Mohlala oa Lipotso tsa Puisano ea Thermochemistry
Pendahuluan
Thermochemistry ke lekala la k'hemistri le ithutang kamano pakeng tsa diketso tsa dikhemikhale le diphetoho tsa matla, haholo-holo ka mokgwa wa mocheso. Ke sehlooho sa bohlokwa k'hemistring ya mmele hobane se re thusa ho utlwisisa hore na matla a fetisetswa le ho fetolwa jwang nakong ya diketso tsa dikhemikhale. Sehloohong sena, re tla buisana ka mathata a mmalwa a mehlala ya k'hemistri ho thusa ho hlakisa dikgopolo tsena.
Mohlala oa Potso ea 1: Phetoho ea Enthalpy ea ho Chesa
Potso:
Enthalpy ea ho chesa (ΔHc) ea ethanol (C2H5OH) ke -1367 kJ/mol. Fumana hore na ke matla a makae a lokolloang ha limole tse 2 tsa ethanol li chesoa ka botlalo!
Puisano:
Phetoho ea enthalpy ea ho tuka (ΔHc) ke matla a lokolloang ha mole e le 'ngoe ea ntho e chesoa ka botlalo ka oksijene. Bakeng sa ethanol, ΔHc = -1367 kJ/mol.
Haeba limole tse peli tsa ethanol li chesoa, matla a lokolloang ke:
\[ \text{Energy release} = 2 \, \text{mol} \times (-1367 \, \text{kJ/mol}) \]
\[ \text{Discharge energy} = -2734 \, \text{kJ} \]
Kahoo, ha limole tse 2 tsa ethanol li chesoa ka botlalo, matla a lokolloang ke -2734 kJ.
Mohlala Potso ea 2: Ho Bala Reaction Enthalpy ho tsoa ho Formation Enthalpy Data
Potso:
Sebelisa enthalpy e tloaelehileng e latelang ea data ea sebopeho ho bala karabelo ea enthalpy ea sebopeho sa mouoane oa metsi:
– \(\Delta H_{\text{f}}^{\circ}(\text{H}_2(g)) = 0 \, \text{kJ/mol}\)
– \(\Delta H_{\text{f}}^{\circ}(\text{O}_2(g)) = 0 \, \text{kJ/mol}\)
– \(\Delta H_{\text{f}}^{\circ}(\text{H}_2\text{O}(g)) = -241.8 \, \text{kJ/mol}\)
Karabelo:
\[ \text{H}_2(g) + \frac{1}{2}\text{O}_2(g) \rightarrow \text{H}_2\text{O}(g) \]
Puisano:
Karabo ea enthalpy (\(\Delta H_{\text{rxn}}\)) e ka baloa ho sebelisoa enthalpy e tloaelehileng ea sebopeho (\(\Delta H_{\text{f}}^{\circ}\)) ka foromo:
\[ \Delta H_{\text{rxn}} = \Sigma \Delta H_{\text{f}}^{\circ} \text{product} – \Sigma \Delta H_{\text{f}}^{\circ} \text{reactants} \]
Bakeng sa karabelo ena:
\[ \Delta H_{\text{rxn}} = \Delta H_{\text{f}}^{\circ}(\text{H}_2\text{O}(g)) – \left[ \Delta H_{\text{f}}^{\circ}(\text{H}_2(g)) + \frac{1}{2} \Delta H_{\text{f}}^{\circ}(\text{O}_2(g)) \right] \]
Kenya enthalpy ea boleng ba sebopeho:
\[ \Delta H_{\text{rxn}} = -241.8 \, \text{kJ/mol} – \left[ 0 + \frac{1}{2} \times 0 \right] \]
\[ \Delta H_{\text{rxn}} = -241.8 \, \text{kJ/mol} \]
Kahoo, karabelo ea enthalpy bakeng sa ho thehoa ha mouoane oa metsi ke -241.8 kJ/mol.
Mohlala oa Potso ea 3: Molao oa Hess
Potso:
Fumana phetoho ea enthalpy (\(\Delta H\)) bakeng sa karabelo e latelang:
\[ \text{C(s)} + \frac{1}{2}\text{O}_2(g) \rightarrow \text{CO(g)} \]
Sebelisa lintlha tse latelang:
1. \(\text{C(s)} + \text{O}_2(g) \rightarrow \text{CO}_2(g) \, \Delta H = -393.5 \, \text{kJ}\)
2. \(\text{CO(g)} + \frac{1}{2}\text{O}_2(g) \rightarrow \text{CO}_2(g) \, \Delta H = -283.0 \, \text{kJ}\)
Puisano:
Sebelisa Molao oa Hess o bolelang hore haeba karabelo ea lik'hemik'hale e ka hlahisoa e le kakaretso ea likarabelo tse ling tse 'maloa, joale phetoho ea enthalpy ea karabelo ka kakaretso ke kakaretso ea liphetoho tsa enthalpy tsa likarabelo tseo.
Mohato oa 1: Ngola karabelo e hlokang ho fetoloa kapa ho fetoloa ho tsamaisana le karabelo e reretsoeng:
– Karabelo (1): \(\text{C(s)} + \text{O}_2(g) \rightarrow \text{CO}_2(g) \, \Delta H = -393.5 \, \text{kJ}\)
– Karabelo (2): \(\text{CO(g)} + \frac{1}{2}\text{O}_2(g) \rightarrow \text{CO}_2(g) \, \Delta H = -283.0 \, \text{kJ}\)
Mohato oa 2: Reverse reaction (2) 'me u fetole letšoao la \(\Delta H\):
\[ \text{CO}_2(g) \rightarrow \text{CO(g)} + \frac{1}{2}\text{O}_2(g) \, \Delta H = 283.0 \, \text{kJ} \]
Mohato oa 3: Kenya karabelo (1) le karabelo e khutlisitsoeng morao (2):
\[ \text{C(s)} + \text{O}_2(g) \rightarrow \text{CO}_2(g) \, \Delta H = -393.5 \, \text{kJ} \]
\[ \text{CO}_2(g) \rightarrow \text{CO(g)} + \frac{1}{2}\text{O}_2(g) \, \Delta H = 283.0 \, \text{kJ} \]
Mohato oa 4: Eketsa likarabelo tse peli:
\[ \text{C(s)} + \text{O}_2(g) + \text{CO}_2(g) \rightarrow \text{CO}_2(g) + \text{CO(g)} + \frac{1}{2}\text{O}_2(g) \]
Ho nolofatsa lintho ho fella ka:
\[ \text{C(s)} + \frac{1}{2} \text{O}_2(g) \rightarrow \text{CO(g)} \]
Phetoho e felletseng ea enthalpy (\(\Delta H\)):
\[ \Delta H = -393.5 \, \mongolo{kJ} + 283.0 \, \mongolo{kJ} = -110.5 \, \mongolo{kJ} \]
Kahoo, phetoho ea enthalpy bakeng sa karabelo ke -110.5 kJ.
Mohlala oa Potso ea 4: Khalorimetry
Potso:
Tekong ea calorimetry, 50 g ea metsi (c = 4.18 J/g°C) e futhumatsoa ho tloha ho 25°C ho isa ho 75°C. Bala tekanyo ea mocheso (q) o hlokahalang.
Puisano:
Palo ea mocheso (q) e hlokahalang ho futhumatsa metsi e ka baloa ho sebelisoa foromo:
\[ q = m \cdot c \cdot \Delta T \]
– m = boima ba metsi = 50 g
– c = bokgoni bo itseng ba mocheso = 4.18 J/g°C
– \(\Delta T = \) phetoho mochesong \( = 75°C – 25°C = 50°C \)
\[q = 50 \, \text{g} \times 4.18 \, \text{J/g°C} \times 50°C \]
\[q = 10450 \, \mongolo{J} \]
Kahoo, mocheso o hlokahalang ho futhumatsa 50 g ea metsi ho tloha ho 25°C ho isa ho 75°C ke 10450 J.
Ho koala
Puisano ea mathata a mohlala a kaholimo e fana ka kakaretso e qaqileng ea kamoo likhopolo tsa thermochemical li ka sebelisoang ho rarolla mathata a fapaneng a amanang le likarabelo tsa lik'hemik'hale le liphetoho tsa matla. Thermochemistry e bohlokoa haholo mafapheng a fapaneng, ho kenyeletsoa indasteri, matla le lipatlisiso tsa mahlale, hobane e re lumella ho utloisisa le ho laola liphetoho tsa matla tse hlahang likarabelong tsa lik'hemik'hale. Ka kutloisiso e ntle ea thermochemistry, re ka rala lits'ebetso tse sebetsang hantle le ho nts'etsapele mahlale a macha, a mosa haholo tikolohong.
