Uvavanyo lwebhotile eluhlaza okwesibhakabhaka: ikhemistri, inkqubo, nokuqwalaselwa

Ibhotile ecacileyo ihleli ebhentshini. Ijongeka njengamanzi. Umntu uyayishukumisa, ulwelo lujike lube luhlaza okwesibhakabhaka oqaqambileyo. Xa ibekwe phantsi, umbala oluhlaza okwesibhakabhaka uyaphela kwisithuba somzuzu omnye okanye emibini. Yishukumise kwakhona, umbala ubuye. Ukuzaliswa kube kanye kunokuphinda oku izihlandlo ezingamashumi amabini okanye ngaphezulu.

Abafundi badla ngokuqikelela ukuba kukho into ebifihlwe ebhotileni, okanye ukuba ukushukumisa kudibanise iileya ezimbini. Zombini ezi ngqikelelo ziyasilela ngendlela efundisayo. Umbala uvela kwidayi enye, i-methylene blue, ekhoyo kulo lonke ulwelo. Into etshintshayo linani lee-electron ezithwalwa yidayi. Lo mboniso ngumjikelo we-redox obonakala ngamehlo, kwaye yonke into eguquguqukayo ebonwa yiklasi—ixesha lokushukumisa, iqondo lobushushu, ugxininiso—ihambelana nenxalenye ethile yekhemistri.

Iifom ezimbini zedayi enye

I-methylene blue ene-oxidation yinkqubo yeeringi ethe tyaba, enentlawulo entle. Ifunxa ngamandla malunga ne-600 ukuya ku-700 nanometres, nto leyo iliso eliyibona njengombala oluhlaza okwesibhakabhaka onzulu. Ezi fom zimbini kunye neespektra zazo zichazwe kwisikhokelo sesakhiwo neempawu ze-methylene blue.

I-reduction yongeza ii-electron ezimbini kunye ne-proton, ivelise i-leucomethylene blue: engenantlawulo, engathe tyaba, kwaye phantse ingenambala. Kwisisombululo se-alkaline i-half-reaction ibhalwa MB+ + H2O + 2 e- ⇌ LMB + OH-. Eli nyathelo libuyiselwa ngokupheleleyo. Umbala oluhlaza okwesibhakabhaka uthetha i-oxidised, ukungabi nombala kuthetha i-reduced, kwaye akukho meko yesithathu ekufuneka ilandelwe, nto leyo eyenza oku kube yindlela ecocekileyo yokuqala ukufunda ikhemistri ye-redox.

Umjikelo: i-glucose iyareduce, i-oxygen iphinde iyioxidise

Ibhotile inezithako ezintathu ezisebenzayo: i-methylene blue, i-glucose, kunye ne-alkali enamandla, i-potassium okanye i-sodium hydroxide. I-alkali ikhuthaza i-glucose ukuba ibe ziifom ezisebenzayo ezilahlekelwe yi-proton nezinikela ii-electron kwidayi:

reducing sugar + MB (blue, oxidised) -> oxidised sugar products + LMB (colourless)

Eli nyathelo licothayo lisusa umbala ngoxa ibhotile imi. I-glucose ngumnikeli osisibingelelo kwaye iyasetyenziswa. Idayi idlulisa nje ii-electron, ngoko amathontsi ambalwa anele ukusebenza kwibhotile yonke. Iingcaciso ezindala zaseklasini zithi i-glucose iba yi-gluconic acid. Le ndlela imfutshane yokuchaza iyakwazi ukuqikelela oko kuqwalaselwayo, kodwa abafundisi kufuneka bazi ukuba ayiphelelanga: uhlalutyo lomatshini olupapashwe kwi-Royal Society Open Science lulandela i-oxidation ukusuka kwi-enediolate esebenzayo ukuya kwi-dicarbonyl eqhekeka ibe zii-asidi ezincinci.

Ukushukumisa kubuyisela umva oko kubonakalayo. Ukunyakaziswa kunyibilikisa i-oxygen esuka kwisithuba somoya esivaliweyo esingentla kolwelo, kwaye i-oxygen iphinda iyioxidise idayi ene-reduction:

LMB (colourless) + O2 -> MB (blue) + reduced oxygen products

Xa ishiywe imi, i-oxygen enyibilikileyo iyaphela, i-glucose iphinde iyireduce idayi, uze umbala uphele. Emva kwemijikelo emininzi, ikhemistri iyonke kukwenziwa kwe-oxidation yeswekile ngumoya, ngoxa idayi ijikeleza ingatshintshanga njengomlamli we-redox. Ngumlamli endaweni yokuba yi-catalyst engqongqo, kuba i-oxidation yeswekile iyaqhubeka nangaphandle kwayo, kwaye ukuphela kombala asikokubola: idayi etshatyalalisiweyo ibingenakuvuselelwa ngokushukunyiswa. Ukuze ugcine izisombululo ezigxininisiweyo zedayi zizinzile phakathi kwemiboniso, jonga amanqaku okuphatha nokugcina izisombululo ze-methylene blue.

Inkqubo yomboniso ophantsi kolawulo

Lo ngumboniso ophantsi kolawulo, hayi umsebenzi wasekhaya. I-alkali ifuna ukhuseleko lwamehlo, iiglavu, kunye nomfundisi olawula ukulungiselela nokucoca. Iindlela ezimbini ezibhaliweyo ziyavumelana ngesakhiwo kodwa zahluke ngobungakanani.

Iphepha lemiyalelo elisemva komboniso njengoko upapashwe lisebe lekhemistri lase-Indiana University lisebenzisa malunga ne-5 percent potassium hydroxide, 4 percent glucose, kunye ne-1 percent aqueous methylene blue. Galela imithamo elinganayo yezisombululo ze-alkali ne-glucose kwibhotile ecacileyo ye-250 okanye 500 millilitre de izale ukuya kwisiqingatha, ushiye indawo eseleyo njengesithuba somoya. Yongeza amathontsi ambalwa edayi, vala ngesiciko, tywina indawo edibanayo, uze uyiyeke ime de umbala oluhlaza okwesibhakabhaka uphele. Inkqubo ye-Royal Society of Chemistry inyusa umlinganiselo wale ngcamango inye iye kwiflask ye-1 litre evalwe ngesiciko: 300 millilitres zamanzi, 10 grams ze-glucose, 8 grams ze-potassium hydroxide (okanye 6 grams ze-sodium hydroxide), kunye nee-millilitres ezimbalwa zesisombululo sedayi esixutywe kancinci.

Ukuwenza umboniso, yishukumise ngamandla. Umbala opheleleyo oluhlaza okwesibhakabhaka uvela kwimizuzwana embalwa. Beka iflask phantsi uze ulinganise ixesha lokuphela kombala. I-Royal Society of Chemistry ixela imijikelo engaphezu kwamashumi amabini ngokuzaliswa kube kanye. Ungaze uzalise ibhotile iye kufika kanye emlonyeni: ngaphandle komoya ovalelekileyo akukho gcino lwe-oxygen olunokunyibilika.

Into emayiqwalaselwe, nezinto ezitshintsha ixesha

Linganisa izinto ezintathu: ixesha lokushukumisa de ibe luhlaza okwesibhakabhaka ngokupheleleyo (seconds), ixesha lokuma de ingabi nombala (ukuya kwimizuzu embalwa), kunye nenani lemijikelo ngaphambi kokuba umbala oluhlaza okwesibhakabhaka ube buthathaka. Xa ukusondela esiphelweni sokuphela kombala kumjikelo ngamnye, jonga umphezulu. Umaleko omncinci oluhlaza okwesibhakabhaka udla ngokuhlala kumda womoya nolwelo, apho i-oxygen iqhubeka isasazeka ingene ngaphakathi. Loo mgca kukusasazeka okubonakalayo.

Iriyakhshini yebhotile eluhlaza okwesibhakabhaka ilandela lo mthetho wesantya ofunyenwe ngamalinge ochazwe kunye nenkqubo ye-Royal Society of Chemistry: rate = k[MB oxidised][glucose]OH-. Ilungu ngalinye lingaba luvavanyo lwaseklasini. I-glucose eninzi, i-alkali eninzi, okanye idayi eninzi zinciphisa ixesha lombala oluhlaza okwesibhakabhaka. Ubushushu bukhawulezisa ukuphela kombala; iflask ebandayo isabela kade. Ukushukumisa ngamandla ngakumbi kunyibilikisa i-oxygen eninzi, ngoko umbala oluhlaza okwesibhakabhaka uhlala ixesha elide. Isithuba somoya esikhulu sandisa ixesha lokusebenza. Xa ekugqibeleni imijikelo isiba buthathaka kwaye ulwelo lujika lube tyheli, iswekile iphelile kwaye iimveliso ezisecaleni ziqokelelekile. Eso siphelo sisiphumo esifanele ukubhalwa.

Iphepha lomsebenzi lokuqwalasela

Khuphela le theyibhile kwiincwadi zamanqaku, umqolo omnye kuvavanyo ngalunye. Eli phepha lomsebenzi kunye nomzobo weriyakshini ongentla zizixhobo eziprintwayo zeli nqaku.

Imibuzo yokuqikelela, ephendulwa ngaphambi kovavanyo ngalunye:

• Ibhotile iluhlaza okwesibhakabhaka kanye emva kokushukunyiswa. Yeyiphi ifom yedayi eyongameleyo, kwaye yintoni eyibeke kuloo meko?
• Ibhotile iyema kwaye umbala uyaphela. Yeyiphi iriyakhshini eyongameleyo, kwaye sesiphi isithako esisetyenziswayo?
• Emva kwemijikelo emininzi umbala oluhlaza okwesibhakabhaka uba buthathaka uze ubonakale utyheli. Ngaba kufuneka uwuvuselele ngedayi, i-alkali, okanye i-glucose, kwaye kutheni?
• Zoba igrafu yombala ngokuchasene nexesha kumjikelo omnye. Phawula indawo apho i-oxygen ingena khona kwisisombululo.

Iimpendulo zomfundisi: (1) i-methylene blue ene-oxidation, ephinde yenziwa i-oxidation yi-oxygen enyibilikileyo evela kwisithuba somoya; (2) i-reduction eyenziwa yi-glucose, i-glucose iyasetyenziswa; (3) i-glucose, umnikeli ongumda, kuba idayi ijikeleza ingatshintshanga; (4) ukunyuka okukhawulezayo xa kushukunyiswa, ukuhla ngokuthe ngcembe xa imi, ukungena kwe-oxygen kwenzeka kuphela ngexesha lokunyuka.

Izalamane ezisondeleyo ezifanele ukukhankanywa

Umboniso wesibane sendlela usebenzisa i-indigo carmine endaweni yayo uze udlule kumbala otyheli, obomvu, noluhlaza xa kufakwa i-oxygen. Igama elithi green bottle lisetyenziswa ngokubanzi: ngamanye amaxesha libhekisa kolo hlobo, ngamanye amaxesha libhekisa kwiifomyula eziluhlaza ngakumbi ezifana neenkqubo ze-ascorbic acid okanye inkqubo yokujikeleza esebenzisa ii-enzyme echazwe yi-American Chemical Society. Xela ngokucacileyo ukuba loluphi uhlobo olusebhentshini ukuze abafundi bangadibanisi oko bakuqwalaseleyo kwiikhemistri ezahlukeneyo.

Ukhuseleko nokuphatha

Makubekho ulawulo ngalo lonke ixesha. Sebenzisa ukhuseleko lwamehlo ngokuchasene nokutshiza kweekhemikhali kunye neiglavu xa uphatha isisombululo se-alkaline okanye ushukumisa isitya esivaliweyo. I-alkali iyatshisa, idayi iyangcolisa ulusu nelaphu, kwaye izisombululo ezigxininisiweyo zedayi ezenziwe nge-ethanol zongeza isinyibilikisi esinokutsha ebhentshini. Gcina isitya sivaliwe ngoxa usishukumisa. Emva koko, gcina izisombululo ezisetyenzisiweyo ukuze ziphathwe ngokwemithetho yelabhoratri yeziko lakho. Iimfuno zenkunkuma ye-alkaline enedayi ziyahluka phakathi kwamaziko nemimandla yomthetho, ngoko landela inkqubo yelabhoratri yakho endaweni yokuthatha inkqubo komnye umthombo.

Ukuba ufuna amanani endaweni yeenguqu zombala, iimvavanyo zobungakanani be-methylene blue ziqhubeka apho lo mboniso uphela khona.

Kutheni ootitshala beqhubeka besebenzisa le bhotile

Iflask enye idibanisa iingcamango ezine. I-redox iba ngumbala endaweni yokuba ibe yinkcazelo nje. Umlamli ubonisa indlela isixa esincinci sento enye esinokubonisa ngayo imeko yesixa esikhulu senye. I-kinetics iyahlukana ne-thermodynamics ngendlela ebonakalayo: i-oxygen iyongamela ngoxa ukushukumisa kuyinikezela, i-glucose iyongamela xa unikezelo luyeka. Kwaye ukusasazeka, enye yeenkqubo ezolileyo kwikhemistri, kuko okuqhuba wonke umboniso, kuba ukuqaqamba ngakunye kombala oluhlaza okwesibhakabhaka kuqala xa i-oxygen iwela isuka emoyeni ingena emanzini. Umboniso ovumela abafundi ukuba baqikelele, balinganise ixesha, baze bacacise konke oko ngesitophuwotshi netheyibhile uyifanele indawo yawo ebhentshini.