Ngā Tauira Pātai me te Kōrero mō ngā Whārite Matū Teremā
Ko te matū wera he peka o te matū e ako ana i ngā huringa pūngao e puta ana i roto i ngā tauhohenga matū, inā koa te whakawhiti wera. Kei roto i te matū wera ngā ariā pēnei i te enthalpy, te entropy, me te pūngao kore utu Gibbs, e whakamahia ana hei matapae i te ahunga me te tūponotanga o ngā tauhohenga. I roto i tēnei tuhinga, ka tūhuratia e mātou ētahi tauira raruraru me te matapaki i ngā whārite matū wera.
Ngā Ariā Taketake o te Matū Whakamahana
I mua i te urunga atu ki ngā tauira pātai me te matapaki i aua pātai, he mea nui kia mōhio ki ētahi ariā taketake o te matū wera:
1. Enthalpy (H): Ko te enthalpy he momo pūngao i roto i tētahi pūnaha e inehia ana i raro i ngā āhuatanga pēhanga pumau. Ka taea te whakaatu i te huringa o te enthalpy (\( \Delta H \)) penei:
\[ \Delta H = H_{hua} – H_{kaitautoko} \]
2. Ngā Tauhohenga Endothermic me Exothermic:
– Ko ngā tauhohenga exothermic he tauhohenga e tuku ana i te wera ki te taiao (\( \Delta H < 0 \)). - Ko ngā tauhohenga endothermic he tauhohenga e mimiti ana i te wera mai i te taiao (\( \Delta H > 0 \)).
3. Te Ture a Hess: E ai ki te Ture a Hess, he rite tonu te huringa enthalpy katoa o tētahi tauhohenga matū ahakoa ka puta te tauhohenga i te taahiraa kotahi, i ētahi taahiraa rānei. Ka taea te kī penei:
\[ \Delta H_{katoa} = \Delta H_1 + \Delta H_2 + … + \Delta H_n \]
Ngā Pātai Tauira me te Kōrero
Tauira Pātai 1: Te Tatau i te Huringa Enthalpy
I runga i ngā tauhohenga e whai ake nei:
\[ 2H_2(g) + O_2(g) \perematau 2H_2O(l) \]
Mena e mōhiotia ana ko te huringa enthalpy o te hanganga (\( \Delta H_f \)) o te wai he -285.8 kJ/mol. Tātaihia te huringa enthalpy katoa mō te tauhohenga.
Kōrero:
Ka taea te tatau i te huringa enthalpy o tētahi tauhohenga (\( \Delta H_{tauhohenga} \)) mā te whakamahi i te huringa enthalpy o te hanganga o ngā hua me ngā matū tauhohe.
E mōhiotia ana:
– \[ \Delta H_f(H_2O(l)) = -285.8 \text{ kJ/mol} \]
Nā te mea e rua ngā mole wai ka hangaia, ko te huringa enthalpy katoa o te tauhohenga ko:
\[ \Delta H_{tauhohenga} = 2(-285.8 \text{ kJ/mol}) \]
\[ \Delta H_{tauhohenga} = -571.6 \text{ kJ} \]
Nō reira, ko te huringa enthalpy katoa mō tēnei tauhohenga he -571.6 kJ. He exothermic tēnei tauhohenga nā te mea he kino te \( \Delta H \).
Tauira Pātai 2: Te Whakamahinga o te Ture a Hess
I runga i ngā tauhohenga e whai ake nei:
\[ C(s) + O_2(g) \rightarrow CO_2(g) \hspace{2mm} \text{(1)} \]
\[ C(s) + 1/2 O_2(g) \rightarrow CO(g) \hspace{2mm} \text{(2)} \]
\[ CO(g) + 1/2 O_2(g) \rightarrow CO_2(g) \hspace{2mm} \text{(3)} \]
E mōhiotia ana:
– \(\Delta H_1 = -393.5 \text{ kJ}\)
– \(\Delta H_2 = -110.5 \text{ kJ}\)
Tātaihia te huringa enthalpy mō te tauhohenga (3).
Kōrero:
Whakamahia te Ture a Hess hei whakatau i te huringa enthalpy mō te tauhohenga (3). Kia mōhio koe ka taea te tito i te tauhohenga (3) mai i ngā tauhohenga (1) me (2):
\[ \text{Tauhohenga } (3): CO(g) + 1/2 O_2(g) \rightarrow CO_2(g) \]
Hurihia te tauhohenga (2) hei whakamahi i te Ture a Hess:
\[ CO_2(g) \rightarrow C(s) + O_2(g) \hspace{2mm} \text{(whakamuri 1)}, \Delta H = +393.5 \text{ kJ} \]
\[ C(s) + 1/2 O_2(g) \rightarrow CO(g) \hspace{2mm} \text{(2)}, \Delta H = -110.5 \text{ kJ} \]
Tāpirihia ngā tauhohenga inaianei:
\[ CO_2(g) \rightarrow C(s) + O_2(g) + 1/2 O_2(g) \rightarrow CO(g) + 1/2 O_2(g) \]
\[ CO_2(g) \rightarrow C(s) + O_2(g) \rightarrow CO(g) + 1/2 O_2(g) \]
Tāpirihia ngā huringa enthalpy:
\[ \Delta H_{tauhohenga} = 393.5 – 110.5 \text{ kJ}\]
\[ \Delta H_{tauhohenga} = 283.0 \text{ kJ}\]
Nō reira, mō te tauhohenga \( CO(g) + 1/2 O_2(g) \rightarrow CO_2(g) \), ko te huringa enthalpy he -283.0 kJ.
Tauira Pātai 3: Tauhohenga Calorimeter
Ki te hoatu he 100 mL o te waikawa hauwaiora 1.0 M (HCl) me te 100 mL o te hauwaiora konutai 1.0 M (NaOH). Ina konatunatua ngā mea e rua ki roto i te ine karori, ka piki te pāmahana mai i te 25.0 °C ki te 31.0 °C. Mēnā ko te kaha wera o te wairewa he 4.18 J/g°C, ā, ko te mātotoru o te wairewa he 1.0 g/mL, tatauhia te huringa enthalpy o te whakakorenga.
Kōrero:
Ngā Hipanga:
1. Tātaihia te papatipu o te otinga:
\[ \text{Rōrahi katoa} = 100 \text{ mL} + 100 \text{ mL} = 200 \text{ mL} \]
\[ \text{Pass} = 200 \text{ g} \] (nā te mea ko te mātotoru o te otinga he 1 g/mL)
2. Tātaihia te huringa pāmahana:
\[ \Delta T = 31.0 \text{ °C} – 25.0 \text{ °C} = 6.0 \text{ °C} \]
3. Tātaihia te pūngao e mimitihia ana e te otinga:
\[ q = m \cdot c \cdot \Delta T \]
\[ q = 200 \text{ g} \times 4.18 \text{ J/g°C} \times 6.0 \text{ °C} \]
\[ q = 5016 \kuputuhi{ J} \]
\[ q = 5.016 \text{ kJ} \]
4. Tātaihia te huringa enthalpy:
\[ \Delta H = \frac{q_{\text{solution}}}{\text{mol HCl}} \]
I te mea he ōrite ngā ira o te HCl me te NaOH:
\[ \text{Ngā Ira HCl} = 1.0 \text{ M} \times 0.100 \text{ L} = 0.100 \text{ mol} \]
\[ \Delta H = \frac{5.016 \text{ kJ}}{0.100 \text{ mol}} \]
\[ \Delta H = -50.16 \text{ kJ/mol} \]
Nō reira, ko te huringa enthalpy mō te whakakorenga o te HCl me te NaOH he -50.16 kJ/mol, e tohu ana i tētahi tauhohenga exothermic.
Whakamutunga
He peka nui te matū werawera o te matū e āwhina ana i a tātou ki te mārama ki te hurihanga me te hurihanga o te pūngao i roto i ngā tauhohenga matū. Mā te mārama ki ngā ariā taketake pēnei i te enthalpy me te ture a Hess, me te āhei ki te whakamahi i aua mea ki ngā raruraru mahi, ka taea e tātou te matapae i ngā huringa pūngao e puta ana i roto i ngā tauhohenga matū. Kua whakaatuhia e tēnei tuhinga ētahi tauira raruraru hei āwhina i a koe ki te whakapakari i tō māramatanga ki ngā whārite matū werawera.
