Chitsanzo cha Mafunso Okambirana za Thermochemistry
Pendauluan
Thermochemistry ndi nthambi ya chemistry yomwe imaphunzira ubale womwe ulipo pakati pa zochita za mankhwala ndi kusintha kwa mphamvu, makamaka mu mawonekedwe a kutentha. Ndi mutu wofunikira mu chemistry ya thupi chifukwa umatithandiza kumvetsetsa momwe mphamvu imasamutsidwira ndikusinthidwa panthawi ya zochita za mankhwala. M'nkhaniyi, tikambirana mavuto angapo a zitsanzo za thermochemistry kuti tithandize kumvetsetsa mfundo izi.
Chitsanzo Funso 1: Kusintha kwa Enthalpy ya Kuyaka
Funso:
Mphamvu ya enthalpy ya kuyaka (ΔHc) ya ethanol (C2H5OH) ndi -1367 kJ/mol. Dziwani kuchuluka kwa mphamvu yomwe imatulutsidwa pamene ma mole awiri a ethanol atenthedwa kwathunthu!
Kukambirana:
Kusintha kwa enthalpy kwa kuyaka (ΔHc) ndi mphamvu yomwe imatulutsidwa pamene mole imodzi ya chinthu yatenthedwa kwathunthu mu mpweya. Pa ethanol, ΔHc = -1367 kJ/mol.
Ngati ma mole awiri a ethanol atenthedwa, kuchuluka kwa mphamvu zomwe zimatulutsidwa ndi:
\[ \text{Energy release} = 2 \, \text{mol} \times (-1367 \, \text{kJ/mol}) \]
\[ \text{Discharge energy} = -2734 \, \text{kJ} \]
Choncho, pamene ma mole awiri a ethanol atenthedwa kwathunthu, mphamvu yotulutsidwa ndi -2734 kJ.
Chitsanzo Funso 2: Kuwerengera Reaction Enthalpy kuchokera ku Formation Enthalpy Data
Funso:
Gwiritsani ntchito deta yotsatirayi ya enthalpy yopangira kuti muwerengere momwe enthalpy imagwirira ntchito popanga nthunzi ya madzi:
– \(\Delta H_{\text{f}}^{\circ}(\text{H}_2(g)) = 0 \, \text{kJ/mol}\)
– \(\Delta H_{\text{f}}^{\circ}(\text{O}_2(g)) = 0 \, \text{kJ/mol}\)
– \(\Delta H_{\text{f}}^{\circ}(\text{H}_2\text{O}(g)) = -241.8 \, \text{kJ/mol}\)
Zimene anachita:
\[ \text{H}_2(g) + \frac{1}{2}\text{O}_2(g) \rightarrow \text{H}_2\text{O}(g) \]
Kukambirana:
The reaction enthalpy (\(\Delta H_{\text{rxn}}\)) ikhoza kuwerengedwa pogwiritsa ntchito standard enthalpy of formation (\(\Delta H_{\text{f}}^{\circ}\)) ndi formula:
\[ \Delta H_{\text{rxn}} = \Sigma \Delta H_{\text{f}}^{\circ} \text{product} – \Sigma \Delta H_{\text{f}}^{\circ} \text{reactants} \]
Pa izi:
\[ \Delta H_{\text{rxn}} = \Delta H_{\text{f}}^{\circ}(\text{H}_2\text{O}(g)) – \left[ \Delta H_{\text{f}}^{\circ}(\text{H}_2(g)) + \frac{1}{2} \Delta H_{\text{f}}^{\circ}(\text{O}_2(g)) \right] \]
Lowetsani enthalpy ya mtengo wopangira:
\[ \Delta H_{\text{rxn}} = -241.8 \, \text{kJ/mol} – \left[ 0 + \frac{1}{2} \times 0 \right] \]
\[ \Delta H_{\text{rxn}} = -241.8 \, \text{kJ/mol} \]
Kotero, reaction enthalpy yopangira nthunzi ya madzi ndi -241.8 kJ/mol.
Chitsanzo Funso 3: Lamulo la Hess
Funso:
Dziwani kusintha kwa enthalpy (\(\Delta H\)) pa zomwe zachitika:
\[ \text{C(s)} + \frac{1}{2}\text{O}_2(g) \rightarrow \text{CO(g)} \]
Gwiritsani ntchito deta iyi:
1. \(\text{C(s)} + \text{O}_2(g) \rightarrow \text{CO}_2(g) \, \Delta H = -393.5 \, \text{kJ}\)
2. \(\text{CO(g)} + \frac{1}{2}\text{O}_2(g) \rightarrow \text{CO}_2(g) \, \Delta H = -283.0 \, \text{kJ}\)
Kukambirana:
Gwiritsani ntchito lamulo la Hess lomwe limati ngati reaction ya mankhwala ingafotokozedwe ngati kuchuluka kwa reaction zina zingapo, ndiye kuti kusintha kwa enthalpy kwa reaction yonse ndi kuchuluka kwa kusintha kwa enthalpy kwa reactions zimenezo.
Gawo 1: Lembani zomwe ziyenera kusinthidwa kapena kusinthidwa kuti zigwirizane ndi zomwe zachitika:
– Kachitidwe (1): \(\text{C(s)} + \text{O}_2(g) \rightarrow \text{CO}_2(g) \, \Delta H = -393.5 \, \text{kJ}\)
– Kachitidwe (2): \(\text{CO(g)} + \frac{1}{2}\text{O}_2(g) \rightarrow \text{CO}_2(g) \, \Delta H = -283.0 \, \text{kJ}\)
Gawo 2: Sinthani kusintha (2) ndikusintha chizindikiro cha \(\Delta H\):
\[ \text{CO}_2(g) \rightarrow \text{CO(g)} + \frac{1}{2}\text{O}_2(g) \, \Delta H = 283.0 \, \text{kJ} \]
Gawo 3: Onjezani yankho (1) ndi yankho lobwerera m'mbuyo (2):
\[ \text{C(s)} + \text{O}_2(g) \rightarrow \text{CO}_2(g) \, \Delta H = -393.5 \, \text{kJ} \]
\[ \text{CO}_2(g) \rightarrow \text{CO(g)} + \frac{1}{2}\text{O}_2(g) \, \Delta H = 283.0 \, \text{kJ} \]
Gawo 4: Onjezani mayankho awiri:
\[ \text{C(s)} + \text{O}_2(g) + \text{CO}_2(g) \rightarrow \text{CO}_2(g) + \text{CO(g)} + \frac{1}{2}\text{O}_2(g) \]
Kusavuta kumabweretsa:
\[ \text{C(s)} + \frac{1}{2} \text{O}_2(g) \rightarrow \text{CO(g)} \]
Kusintha konse kwa enthalpy (\(\Delta H\)):
\[ \Delta H = -393.5 \, \text{kJ} + 283.0 \, \text{kJ} = -110.5 \, \text{kJ} \]
Kotero, kusintha kwa enthalpy kwa reaction ndi -110.5 kJ.
Chitsanzo Funso 4: Kuchuluka kwa Kalori
Funso:
Mu kuyesa kwa calorimetry, 50 g ya madzi (c = 4.18 J/g°C) imatenthedwa kuyambira 25°C mpaka 75°C. Werengani kuchuluka kwa kutentha (q) komwe kumafunika.
Kukambirana:
Kuchuluka kwa kutentha (q) komwe kumafunika kuti madzi atenthedwe kumatha kuwerengedwa pogwiritsa ntchito fomula iyi:
\[ q = m \cdot c \cdot \Delta T \]
– m = kulemera kwa madzi = 50 g
– c = mphamvu yeniyeni ya kutentha = 4.18 J/g°C
– \(\Delta T = \) kusintha kwa kutentha \( = 75°C – 25°C = 50°C \)
\[ q = 50 \, \text{g} \times 4.18 \, \text{J/g°C} \times 50°C \]
\[q = 10450 \, \malemba{J} \]
Choncho, kuchuluka kwa kutentha komwe kumafunika kuti 50 g ya madzi itenthedwe kuyambira 25°C mpaka 75°C ndi 10450 J.
Kutseka
Kukambirana za mavuto omwe ali pamwambapa kumapereka chithunzithunzi chatsatanetsatane cha momwe malingaliro a thermochemical angagwiritsidwire ntchito pothetsa mavuto osiyanasiyana okhudzana ndi kusintha kwa mankhwala ndi kusintha kwa mphamvu. Thermochemistry ndi yofunika kwambiri m'magawo osiyanasiyana, kuphatikizapo mafakitale, mphamvu, ndi kafukufuku wasayansi, chifukwa imatithandiza kumvetsetsa ndikusintha kusintha kwa mphamvu komwe kumachitika mu kusintha kwa mankhwala. Tikamvetsetsa bwino za thermochemistry, titha kupanga njira zogwira mtima kwambiri ndikupanga ukadaulo watsopano komanso wosamala chilengedwe.
