Uyini uMthetho kaRaoult kuKhemistri?
Kumakhemikhali, ikakhulukazi ekufundweni kwezixazululo kanye nezakhiwo zomzimba zezingxube, kunomqondo obalulekile ovame ukusetshenziswa ukuchaza ukuthi umfutho womusi wento ushintsha kanjani uma uxutshwa nenye into. Lo mqondo waziwa ngokuthi uMthetho kaRaoult. Lo mthetho uyisisekelo sokuqonda izenzakalo ezahlukahlukene zansuku zonke kanye nezinqubo zezimboni, njengokwenza amakha, ukuhlanzwa kotshwala, kanye nezimiso zokusebenza zokuhluza. Lesi sihloko sizoxoxa ngencazelo yoMthetho kaRaoult, ifomula yawo, izibonelo zokusetshenziswa kwawo, izimo osebenza ngaphansi kwazo, kanye nemikhawulo yawo.
Ukuqonda uMthetho kaRaoult
Umthetho kaRaoult umthetho othi ingcindezi yomhwamuko engaphelele yengxenye esixazululweni esifanele ilingana nengxenye ye-mole yaleyo ngxenye esixazululweni. Lo mthetho wahlongozwa okokuqala yisazi semithi saseFrance, uFrançois-Marie Raoult, ngasekupheleni kwekhulu le-19 ngenkathi efunda izakhiwo zezixazululo.
Kalula nje, uMthetho kaRaoult uyasiza ekuphenduleni umbuzo othi: "Uma i-solvent ixutshwe nenye into, ingcindezi yomhwamuko we-solvent ishintsha kanjani?" Impendulo: ingcindezi yomhwamuko we-solvent izokwehla ngokuya ngesilinganiso se-solvent esikhona engxubeni.
Ifomula Yomthetho KaRaoult
Ukuze uthole ikhambi elifanele eliqukethe izingxenye ezimbili (isibonelo u-A no-B), uMthetho kaRaoult ungabhalwa kanje:
\[
P_A = X_A \cdot P_A^0
\]
Imininingwane:
– \( P_A \) = ingcindezi yomhwamuko engaphelele yengxenye A esixazululweni
– \( X_A \) = ingxenye ye-mole yengxenye A esixazululweni
– \( P_A^0 \) = umfutho womusi wengxenye emsulwa u-A (ekushiseni okufanayo)
Uma esixazululweni kunezingxenye ezimbili eziguquguqukayo (ezihwamuka kalula), khona-ke ingcindezi ephelele yomhwamuko wesisombululo ivezwa kanje:
\[
P_{isamba} = P_A + P_B = X_A \cdot P_A^0 + X_B \cdot P_B^0
\]
Ngakho-ke, ingcindezi ephelele yomhwamuko wesisombululo iyisamba sezingcindezi ezingaphelele zomhwamuko wengxenye ngayinye.
Umqondo Wengxenye Ye-Mole Emthethweni KaRaoult
Ingxenyenamba ye-Mole iyisilinganiso senani lama-moles engxenye nenani eliphelele lama-moles azo zonke izingxenye ezikusisombululo. Ifomula yile:
\[
X_A = \frac{n_A}{n_A + n_B}
\]
Imininingwane:
– \( n_A \) = inani lama-moles engxenye A
– \( n_B \) = inani lama-moles engxenye B
Ingxenyenamba ye-mole ihlala inenani eliphakathi kuka-0 no-1. Uma ingxenyenamba ye-mole yengxenye iphezulu, umnikelo wayo ekucindezelweni komphunga wesisombululo nawo mkhulu.
Isibonelo Sokubalwa Komthetho KaRaoult
Isibonelo, ikhambi lenziwa ngezinto A (i-solvent) kanye ne-B (i-volatile solute). Kuyaziwa ukuthi:
– \( X_A = 0{,}7 \)
– \( P_A^0 = 100 \) mmHg
Khona-ke ingcindezi yomhwamuko engaphelele ka-A esixazululweni yile:
\[
P_A = X_A \cdot P_A^0 = 0{,}7 \cdot 100 = 70 \text{ mmHg}
\]
Lokhu kusho ukuthi umfutho womusi we-solvent A wehla kusuka ku-100 mmHg (uma uhlanzekile) uye ku-70 mmHg ngemva kokuxuba isixazululo.
Uma i-B nayo iguquguqukayo, isibonelo \( X_B = 0{,}3 \) kanye \( P_B^0 = 50 \) mmHg:
\[
P_B = 0{,}3 \cdot 50 = 15 \text{ mmHg}
\]
Ngakho-ke ingcindezi ephelele yomphunga wesisombululo yile:
\[
I-P_{isamba} = 70 + 15 = 85 \umbhalo{ mmHg}
\]
Ubudlelwano Phakathi Komthetho KaRaoult Nokwehla Kokucindezela Komusi
Enye yezindlela ezidumile zokusebenzisa uMthetho kaRaoult ukuchaza ukwehla komfutho womusi lapho i-solute engaguquki ingezwa ku-solvent eguquguqukayo. Ngenxa yokuthi i-solute engaguquki ayifaki isandla ekucindezelweni komusi, umfutho womusi wesisombululo uphansi kunowe-solvent emsulwa.
Empeleni, lapho ubuso besisombululo "bugcwele" izinhlayiya ezincibilikayo, inani lama-molecule e-solvent angaphuma aye esigabeni segesi liyancipha. Ngenxa yalokho, umfutho womusi uyancipha. Lesi simo siyisisekelo sezakhiwo zokuhlangana kwezixazululo, njenge:
- ukwehla komfutho womusi
- ukuphakama kwephuzu lokubila
- ukucindezeleka kwephuzu lokuqandisa
- ingcindezi ye-osmotic
Imibandela Yokusebenzisa Umthetho KaRaoult (Isixazululo Esifanele)
Akuzona zonke izixazululo ezilandela uMthetho kaRaoult ngokuphelele. Lo mthetho usebenza kangcono ezixazululweni ezifanele, okungukuthi izixazululo ezihlangabezana nezimo ezilandelayo:
1. Amandla okukhanga phakathi kwama-molecule afanayo nahlukene cishe afanayo.
Isibonelo, amandla aphakathi kuka-A–A, B–B, kanye no-A–B alingana ngokulingana.
2. Akukho ukusabela kwamakhemikhali okwenzekayo phakathi kwezingxenye ezikusisombululo.
3. Ukuxuba akubangeli izinguquko ezinkulu kuvolumu.
4. Izinga lokushisa elingaguquki (umfutho womusi uncike kakhulu ekushiseni, ngakho-ke izibalo zenziwa ekushiseni okufanayo).
Izibonelo zezixazululo ezibhekana nokufaneleka ngokuvamile ziyizingxube zezinto ezinezakhiwo ezifanayo kanye nama-polarities, isibonelo ezinye izingxube zama-hydrocarbon.
Ukuphambuka eMthethweni kaRaoult
Empeleni, izixazululo eziningi zangempela ziyaphambuka eMthethweni kaRaoult. Lokhu kuphambuka kuhlukaniswe kanje:
1. Ukuphambuka Okuhle
Kwenzeka lapho ingcindezi iyonke yomhwamuko wesisombululo inkulu kunalokho okwabikezelwa uMthetho kaRaoult. Lokhu kusho ukuthi ukusebenzisana phakathi kwama-molecule ahlukene (A–B) kubuthakathaka kunalawo aphakathi kwama-molecule afanayo (A–A noma B–B). Ama-molecule ahwamuka kalula, okwandisa ingcindezi yomhwamuko. Isibonelo esivamile: ingxube ye-ethanol namanzi kwezinye izinto ikhombisa lokhu kuziphatha futhi ingakha i-azeotrope.
2. Ukuphambuka Okubi
Kwenzeka lapho ingcindezi yomhwamuko iyonke ingaphansi kwalokho okubikezelwe nguMthetho kaRaoult. Lokhu kwenzeka lapho amandla akhangayo e-A–B enamandla, ngakho-ke ama-molecule "agcinwa" kakhulu esigabeni soketshezi futhi mancane amathuba okuthi aphele. Isibonelo, ingxube ye-acetone ne-chloroform ibonisa ukuphambuka okungekuhle ngenxa yokusebenzisana okunamandla (isb., izibopho ze-hydrogen).
Indima Yomthetho KaRaoult Ekuhlanjululweni Kwezinto Ezimbiwayo Nasembonini
Umthetho kaRaoult ubalulekile ekwakheni izinqubo zokuhlukanisa izingxube zoketshezi, ikakhulukazi ukucwiliswa. Ukucwiliswa kusebenzisa umehluko ekuguqukeni kwezingxenye. Ngokuqonda ukucindezeleka komhwamuko okungaphelele kwengxenye ngayinye, ososayensi nonjiniyela bangabikezela ukwakheka komhwamuko owakhiwe ngaphezu kwesisombululo.
Izinhlelo zokusebenza zangempela zifaka:
- ukuhlanzwa kotshwala embonini yeziphuzo kanye nemithi
– ukucutshungulwa kwephethiloli ngokusebenzisa ukuhluzwa kwezingxenye
- ukukhiqizwa kwamakha kanye nezinto ezisetshenziswayo ezihlanganisa ingxube yezinto ezishintshashintshayo
- ubunjiniyela bamakhemikhali ekubalweni kokulingana komswakama noketshezi
Ukulinganiselwa koMthetho kaRaoult
Nakuba kuwusizo kakhulu, uMthetho kaRaoult unemikhawulo eminingana, okungukuthi:
– akulona iqiniso ngezixazululo ezinokuxhumana okuqinile (isib. izixazululo ze-electrolyte, izixazululo ezinezibopho ze-hydrogen ezivelele)
- akufaneleki ukugxila okuphezulu kakhulu ezinhlelweni ezingezona ezifanelekile
– ayikwazi ukuchaza ukuziphatha kwezixazululo ezakha ama-azeotropes ngaphandle kwemibono eyengeziwe (isb. ama-coefficients omsebenzi)
Ezimweni eziningi, ososayensi basebenzisa izilungiso ezifana nama-activity coefficients (ku-thermodynamics yesisombululo) ukuze benze izibikezelo zibe nembe kakhudlwana.
Isiphetho
Umthetho kaRaoult uyisimiso esiyisisekelo kumakhemikhali esisombululo esithi ingcindezi engaphelele yomhwamuko wengxenye esixazululweni esifanele ilingana ngqo nengxenye yayo yama-mole. Lo mthetho usenza siqonde ukwehlisa ingcindezi yomhwamuko, sibikezele ingcindezi iyonke yomhwamuko yengxube, futhi sichaze izinqubo ezahlukene zokuhlukanisa ezifana nokuhluzwa. Kodwa-ke, lo mthetho ufaneleka kakhulu ezixazululweni ezifanele futhi ungaphambukiswa ezixazululweni zangempela ngokusebenzisana okunamandla noma okuyinkimbinkimbi kwama-molecule.
Uma ungathanda, ngingasiza futhi ekudaleni inguqulo elula yalesi sihloko yabafundi besikole samabanga aphezulu/esiphakeme, noma inguqulo ejulile enengxoxo ngama-coefficients omsebenzi kanye nama-phase diagram.
