Lipotso tsa Mehlala le Puisano ea Litekanyo tsa Thermochemical
Thermochemistry ke lekala la k'hemistri le ithutang diphetoho tsa matla tse hlahang nakong ya diketso tsa dikhemikhale, haholoholo phetiso ya mocheso. Thermochemistry e kenyelletsa mehopolo e kang enthalpy, entropy, le Gibbs free energy, tse sebediswang ho bolela esale pele tataiso le ho iketsahalla ha diketso. Sehloohong sena, re tla hlahloba mathata a mmalwa a mehlala mme re buisane ka di-equation tsa thermochemical.
Mehopolo ea Motheo ea Thermochemistry
Pele o kena lipotsong tsa mohlala le puisanong ea tsona, ho bohlokoa ho tseba likhopolo tse ling tsa motheo tsa thermochemistry:
1. Enthalpy (H): Enthalpy ke mofuta oa matla tsamaisong e lekanngoang tlas'a maemo a khatello e sa khaotseng. Phetoho ea enthalpy (\( \Delta H \)) e ka hlalosoa ka tsela ena:
\[ \Delta H = H_{sehlahisoa} – H_{reactant} \]
2. Likarabelo tsa Endothermic le Exothermic:
– Dikarabelo tsa Exothermic ke dikarabelo tse lokollang mocheso tikolohong (\( \Delta H < 0 \)). - Dikarabelo tsa Endothermic ke dikarabelo tse monyang mocheso tikolohong (\( \Delta H > 0 \)).
3. Molao oa Hess: Molao oa Hess o re phetoho e felletseng ea enthalpy ea karabelo ea lik'hemik'hale e tšoana ho sa tsotelehe hore na karabelo e etsahala mohatong o le mong kapa mehatong e 'maloa. E ka boleloa ka tsela ena:
\[ \Delta H_{total} = \Delta H_1 + \Delta H_2 + … + \Delta H_n \]
Lipotso tsa Mehlala le Puisano
Mohlala oa Potso ea 1: Ho Bala Phetoho ea Enthalpy
Ka lebaka la karabelo e latelang:
\[ 2H_2(g) + O_2(g) \ motsu 2H_2O(l) \]
Haeba ho tsebahala hore phetoho ea enthalpy ea sebopeho (\( \Delta H_f \)) ea metsi ke -285.8 kJ/mol. Bala phetoho eohle ea enthalpy bakeng sa karabelo.
Puisano:
Phetoho ea enthalpy ea karabelo (\( \Delta H_{reaction} \)) e ka baloa ho sebelisoa phetoho ea enthalpy ea ho thehoa ha lihlahisoa le li-reactant.
Hoa tsebahala:
– \[ \Delta H_f(H_2O(l)) = -285.8 \text{ kJ/mol} \]
Kaha ho thehoa limole tse peli tsa metsi, phetoho e felletseng ea karabelo ea enthalpy ke:
\[ \Delta H_{reaction} = 2(-285.8 \text{kJ/mol}) \]
\[ \Delta H_{reaction} = -571.6 \text{kJ} \]
Kahoo, phetoho e felletseng ea enthalpy bakeng sa karabelo ena ke -571.6 kJ. Karabelo ena ke ea exothermic hobane \( \Delta H \) ha e na thuso.
Mohlala oa Potso ea 2: Tšebeliso ea Molao oa Hess
Ka lebaka la karabelo e latelang:
\[ C(s) + O_2(g) \rightarrow CO_2(g) \hspace{2mm} \text{(1)} \]
\[ C(s) + 1/2 O_2(g) \motsu o nepahetseng CO(g) \hspace{2mm} \text{(2)} \]
\[ CO(g) + 1/2 O_2(g) \motsu o nepahetseng CO_2(g) \hspace{2mm} \text{(3)} \]
Hoa tsebahala:
– \(\Delta H_1 = -393.5 \mongolo{kJ}\)
– \(\Delta H_2 = -110.5 \mongolo{kJ}\)
Bala phetoho ea enthalpy bakeng sa karabelo (3).
Puisano:
Sebelisa Molao oa Hess ho fumana phetoho ea enthalpy bakeng sa karabelo (3). Hlokomela hore karabelo (3) e ka etsoa ka liketso (1) le (2):
\[ \text{Reaction } (3): CO(g) + 1/2 O_2(g) \motsu o nepahetseng CO_2(g) \]
Fetolela karabelo (2) ho sebelisa Molao oa Hess:
\[ CO_2(g) \motsu o nepahetseng C(s) + O_2(g) \hspace{2mm} \text{(inverse 1)}, \Delta H = +393.5 \text{kJ} \]
\[ C(s) + 1/2 O_2(g) \motsu o nepahetseng CO(g) \hspace{2mm} \text{(2)}, \Delta H = -110.5 \text{kJ} \]
Jwale eketsa dikarabelo:
\[ CO_2(g) \motsu o nepahetseng C(s) + O_2(g) + 1/2 O_2(g) \motsu o nepahetseng CO(g) + 1/2 O_2(g) \]
\[ CO_2(g) \motsu o nepahetseng C(s) + O_2(g) \motsu o nepahetseng CO(g) + 1/2 O_2(g) \]
Eketsa liphetoho tsa enthalpy:
\[ \Delta H_{reaction} = 393.5 – 110.5 \text{kJ}\]
\[ \Delta H_{reaction} = 283.0 \text{kJ}\]
Kahoo, bakeng sa karabelo \( CO(g) + 1/2 O_2(g) \rightarrow CO_2(g) \), phetoho ea enthalpy ke -283.0 kJ.
Mohlala oa Potso ea 3: Karabelo ea Calorimeter
Ha ho fanoe ka 100 mL ea 1.0 M hydrochloric acid (HCl) le 100 mL ea 1.0 M sodium hydroxide (NaOH). Ha tse peli li kopantsoe ka har'a calorimeter, mocheso o eketseha ho tloha ho 25.0 °C ho isa ho 31.0 °C. Haeba matla a mocheso a tharollo ea metsi e le 4.18 J/g°C 'me bongata ba tharollo e le 1.0 g/mL, bala phetoho ea enthalpy ea neutralization.
Puisano:
Langkah-langkah:
1. Bala boima ba tharollo:
\[ \text{Bophahamo bohle} = 100 \text{mL} + 100 \text{mL} = 200 \text{mL} \]
\[ \text{Mass} = 200 \text{g} \] (hobane bongata ba tharollo ke 1 g/mL)
2. Bala phetoho ea mocheso:
\[ \Delta T = 31.0 \mongolo{ °C} – 25.0 \mongolo{ °C} = 6.0 \mongolo{ °C} \]
3. Bala matla a monngoang ke tharollo:
\[ q = m \cdot c \cdot \Delta T \]
\[q = 200 \mongolo{g} \nako 4.18 \mongolo{J/g°C} \nako 6.0 \mongolo{°C} \]
\[q = 5016 \mongolo{J} \]
\[q = 5.016 \mongolo{kJ} \]
4. Bala phetoho ea enthalpy:
\[ \Delta H = \frac{q_{\text{solution}}}{\text{mol HCl}} \]
Ha re nahana hore li-moles tsa HCl le NaOH lia tšoana:
\[ \text{Moles HCl} = 1.0 \text{ M} \times 0.100 \text{ L} = 0.100 \text{ mol} \]
\[ \Delta H = \frac{5.016 \text{ kJ}}{0.100 \text{ mol}} \]
\[ \Delta H = -50.16 \mongolo{ kJ/mol} \]
Ka hona, phetoho ea enthalpy bakeng sa ho se neutralization ea HCl le NaOH ke -50.16 kJ/mol, e leng se bontšang karabelo ea exothermic.
Qetello
Thermochemistry ke lekala la bohlokoa la k'hemistri le re thusang ho utloisisa hore na matla a fetoloa le ho fetoloa joang liketsong tsa lik'hemik'hale. Ka ho utloisisa likhopolo tsa motheo tse kang enthalpy le molao oa Hess, le ho khona ho li sebelisa mathateng a sebetsang, re ka bolela esale pele liphetoho tsa matla tse hlahang liketsong tse fapaneng tsa lik'hemik'hale. Sengoloa sena se hlahisitse mehlala e 'maloa ea mathata ao ka tšepo a tla thusa ho matlafatsa kutloisiso ea hau ea li-equation tsa thermochemical.
