氧化還原講義

1、高一化學(xué)第二學(xué)期期末復(fù)習(xí) 氧化還原反應(yīng)一.氧化還原反應(yīng)（1）氧化還原反應(yīng)的本質(zhì)_ 特征_ 判斷依據(jù)：_例1.氯化碘（icl）的性質(zhì)類似鹵素，有很強的化學(xué)活動性。icl跟zn、h2o的反應(yīng)如下：2icl+2zn=zncl2+zni2 icl+h2o=hcl+hio下列敘述中正確的是（ ）a反應(yīng)不是氧化還原反應(yīng) b反應(yīng)不是氧化還原反應(yīng)c二者都是氧化還原反應(yīng) d在反應(yīng)中，zn發(fā)生的是氧化反應(yīng)（2）氧化還原反應(yīng)的相關(guān)概念氧化劑有氧化性化合價降低得電子被還原還原反應(yīng)還原產(chǎn)物還原劑有還原性化合價升高失電子被氧化氧化反應(yīng)氧化產(chǎn)物氧化劑還原劑不是固定不變的，同一物質(zhì)在不同反應(yīng)中可以扮演不同角色。說明：氧化劑和

2、還原劑均是指反應(yīng)物，是一種化學(xué)物質(zhì)，而不是指某一種元素；氧化劑具有氧化性，氧化劑本身被還原，即發(fā)生還原反應(yīng)，轉(zhuǎn)化為還原產(chǎn)物；還原劑具有還原性，還原劑本身被氧化，即發(fā)生氧化反應(yīng)，轉(zhuǎn)化為氧化產(chǎn)物。例2.在cu+2h2so4（濃）=cuso4+so2+2h2o反應(yīng)中，_是氧化劑；_是還原劑；_元素被氧化；_元素被還原；_是氧化產(chǎn)物；_是還原產(chǎn)物；電子轉(zhuǎn)移總數(shù)為_。例3. 氮化鋁（aln，al和n的相對原子質(zhì)量分別為27和14）廣泛應(yīng)用于電子、陶瓷等工業(yè)領(lǐng)域。在一定條件下，aln可通過反應(yīng)al2o3n23c2aln3co合成。下列敘述正是（ ）a上述反應(yīng)中，n2是還原劑，al2o3是氧化劑b上述反應(yīng)中

3、，每生成1molaln需轉(zhuǎn)移3mol電子caln中氮元素的化合價為3daln的摩爾質(zhì)量為41g（2）四種基本反應(yīng)類型與氧化還原反應(yīng)的關(guān)系（如右圖）二、氧化還原反應(yīng)的表示方法及電子轉(zhuǎn)移數(shù)目（1）單線橋法。從被氧化（失電子，化合價升高）的元素指向被還原（得電子，化合價降低）的元素，標(biāo)明電子數(shù)目，不需注明得失。例：2e-mno2+4hcl（濃）mncl2+cl2+2h2o （2）雙線橋法。得失電子分開注明，從反應(yīng)物指向生成物（同種元素）注明得失及電子數(shù)。例：得2e-失2e-mno2+4hcl（濃）mncl2+cl2+2h2o失5e得5e3cl2+6kohkclo3+5kcl+3h2o 失5e-得5e

4、-歸中反應(yīng)。不同價態(tài)的同種元素的原子在反應(yīng)中趨于中間價態(tài)，解此類題最好將該元素的不同價態(tài)用數(shù)軸標(biāo)出，變化的區(qū)域只靠攏，不重疊。例：kclo3+6hcl3cl2+ 6kcl +3h2o 三、氧化還原反應(yīng)的一般規(guī)律1. 性質(zhì)強弱的規(guī)律(1) ne在“氧化劑還原劑 還原產(chǎn)物氧化產(chǎn)物”中，氧化性強弱順序是：氧化劑 氧化產(chǎn)物；還原性強弱順序是：還原劑 還原產(chǎn)物。例題、根據(jù)反應(yīng)式：(1)2fe3+2i-=2fe2+i2，(2)br2+2fe2+=2br-+2fe3+，可判斷出離子的還原性從強到弱的順序是( )。abr-、fe2+、i-bi-、fe2+、br- cbr-、i-、fe2+ dfe2+、i-、b

5、r-(2)根據(jù)金屬的活動性順序表來判斷還原性kcanamgalznfesnpbcuhgagptau 氧化性k+ca2+na+mg2+al3+zn2+fe2+sn2+pb2+cu2+fe3+hg2+zx單質(zhì)的還原性：yzx對應(yīng)離子的氧化性：xzy對應(yīng)離子的還原性：xzya只有 b只有c只有 d(4) 反應(yīng)原理相似的不同反應(yīng)中，反應(yīng)條件要求越低，說明氧化劑或還原劑越強。如鹵素單質(zhì)與h2的反應(yīng)，按f2、cl2、br2、i2的順序反應(yīng)越來越難，反應(yīng)條件要求越來越高，則可得出氧化性f2cl2 br2 i2 。cu4hno3(濃)=cu(no3)22no22h2o cu2h2so4(濃)cuso4so22

6、h2o氧化性：濃硝酸濃硫酸 (5)氧化性強弱順序：k+ca2+na+mg2+al3+zn2+fe2+sn2+pb2+cu2+fe3+hg2+i-br-cl-oh-no3- 、so42-等。 (6) 對同一元素而言，一般價態(tài)越高，氧化性越強，如fe3fe2fe；價態(tài)越低，氧化性越弱，如s2sso2。（特例：氧化性hclohclo2hclo3hclo4 ）（7）、依據(jù)“三度”判斷(“三度”即：濃度、溫度、酸堿度)一般地，濃度越大，溫度越高，氧化劑的氧化性(或還原劑的還原性)越強；酸堿度是影響氧化性強弱的重要因素。例如，kmno4在酸性條件下具有較強的氧化性，常溫下即可和濃鹽酸反應(yīng)制取氯氣；hno3

7、(濃)的氧化性大于hno3(稀)的氧化性；hno3(熱)的氧化性大于hno3(冷)的氧化性。例題：已知：向kmno4固體滴加濃鹽酸，產(chǎn)生黃綠色氣體；向fecl2溶液中通入少量實驗產(chǎn)生的氣體，溶液變黃色；取實驗生成的溶液滴在淀粉ki試紙上，試紙變藍(lán)，下列判斷正確的是()。a上述實驗證明氧化性：mnocl2 fe3i2b上述實驗中，共有兩個氧化還原反應(yīng)c實驗生成的氣體不能使?jié)駶櫟牡矸踜i試紙變藍(lán)d實驗證明fe2既有氧化性又有還原性2. 守恒規(guī)律（得失電子守恒） 失電子總數(shù)與得電子總數(shù)相等。例題、硫酸銨在強熱條件下分解,生成氨、二氧化硫、氮氣和水，反應(yīng)中生成的氧化產(chǎn)物和還原產(chǎn)物的物質(zhì)的量之比是( )

8、a.1:3 b.2:3 c.1:1 d.4:3說明：解這類題目不必都寫出完整并配平的氧化還原反應(yīng)方程式，關(guān)鍵是抓住本質(zhì)，厘清得失相等的關(guān)系。例題、24 ml濃度為0.05 mol/l的na2so3溶液恰好與20 ml濃度為0.02 mol/l的k2cr2o7溶液完全反應(yīng)。已知na2so3被k2cr2o7氧化為na2so4，則元素cr在還原產(chǎn)物中的化合價為（ ）。a、2 b、3 c、4 d、53.價態(tài)表現(xiàn)性質(zhì)的規(guī)律元素處于最高價，只有 ；元素處于最低價，只有 ；元素處于中間價態(tài)，既有 又有 。例題：在h+、mg2+ 、fe2+、fe3+、s2-、i-、s中，只有氧化性的是_，只有還原性的是_，既

9、有氧化性又有還原性的是_。4、轉(zhuǎn)化規(guī)律氧化還原反應(yīng)中，同種元素不同價態(tài)之間的氧化反應(yīng)，化合價的變化遵循“只靠攏，不交叉”（即價態(tài)歸中）；同種元素相鄰價態(tài)間不發(fā)生氧化還原反應(yīng)。例如：kclo3+6hcl=kcl+3cl2+3h2o 例題：對于反應(yīng)cah2+2h2o=ca(oh)2+2h2有下列判斷：h2只是氧化產(chǎn)物，h2只是還原產(chǎn)物，h2o是氧化劑，cah2中的h元素被還原，此反應(yīng)中的氧化產(chǎn)物和還原產(chǎn)物的分子個數(shù)之比為1:1。上述判斷正確的是（ ）a b c d5、反應(yīng)先后規(guī)律同一氧化劑與含多種還原劑(物質(zhì)的量濃度相同)的溶液反應(yīng)時，首先被氧化的是還原性較強的物質(zhì)；同一還原劑與含多種氧化劑(物質(zhì)

10、的量濃度相同)的溶液反應(yīng)時，首先被還原的是氧化性較強的物質(zhì)。如：將cl2通人物質(zhì)的量濃度相同的nabr和nai的混合液中，c12首先與nai反應(yīng)；將過量鐵粉加入到物質(zhì)的量濃度相同的fe3+和cu2+的混合溶液中，fe首先與fe3+反應(yīng)。 五、氧化還原反應(yīng)方程式的配平1配平原理在氧化還原反應(yīng)中，從現(xiàn)象看是化合價升降總數(shù)相等，從本質(zhì)看是電子得失總數(shù)相等，對離子方程式進(jìn)行配平時，除滿足上述要求外，還應(yīng)注意電荷守恒。2配平步驟(1)“標(biāo)價態(tài)”即先寫出反應(yīng)物和生成物的化學(xué)式，并標(biāo)出發(fā)生氧化還原反應(yīng)的元素的正負(fù)化合價。(2)“標(biāo)變化”即標(biāo)出元素的化合價的變化(升高或者降低)。待添加的隱藏文字內(nèi)容2(3)“

11、求總數(shù)”即使化合價升高和降低的總數(shù)相等。(4)用觀察的方法配平其他物質(zhì)的化學(xué)計量數(shù)。3抓住一個關(guān)鍵，掌握三個原則(1)一個關(guān)鍵準(zhǔn)確判斷并標(biāo)出變價元素的化合價，求出化合價升降數(shù)及其最小公倍數(shù)，進(jìn)而求得氧化劑、還原劑的計量數(shù)。(2)三個原則反應(yīng)前后各元素的原子個數(shù)相等。氧化劑得電子總數(shù)與還原劑失電子總數(shù)相等。反應(yīng)前后各帶電微粒所帶電荷總數(shù)相等(離子反應(yīng))。例題：（2）某廠廢水中含kcn，其濃度為650mgl-1現(xiàn)用氯氧化法處理，發(fā)現(xiàn)如下反應(yīng)(其中n均為-3價)：請配平下列化學(xué)方程式： kcn+ koh+ cl2 kocn+ kcl+ h2okmno4+feso4+h2so4=fe2(so4)3+m

12、nso4+k2so4+h2owinger tuivasa-sheck, who scored two tries in the kiwis 20-18 semi-final win over england, has been passed fit after a lower-leg injury, while slater has been named at full-back but is still recovering from a knee injury aggravated against usa.both sides boast 100% records heading into

13、 the encounter but australia have not conceded a try since josh charnleys effort in their first pool match against england on the opening day.aussie winger jarryd hayne is the competitions top try scorer with nine, closely followed by tuivasa-sheck with eight.but it is recently named rugby league in

14、ternational federation player of the year sonny bill williams who has attracted the most interest in the tournament so far.the kiwi - with a tournament high 17 offloads - has the chance of becoming the first player to win the world cup in both rugby league and rugby union after triumphing with the a

15、ll blacks in 2011.id give every award back in a heartbeat just to get across the line this weekend, said williams.the (lack of) air up there watch mcayman islands-based webb, the head of fifas anti-racism taskforce, is in london for the football associations 150th anniversary celebrations and will a

16、ttend citys premier league match at chelsea on sunday.i am going to be at the match tomorrow and i have asked to meet yaya toure, he told bbc sport.for me its about how he felt and i would like to speak to him first to find out what his experience was.uefa hasopened disciplinary proceedings against

17、cskafor the racist behaviour of their fans duringcitys 2-1 win.michel platini, president of european footballs governing body, has also ordered an immediate investigation into the referees actions.cska said they were surprised and disappointed by toures complaint. in a statement the russian side add

18、ed: we found no racist insults from fans of cska. baumgartner the disappointing news: mission aborted.the supersonic descent could happen as early as sunda.the weather plays an important role in this mission. starting at the ground, conditions have to be very calm - winds less than 2 mph, with no pr

19、ecipitation or humidity and limited cloud cover. the balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere) where our day-to-day weather lives. it will climb higher than the tip of mount everest (5.5 miles/8.85 kilometers), drifting even higher than the

20、 cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. as he crosses the boundary layer (called the tropopause),e can expect a lot of turbulence.the balloon will slowly drift to the edge of space at 120,000 feet ( then, i would assume, he will slowly step o

21、ut onto something resembling an olympic diving platform.they blew it in 2008 when they got caught cold in the final and they will not make the same mistake against the kiwis in manchester.five years ago they cruised through to the final and so far history has repeated itself here - the last try they

22、 conceded was scored by englands josh charnley in the opening game of the tournament.that could be classed as a weakness, a team under-cooked - but i have been impressed by the kangaroos focus in their games since then.they have been concentrating on the sort of stuff that wins you tough, even contests - strong defence, especially on their own goal-line,