이와반응할환원형화합물을 Red 2 로표시하면, 두화학종사이에전자의이동이일어나다음과같은산화환원반응이성립된다. aox 1 + ne a'red 1 +bred 2 b'ox 2 + ne aox 1 +bred 2 a'red 1 + b'ox 2 5

산화제 ; 높은전극전위 산화환원적정 환원제 ; 낮은전극전위 출처 2 표 13-1 6

출처 3

Redox Reactions OIL Oxidaton Is Loss of electrons. RIG Reduction Is Gain of electrons. Oxidaton and Reduction must occur together. They cannot exist alone. 8

3. 산화환원반응계의예 2Fe 3+ +2e 2Fe 2+ +) Sn 2+ Sn 4+ +2e 2Fe 3+ +Sn 2+ 2Fe 2+ +Sn 4 I 2 +2e 2I - +) S 2 O 3 S 4 O 6 +2e I 2 +2S 2 O 3 2I - +S 4 O 6 2MnO 4- +10e+16H + 2Mn 2+ +8H 2 O +) 5H 2 O 2 5O 2 +10e+10H + 2MnO 4- +5H 2 O 2 +6H + 2Mn 2+ +5O 2 +8H 2 O 9

4. 갈바니전지과전극전위 (electrode potential) 전극전위의절대값은측정할수없다. 다른전극과의차이를측정할수있다. Person C A B Height relative to post (cm) +20 +15-15 10

5. 산화환원성시약 산화성시약 (1) KMnO 4 MnO 4- + 5e + 8H + Mn 2+ + 4H 2 O; E o =1.51V Mn:+7 +2, 1 eq 1/5KMnO 4 (2) I 2 I 2 + 2e 2I - ; E o =0.54V I: 0-1, 1 eq 1/2I 2 (3) K 2 Cr 2 O 7 Cr 2 O 7 +6e+14H + 2Cr 3+ +7H 2 O; E o =1.33V Cr:+6 +3, 1eq 1/6K 2 Cr 2 O 7 (4) 2(NH 4 ) 2 SO 4 Ce(SO 4 ) 2 4H 2 O Ce 4+ + e Ce 3+ ; E o =1.61V Ce: +4 +3, 1 eq 2(NH 4 ) 2 SO 4 Ce(SO 4 ) 2 4H 2 O 11

5. 산화환원성시약 산화성시약 (5) KBrO 3 BrO 3- + 6e + 6H + Br - + 3H 2 O; E o =1.42V Br: +5-1, 1 eq 1/6BrO - 3 (6) KIO 3 IO 3- + 6e + 6H + I - + 3H 2 O; E o =1.09V I: +5-1, 1 eq 1/6KIO 3 IO 3- + 5e + 6H + ½I 2 + 3H 2 O; E o =1.20V I: +5 0, 1eq 1/5KIO 3 IO 3- + 4e + 6H + + Cl - ICl + 3H 2 O; E o =1.23V I: +5 +1, 1 eq 1/4KIO 3 (7) NaNO 2 R-NH 2 + HNO 2 + HCl R-N NCl + 2H 2 O R-NH 2 HNO 2 12

5. 산화환원성시약 환원성시약 (1) Na 2 C 2 O 4 C 2 O 4-2e 2CO 2 ; E o =-0.49V C: +3 +4, 1 eq 1/2Na 2 C 2 O 4 (2) As 2 O 3 As 2 O 3 + 6OH - 2AsO 3 3- + 3H 2 O AsO 3 3- - 2e + 2OH - AsO 4 3- + H 2 O; E o =0.56V As: +3 +5, 1 eq 1/2AsO 3 3-1/4As 2 O 3 (3) Na 2 S 2 O 3 2S 2 O 3-2e S 4 O 6 ; E o =0.13V S: -1 0, 1 eq Na 2 S 2 O 3 (4) TiCl 3 Ti 3+ -e + H 2 O TiO 2+ + 2H + ; E o =0.1V Ti: +3 +4, 1 eq TiCl 3 13

6. 산화제의종류와성질 산화제화학식식량반응 E o (V) 당량수 과망간산칼륨 ( 강산성 ) MnO 4- + 5e + 8H + Mn 2+ + 4H 2 O 1.51 5 Potassium KMnO 4 158.03 ( 약산성 ) MnO 4- + 3e + 4H + MnO 2 + 2H 2 O 1.695 3 permanganate ( 알칼리성 ) MnO 4- + 3e + 2H 2 O MnO 2 + 4OH - 0.588 3 황산제이세륨암모늄사수화물 Ammonium cerium(iv) sulfate tetrahydrate Ce(SO 4 ) 2 2(NH 4 ) 2 SO 4 4H 2 O 668.56 Ce 4+ + e Ce 3+ 1.61 1 요오드 iodine 중크롬산칼륨 Potassium dichromate I 2 253.81 I 2 + 2e 2I - ; 0.5355 2 K 2 Cr 2 O 7 294.18 Cr 2 O 7 +6e+14H + 2Cr 3+ +7H 2 O 1.33 6 브롬산칼륨 Potassium bromate KBrO 3 167.00 BrO 3- + 6e + 6H + Br - + 3H 2 O BrO 3- + 5e + 6H + ½Br 2 (aq) + 3H 2 O 1.44 1.52 6 5 요오드산칼륨 Potassium iodate KIO 3 214.00 IO 3- + 6e + 6H + I - + 3H 2 O IO 3- + 5e + 6H + ½I 2 + 3H 2 O IO 3- + 4e + 6H + + Cl - ICl + 3H 2 O 1.085 1.195 1.23 6 5 4 아질산나트륨 Sodium nitrite NaNO 2 69.00 R-NH 2 + HNO 2 + HCl R-N NCl + 2H 2 O HNO 2 (aq)+ H + + e NO(g) + H 2 O 0.99 1

7. 환원제의종류와성질 환원제화학식식량반응 E o (V) 당량수 황산제이철암모늄육수화물 Ammonium iron(ii) sulfate hexahydrate FeSO 4. (NH 4 ) 2 SO 4. 6H 2 O 392.13 Fe 3+ + e Fe 2+ 0.771 1 삼염화티탄 Titanium trichloride TiCl 3 154.26 TiO 2+ + e + 2H + Ti 3+ + H 2 O 0.099 1 삼산화비소 Arsenic trioxide As 2 O 3 197.84 AsO 4 3- + e + 2H 2 O AsO + 4OH - -0.71 4 옥살산이수화물 Oxalic acid dihydrate 티오황산나트륨오수화물 Sodium thiosulfate pentahydrate H 2 C 2 O 4. 2H 2 O 126.07 2CO 2 (g) + 2H + + 2e H 2 C 2 O 4 (aq) -0.49 2 Na 2 S 2 O 3. 5H 2 O 248.17 S 4 O 6 + 2e 2S 2 O 3 0.08 1 15

출처 4

출처 1) 출처 1 - http://staff.norman.k12.ok.us/~cyohn/index_files/displacementlab.htm 2) 출처 2 - Quantitative Chemical Analysis, Daniel C. Harris, 2012 8th Ed 3) 출처 3 - http://wps.prenhall.com/wps/media/objects/602/616516/media_assets/chapter18/text_images/fg18_05-01un.jpg 4) 출처 4- 의약품분석학, 약품분석학분과회, 2012 17