Izinga lokusabela nemithetho yezinga: indlela ukugxila okulawula ngayo isivinini

Ukulinganisa ukuthi ukusabela kuhamba ngokushesha kangakanani

Izinga lokusabela wushintsho ekugxileni kwesisabelo noma komkhiqizo ngeyunithi ngayinye yesikhathi, ngokuvamile ngo-mol L⁻¹ s⁻¹. Ukugxila kwezisabelo kuyehla njengoba ukusabela kuqhubeka, ngakho ushintsho lwazo lubi. Uphawu lokususa lubekwa phambi kwezingxenye zezisabelo ukuze wonke amazinga abikwe njengezinombolo ezinhle.

Izinga elimaphakathi wushintsho ekugxileni esikhathini esithile luhlukaniswe ngobude baleso sikhathi. Izinga lesikhashana liwumqansa we-tangent ejikeni lokugxila nesikhathi ngomzuzwana owodwa. Izinga lokuqala yizinga lesikhashana ngesikhathi esiyi-zero, ngaphambi kokuthi imikhiqizo inqwabelane. Ekusabeleni okuningi izinga liyehla njengoba isikhathi sihamba, ngoba izisabelo ziyasetshenziswa.

Ukugxila kungenye yezinto eziningana ezinquma izinga. Izinga lokushisa, ama-catalyst, indawo engaphezulu yesisabelo esiqinile, nohlobo lwamakhemikhali lwezisabelo nakho kubalulekile. Lesi sihlahlandlela sigcina izinga lokushisa lingaguquki futhi sigxile ekugxileni; umphumela wezinga lokushisa uyisihloko sesihlahlandlela samandla e-activation.

Ukusabela okukodwa, izinga elilodwa: ukuhlukanisa ngama-coefficient

Izinhlobo ezihlukene ekusabeleni okufanayo zishintsha ngamajubane ahlukene, ngokulingana nama-coefficient azo. Ukuze unikeze izinga elilodwa lako konke ukusabela, hlukanisa izinga loshintsho lohlobo ngalunye nge-coefficient yalo. Ku-aA + bB → cC + dD, izinga lokusabela lingu-−(1/a)Δ[A]/Δt = −(1/b)Δ[B]/Δt = (1/c)Δ[C]/Δt = (1/d)Δ[D]/Δt.

Isibonelo esisebenzile 1. Ekubolweni 2 N₂O₅(g) → 4 NO₂(g) + O₂(g), i-nitrogen dioxide yakheka ngo-6.0 × 10⁻⁵ mol L⁻¹ s⁻¹ ngomzuzwana othile. Izinga lokusabela lingu-(1/4)(6.0 × 10⁻⁵) = 1.5 × 10⁻⁵ mol L⁻¹ s⁻¹. I-N₂O₅ isetshenziswa ngokuphindwe kabili izinga lokusabela, 3.0 × 10⁻⁵ mol L⁻¹ s⁻¹, kanti i-O₂ yakheka ngezinga lokusabela, 1.5 × 10⁻⁵ mol L⁻¹ s⁻¹. Zonke izitatimende ezine zichaza isenzakalo esifanayo.

Ukubala okufanayo kusebenza emazingeni amaphakathi. Ake sithi, njengomfanekiso, u-[N₂O₅] wehla esuka ku-0.0200 mol/L eya ku-0.0169 mol/L kuma-300 s okuqala. Izinga elimaphakathi lokusetshenziswa kwe-N₂O₅ lingu-(0.0200 − 0.0169)/300 s = 1.0 × 10⁻⁵ mol L⁻¹ s⁻¹. Ukususa kushiya izinombolo ezibalulekile ezimbili kuphela, ngakho umphumela unezimbili. Esikhathini esifanayo i-NO₂ yakheka ngokuphindwe kabili izinga elimaphakathi elingayisiwe, 2 × 1.03 × 10⁻⁵ = 2.1 × 10⁻⁵ mol L⁻¹ s⁻¹.

Ukubhala umthetho wezinga: i-rate constant nama-oda okusabela

Umthetho wezinga uveza izinga njengomkhiqizo wokugxila okuphakanyiswe emandleni: izinga = k[A]ᵐ[B]ⁿ. I-rate constant k iqondene nokusabela okukodwa ezingeni lokushisa elilodwa futhi ayincikile ekugxileni. Ama-exponent m no-n angama-oda okusabela maqondana no-A no-B, futhi isamba sawo siyi-oda lilonke. Ama-oda ngokuvamile angu-0, 1 noma 2, kodwa kubonakala nama-oda ayizingxenye nangemabi.

I-oda ngalinye likutshela ukuthi izinga lisabela kanjani ekushintsheni kokugxila okukodwa. Uma ukusabela kuyi-oda le-zero ku-A, ukushintsha u-[A] akunamthelela ezingeni. Uma kuyi-oda lokuqala, ukuphinda kabili u-[A] kuphinda kabili izinga. Uma kuyi-oda lesibili, ukuphinda kabili u-[A] kuphindaphinda izinga ngo-2² = 4. Uma izinga = k[A]²[B], ukuphinda kabili u-[A] ngenkathi wehlisela u-[B] engxenyeni kushintsha izinga ngesici esingu-2² × ½ = 2.

Ama-oda kufanele alinganiswe. Isigaba 12.3 se-OpenStax sinikeza ukusabela NO₂(g) + CO(g) → NO(g) + CO₂(g) njengesibonelo: umthetho wako wezinga uthi izinga = k[NO₂]², i-oda lesibili ku-NO₂ ne-oda le-zero ku-CO, nakuba isisabelo ngasinye sine-coefficient engu-1.

Indlela yamazinga okuqala, isinyathelo ngesinyathelo

Indlela yamazinga okuqala yenza ukusabela okufanayo izikhathi eziningana ezingeni lokushisa elilodwa, ishintsha ukugxila okukodwa kokuqala ngesikhathi, futhi ilinganise izinga ekuqaleni ngqo kokwenziwa ngakunye.

Isibonelo esisebenzile 2. Idatha lapha iyisibonelo, eyakhelwe ukuzijwayeza. Ku-A + 2 B → imikhiqizo, ukwenziwa okuthathu kunikeza: isivivinyo 1, [A] = 0.0100 mol/L no-[B] = 0.0100 mol/L, izinga lokuqala 2.40 × 10⁻⁶ mol L⁻¹ s⁻¹; isivivinyo 2, [A] = 0.0150 mol/L no-[B] = 0.0100 mol/L, izinga 5.30 × 10⁻⁶ mol L⁻¹ s⁻¹; isivivinyo 3, [A] = 0.0100 mol/L no-[B] = 0.0300 mol/L, izinga 7.30 × 10⁻⁶ mol L⁻¹ s⁻¹.

U-[A] kuphela oshintshayo phakathi kwezivivinyo 1 no-2, ngesici esingu-1.50, futhi izinga likhuphuka ngesici esingu-2.208. Xazulula u-2.208 = 1.50ᵐ ngama-logarithm: m = ln 2.208 / ln 1.50 = 1.95. Amazinga alinganisiwe aphethe iphutha lokuhlola, ngakho inani elisondele kangaka enombolweni ephelele liyayiswa: m = 2. U-[B] kuphela oshintshayo phakathi kwezivivinyo 1 no-3, ngesici esingu-3.00, futhi izinga likhuphuka ngo-3.04, ngakho n = ln 3.04 / ln 3.00 = 1.01, okuyiswa ku-1. Umthetho wezinga uthi izinga = k[A]²[B], i-oda lesithathu lilonke. Qaphela ukuthi u-B une-coefficient engu-2 esibalweni kodwa uyi-oda lokuqala.

Manje thola u-k esivivinyweni ngasinye: k = izinga / ([A]²[B]). Amanani amathathu angu-2.40, 2.36 no-2.43 L² mol⁻² s⁻¹, nesilinganiso esingu-2.40, ngakho bika k = 2.4 L² mol⁻² s⁻¹. Usebenzise ukubikezela izinga lapho [A] = 0.0200 mol/L no-[B] = 0.0250 mol/L: izinga = 2.4 × (0.0200)² × 0.0250 = 2.4 × 10⁻⁵ mol L⁻¹ s⁻¹.

• Khetha izivivinyo ezimbili lapho ukugxila okukodwa kuphela okushintshayo.
• Hlukanisa izinga elikhulu ngelincane nokugxila okuhambisanayo ngendlela efanayo. Bese uxazulula: isilinganiso samazinga = (isilinganiso sokugxila) siphakanyiswe emandleni e-oda.
• Yisa i-oda ngalinye enanini elinengqondo (inombolo ephelele, noma ngezinye izikhathi u-½) bese uphinda kwezinye izisabelo.
• Bala u-k esivivinyweni ngasinye bese uthola isilinganiso semiphumela, kunokuthemba ukwenziwa okukodwa.

Amayunithi ka-k aveza i-oda lilonke

Izinga lihlala linamayunithi okugxila ngesikhathi, ngakho amayunithi ka-k kufanele enze umthetho wezinga ulingane. Uma ukugxila kungu-mol/L nesikhathi singamasekhondi, u-k unamayunithi angu-(mol/L)¹⁻ⁿ s⁻¹, lapho u-n eyi-oda lilonke. Ukufunda amayunithi e-rate constant enikeziwe kuyindlela esheshayo yokwazi i-oda lilonke lokusabela.

• I-oda le-zero: mol L⁻¹ s⁻¹.
• I-oda lokuqala: s⁻¹, ngaphandle kweyunithi yokugxila nhlobo.
• I-oda lesibili: L mol⁻¹ s⁻¹.
• I-oda lesithathu: L² mol⁻² s⁻¹, njengasesibonelweni esisebenzile 2.

Kungani isibalo esilinganisiwe singakwazi ukunikeza ama-oda

Ukusabela okuningi kwenzeka ngochungechunge lwezehlakalo ezilula ezibizwa ngokuthi izinyathelo eziyisisekelo, ezakha ndawonye i-mechanism. Esinyathelweni esisodwa esiyisisekelo, futhi kuphela kuso, umthetho wezinga ungabhalwa kusukela kuma-coefficient esinyathelo: isinyathelo lapho amamolekyuli amabili e-NO₂ eshayisana khona siyi-oda lesibili ku-NO₂. Inani lezinhlayiya ezishayisanayo esinyathelweni yi-molecularity yaso.

Isinyathelo esihamba kancane kakhulu ku-mechanism sikhawulela izinga lilonke futhi sibizwa ngokuthi isinyathelo esinquma izinga. Isigaba 12.6 se-OpenStax sichaza umthetho wezinga we-NO₂ + CO ngale ndlela. Isinyathelo sokuqala esihamba kancane, NO₂ + NO₂ → NO₃ + NO, silandelwa yisinyathelo esisheshayo, NO₃ + CO → NO₂ + CO₂. Lezi zinyathelo ezimbili zihlangana zibe yisibalo sisonke. I-CO ingena kuphela ngemva kwesinyathelo esihamba kancane, ngakho ukugxila kwayo akuveli emthethweni wezinga. Isibalo sisonke esilinganisiwe sichaza okusetshenziswayo nokukhiqizwayo, hhayi ukuthi ukusabela kwenzeka kanjani, yingakho ama-oda kufanele alinganiswe.

Amaphutha omthetho wezinga nendlela yokuwabamba

Amaphutha amaningi ezinkingeni ze-kinetics avela ekufundeni isibalo esilinganisiwe sengathi umthetho wezinga, noma ekuthatheni izinga lohlobo ngalunye njengenombolo efanayo.

• Ukuthatha ama-oda okusabela kuma-coefficient esibalo sisonke. Ama-oda avela kudatha noma ku-mechanism eyaziwayo.
• Ukukhohlwa ukuhlukanisa ngama-coefficient lapho uguqula izinga lohlobo olulodwa libe izinga lolunye.
• Ukushiya uphawu lokususa ezingeni lesisabelo futhi ubike izinga lokusabela elibi.
• Ukuqhathanisa izivivinyo ezimbili lapho ukugxila okungaphezu kokukodwa kushintshe ngesikhathi esisodwa.
• Ukubala u-k ngaphandle kwamayunithi. Amayunithi akhe aqinisekisa ukuthi i-oda lilonke lilungile yini.
• Ukuyisa i-oda elilinganisiwe elingu-1.95 ku-1.9 esikhundleni sika-2. Idatha evela ekuhloleni ayivamile ukunikeza izinombolo eziphelele ezinembile.