无机化学-04-4-元素标准电极电势图(A)课件.ppt

单击此处编辑母版标题样式,,单击此处编辑母版文本样式,,第二级,,第三级,,第四级,,第五级,,,*,4.4,电势图及其应用,,第,4,章,,氧化还原反应,,把同一元素不同氧化数物质所对应电对的标准电极电势，按各物质的氧化值由高到低的顺序排列，并在两种物质之间标出对应电对的标准电极电势定义,4.4.1,元素标准电极电势图及其应用,O,2,H,2,O,2,H,2,O,0.695,,1.763,A,1.229,E,/V,O,2,HO,2,H,2,O,E,B,/V,-0.076,,0.867,0.401,-,1.,元素电势图,,Fe,3+,,Fe,2+,,Fe,0.771,,-0.441,-0.037,A,E,/V,,,Fe,3+,/Fe,2+,,Fe,2+,/Fe,,Fe,3+,/Fe,Fe,3+,+ e,-,,,Fe,2+,Fe,3+,+ 3e,-,,,Fe,Fe,2+,+ 2e,-,,,Fe,,2.,应用 ：,n,、,n,1,、,n,2,、,n,3,分别为各电对中氧化型,,与还原型的氧化数之差,,E,E,E,n,1,,n,2,,n,3,n,1,2,3,E,A,,B,,C D,n,,=,n,1,+,,n,2,+,n,3,,E,E,1,E,2,E,3,,①,计算电对的标准电极电势,=,n,1,+,,n,2,+,n,3,,n,E,E,1,E,2,E,3,,,BrO,3,-,,BrO,-,,Br,2,Br,-,? ?,1.605,=,,2,×,0.76 - 1.605,1,=,0.455V,(BrO,-,/Br,2,),=,1,,2,(,BrO,-,/Br,-,) -,,,(Br,2,/Br,-,),,E,E,E,6,2,4,,,,,0.76,0.61,例,E,/V,B,=,n,1,+,,n,2,+ n,3,,n,E,E,E,E,+5,+1,0,-1,1,,,,,1,,,,,,=,,6,×,0.61-,2,×,0.76,4,=,0.53V,(,BrO,3,-,/BrO,-,),=,E,4,,6,(,BrO,3,-,/Br,-,) –,2,,(,BrO,-,/Br,-,),,E,E,2,,BrO,3,-,,BrO,-,,Br,2,Br,-,4,,1,,,1,,?,0.455,,,1.605,0.76,0.61,E,/V,B,6,=,n,1,+,,n,2,+ n,3,,n,E,E,E,E,,②,判断能否发生歧化反应,氧化数升高或降低发生在,同一物质内同,,一元素,上的反应称为,歧化反应,。

Cl,2,+H,2,O →,,HClO,+,HCl,,-1,0,+1,当一种元素处于中间氧化数时,,,它一部分向高的,,氧化数状态变化,(,被氧化,),,另一部分向低的氧化,,数状态变化,(,被还原,),，这类反应称为歧化反应,,,(,左,),,,,(,右,),,,,A,,B,,,C,结论,:,(,右,),,>,,(,左,),,,B,易发生歧化反应,,,,,产物是,A,,和,C,E,E,,(,右,),,<,,(,左,),,,A,,与,C,,可反歧化为,B,,E,E,E,E,,,2Cu,+,,→,Cu,2+,+ Cu,E,(Cu,2+,/Cu,+,),= 0.159V,E,(Cu,+,/Cu) =,0.520V,>,Cu,2+,,Cu,+,,Cu,0.159 0.520,,0.340,E,/V,A,,Cu,+,,易发生歧化反应,,0.56,,2.26,1.70,A,E,/V,MnO,4,-,,MnO,4,2,-,,,MnO,2,,Mn,3+,,Mn,2+,0.95,,1.51,1.23,,Fe + 2H,+,,→,Fe,2+,+ H,2,↑,③,解释元素的氧化还原特性,E,/V,A,Fe,3+,,Fe,2+,,Fe,,0.771,,-0.44,,如,(1),因,(Fe,2+,/Fe),,< 0,，,而,(Fe,3+,/Fe,2+,),,> 0,,E,E,故在非氧化性稀酸,(,如稀盐酸或稀硫酸,),中,,金属铁只能被氧化为,Fe,2+,,(2),因,(,O,2,/H,2,O,),=1.229V,>,,,(Fe,3+,/Fe,2+,),,4Fe,2+,+ O,2,+ 2H,+,,→,4Fe,3+,+ 2H,2,O,所以,Fe,2+,在空气中不稳定,,易被空气中氧氧化为,Fe,3+,E,/V,A,Fe,3+,,Fe,2+,,Fe,0.771,,-0.44,,E,E,,因,Fe,2+,不会发生歧化反应,,可发生歧化反应的逆反应,在,Fe,2+,盐溶液，加入少量金属铁,,能避免,Fe,2+,空气中氧气氧化为,Fe,3+,,Fe + 2Fe,3+,,→,3Fe,2+,,如,E,/V,A,Fe,3+,,Fe,2+,,Fe,,,0.771 -0.44,,,④,判断,氧化还原的产物,MnO,4,-,,,MnO,2,,1.70,,1.23,,,,,Mn,2+,例：已知锰和碘的元素电势图,IO,3,-,,I,2,1.20,,0.53,,,,I,-,E,/V,A,,MnO,4,-,,,MnO,2,,1.70,,1.23,,,,,Mn,2+,IO,3,-,,I,2,1.20,,0.53,,,,I,-,E,/V,A,,,MnO,4,-,+I,-,+ 2H,+,→ Mn,2+,,+ IO,3,-,+H,2,O,在酸性溶液中，,KMnO,4,,与,KI,反应,,MnO,4,-,,,MnO,2,,1.70,,1.23,,,,,Mn,2+,IO,3,-,,I,2,1.20,,0.53,,,,I,-,E,/V,A,,2MnO,4,-,+I,-,+ 2H,+,→ 2MnO,2,+ IO,3,-,+H,2,O,KMnO,4,,过量,KI,过量,,2MnO,4,-,+10I,-,+16H,+,→ 2Mn,2+,,+ 5I,2,,+ 8H,2,O,,,第,4,章,,氧化还原反应,第,4,节,,结束,,。