Isibonelo Semibuzo Yengxoxo Ye-Thermochemistry
I-Pendahuluan
I-Thermochemistry iyigatsha le-chemistry elifunda ubudlelwano phakathi kokusabela kwamakhemikhali kanye noshintsho lwamandla, ikakhulukazi ngesimo sokushisa. Kuyisihloko esibalulekile ku-chemistry yemvelo ngoba kusisiza siqonde ukuthi amandla adluliselwa futhi aguqulwa kanjani ngesikhathi sokusabela kwamakhemikhali. Kulesi sihloko, sizoxoxa ngezinkinga eziningana zezibonelo ze-thermochemistry ukusiza ukucacisa le miqondo.
Isibonelo Umbuzo 1: Ushintsho ku-Enthalpy Yokusha
Umbuzo:
I-enthalpy yokushiswa (ΔHc) ye-ethanol (C2H5OH) ingu--1367 kJ/mol. Thola inani lamandla akhishwayo lapho ama-mole amabili e-ethanol eshiswa ngokuphelele!
Ingxoxo:
Ushintsho lwe-enthalpy lokushiswa (ΔHc) amandla akhishwa lapho i-mole eyodwa yento ishiswa ngokuphelele emoyeni. Kwi-ethanol, i-ΔHc = -1367 kJ/mol.
Uma kushiswa ama-moles amabili e-ethanol, inani lamandla akhishwayo yilawa:
\[ \text{Energy release} = 2 \, \text{mol} \times (-1367 \, \text{kJ/mol}) \]
\[ \umbhalo{Amandla okukhipha i-Discharge} = -2734 \, \umbhalo{kJ} \]
Ngakho-ke, uma ama-moles amabili e-ethanol eshiswa ngokuphelele, amandla akhishwayo angama--2734 kJ.
Isibonelo Umbuzo 2: Ukubala i-Reaction Enthalpy kusuka ku-Formation Enthalpy Data
Umbuzo:
Sebenzisa i-enthalpy ejwayelekile elandelayo yedatha yokwakheka ukuze ubale i-enthalpy yokusabela yokwakheka komhwamuko wamanzi:
– \(\Delta H_{\text{f}}^{\circ}(\text{H}_2(g)) = 0 \, \text{kJ/mol}\)
– \(\Delta H_{\text{f}}^{\circ}(\text{O}_2(g)) = 0 \, \text{kJ/mol}\)
– \(\Delta H_{\text{f}}^{\circ}(\text{H}_2\text{O}(g)) = -241.8 \, \text{kJ/mol}\)
Ukusabela:
\[ \text{H}_2(g) + \frac{1}{2}\text{O}_2(g) \rightarrow \text{H}_2\text{O}(g) \]
Ingxoxo:
I-reaction enthalpy (\(\Delta H_{\text{rxn}}\)) ingabalwa kusetshenziswa i-enthalpy ejwayelekile yokwakheka (\(\Delta H_{\text{f}}^{\circ}\)) ngefomula:
\[ \Delta H_{\text{rxn}} = \Sigma \Delta H_{\text{f}}^{\circ} \text{product} – \Sigma \Delta H_{\text{f}}^{\circ} \text{reactants} \]
Ngenxa yalokhu kusabela:
\[ \Delta H_{\text{rxn}} = \Delta H_{\text{f}}^{\circ}(\text{H}_2\text{O}(g)) – \left[ \Delta H_{\text{f}}^{\circ}(\text{H}_2(g)) + \frac{1}{2} \Delta H_{\text{f}}^{\circ}(\text{O}_2(g)) \right] \]
Faka i-enthalpy yenani lokwakheka:
\[ \Delta H_{\text{rxn}} = -241.8 \, \text{kJ/mol} – \left[ 0 + \frac{1}{2} \times 0 \right] \]
\[ \Delta H_{\text{rxn}} = -241.8 \, \text{kJ/mol} \]
Ngakho-ke, i-enthalpy yokusabela ekwakhekeni komhwamuko wamanzi ingu-241.8 kJ/mol.
Isibonelo Umbuzo 3: Umthetho kaHess
Umbuzo:
Nquma ushintsho lwe-enthalpy (\(\Delta H\)) lwempendulo elandelayo:
\[ \text{C(s)} + \frac{1}{2}\text{O}_2(g) \rightarrow \text{CO(g)} \]
Sebenzisa idatha elandelayo:
1. \(\text{C(s)} + \text{O}_2(g) \rightarrow \text{CO}_2(g) \, \Delta H = -393.5 \, \text{kJ}\)
2. \(\text{CO(g)} + \frac{1}{2}\text{O}_2(g) \rightarrow \text{CO}_2(g) \, \Delta H = -283.0 \, \text{kJ}\)
Ingxoxo:
Sebenzisa uMthetho kaHess othi uma ukusabela kwamakhemikhali kungavezwa njengesamba sezinye izindlela eziningana zokusabela, khona-ke ushintsho lwe-enthalpy lokusabela okuphelele luyisamba sezinguquko ze-enthalpy zalezo zindlela zokusabela.
Isinyathelo 1: Bhala ukusabela okudingeka kuguqulwe noma kuguqulwe ukuze kufane nokusabela okuqondiwe:
– Ukusabela (1): \(\text{C(s)} + \text{O}_2(g) \rightarrow \text{CO}_2(g) \, \Delta H = -393.5 \, \text{kJ}\)
– Ukusabela (2): \(\text{CO(g)} + \frac{1}{2}\text{O}_2(g) \rightarrow \text{CO}_2(g) \, \Delta H = -283.0 \, \text{kJ}\)
Isinyathelo 2: Ukusabela okuphambene (2) bese ushintsha uphawu lwe-\(\Delta H\):
\[ \text{CO}_2(g) \rightarrow \text{CO(g)} + \frac{1}{2}\text{O}_2(g) \, \Delta H = 283.0 \, \text{kJ} \]
Isinyathelo 3: Engeza ukusabela (1) kanye nokusabela okubuyiselwe emuva (2):
\[ \text{C(s)} + \text{O}_2(g) \rightarrow \text{CO}_2(g) \, \Delta H = -393.5 \, \text{kJ} \]
\[ \text{CO}_2(g) \rightarrow \text{CO(g)} + \frac{1}{2}\text{O}_2(g) \, \Delta H = 283.0 \, \text{kJ} \]
Isinyathelo 4: Engeza ukusabela okubili:
\[ \text{C(s)} + \text{O}_2(g) + \text{CO}_2(g) \rightarrow \text{CO}_2(g) + \text{CO(g)} + \frac{1}{2}\text{O}_2(g) \]
Ukwenza lula kuphumela ku:
\[ \text{C(s)} + \frac{1}{2} \text{O}_2(g) \rightarrow \text{CO(g)} \]
Ushintsho oluphelele lwe-enthalpy (\(\Delta H\)):
\[ \Delta H = -393.5 \, \text{kJ} + 283.0 \, \text{kJ} = -110.5 \, \text{kJ} \]
Ngakho-ke, ushintsho lwe-enthalpy lokusabela luyi--110.5 kJ.
Isibonelo Umbuzo 4: I-Calorimetry
Umbuzo:
Kuvivinyo lwe-calorimetry, amagremu angu-50 amanzi (c = 4.18 J/g°C) ashiswa kusukela ku-25°C kuya ku-75°C. Bala inani lokushisa (q) elidingekayo.
Ingxoxo:
Inani lokushisa (q) elidingekayo ukuze kufudunyezwe amanzi lingabalwa kusetshenziswa ifomula:
\[ q = m \ cdot c \ cdot \ Delta T \]
– m = isisindo samanzi = 50 g
– c = umthamo wokushisa othize = 4.18 J/g°C
– \(\Delta T = \) ushintsho lokushisa \( = 75°C – 25°C = 50°C \)
\[ q = 50 \, \text{g} \times 4.18 \, \text{J/g°C} \times 50°C \]
\[q = 10450 \, \umbhalo{J} \]
Ngakho-ke, inani lokushisa elidingekayo ukushisa amagremu angu-50 amanzi kusukela ku-25°C kuya ku-75°C lingu-10450 J.
I-Penutup
Ingxoxo yezinkinga eziyisibonelo ezingenhla inikeza umbono oningiliziwe wokuthi imiqondo ye-thermochemical ingasetshenziswa kanjani ukuxazulula izinkinga ezahlukahlukene ezihlobene nokusabela kwamakhemikhali kanye nokuguqulwa kwamandla. I-Thermochemistry ibalulekile emikhakheni ehlukahlukene, okuhlanganisa imboni, amandla, kanye nocwaningo lwesayensi, ngoba isenza sikwazi ukuqonda nokulawula ukuguqulwa kwamandla okwenzeka ekuphenduleni kwamakhemikhali. Ngokuqonda okuhle kwe-thermochemistry, singaklama izinqubo ezisebenza kahle kakhulu futhi sithuthukise ubuchwepheshe obusha, obunobungani nemvelo.
