Tauira o ngā Pātai Kōrero mō te Hikohiko Matū
Ko te matū hikohiko he peka o te matū e ako ana i te whanaungatanga i waenga i ngā tauhohenga matū me ngā huringa o te pūngao hiko. I roto i te matū hikohiko, e rua ngā ariā matua: te waikura (te tukunga o ngā irahiko) me te whakaiti (te whiwhi i ngā irahiko). Ka kitea ēnei tukanga i roto i ngā momo pūtau hikohiko e rua: ngā pūtau hikohiko (ngā pūtau hikohiko) me ngā pūtau hikohiko. Kei raro nei ētahi tauira rapanga me ō rātou whakamārama hei āwhina i a koe ki te mārama ki te matū hikohiko.
Tauira Pātai 1: Pūtau Pūngao
Pātai:
Homai he pūtau hiko me ngā irahiko konutea (Zn) me te parahi (Cu) e honoa ana mā te piriti tote. Ka toua te Zn ki roto i te otinga 1 M ZnSO4, ā, ka toua te Cu ki roto i te otinga 1 M CuSO4. Tuhia ngā tauhohenga e puta ana i ia irahiko, ka tatau i te rerekētanga pūmanawa (EMF) o te pūtau hiko. Ngā raraunga pūmanawa hiko paerewa:
\[ E^o_{\text{Zn}^{2+}/\text{Zn}} = -0.76 \, \text{V} \]
\[ E^o_{\text{Cu}^{2+}/\text{Cu}} = +0.34 \, \text{V} \]
Kōrero:
Ko te taahiraa tuatahi ko te whakatau i te tauhohenga redox e puta ana. I roto i te pūtau voltaic, ka puta he tauhohenga redox tūpono i te wāhi e puta ai
– Ka pāngia te konutea (Zn) e te waikura:
\[ \text{Zn (s)} \rightarrow \text{Zn}^{2+} (aq) + 2e^- \]
– Ka whakaitihia te parahi (Cu):
\[ \text{Cu}^{2+} (aq) + 2e^- \rightarrow \text{Cu (s)} \]
Ko te tauhohenga redox katoa i roto i te pūtau voltaic ko:
\[ \text{Zn (s)} + \text{Cu}^{2+} (aq) \rightarrow \text{Zn}^{2+} (aq) + \text{Cu (s)} \]
Muri iho, ka tatauhia e mātou te rerekētanga pūmanawa o te pūtau:
\[ E_{\text{pūtau}} = E^o_{\text{katode}} – E^o_{\text{anode}} \]
Dimana:
– Ko te katote te hikohiko e puta ai te whakaiti (Cu).
– Ko te anode te hikohiko e puta ai te waikura (Zn).
Nō reira,
\[ E_{\text{sel}} = 0.34 \, \text{V} – (-0.76 \, \text{V}) \]
\[ E_{\text{sel}} = 0.34 \, \text{V} + 0.76 \, \text{V} = 1.10 \, \text{V} \]
Ngā tauira:
– Te tauhohenga e puta ana i te anode (Zn):
\[ \text{Zn (s)} \rightarrow \text{Zn}^{2+} (aq) + 2e^- \]
– Ko te tauhohenga e puta ana i te katote (Cu):
\[ \text{Cu}^{2+} (aq) + 2e^- \rightarrow \text{Cu (s)} \]
– Te rerekētanga pūmanawa pūtau (EMF): 1.10 V
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Tauira Pātai 2: Pūtau Hikohiko
Pātai:
I roto i te whakapūtanga hiko o tētahi otinga NaCl, whakahuatia ngā tauhohenga e puta ana i te katote me te anote mēnā ka whakamahia he hiko kore mahi, pērā i te konukawata (Pt). Tātaihia te tapeke utu e hiahiatia ana hei whakaputa i te 1 karamu o te Cl2. (Ar Cl = 35.5)
Kōrero:
Ko te taahiraa tuatahi ko te tuhi i ngā tauhohenga e puta ana i ia irahiko i roto i te otinga tote NaCl.
– I te katote (whakaiti):
I tēnei tukanga, ka whakaitihia ngā iona H+ mai i te wai:
\[ 2H_2O(l) + 2e^- \perematau H_2(g) + 2OH^-(aq) \]
– I te anode (waikura):
Ka waikuratia te ion Cl- kia huri hei hau Cl2:
\[ 2Cl^-(aq) \perematau Cl_2(g) + 2e^- \]
Tauhohenga Katoa:
Nō reira, ko te tauhohenga katoa e puta ana i te electrolysis o te otinga NaCl ko:
\[ 2NaCl(aq) + 2H_2O(l) \perematau 2NaOH(aq) + H_2(g) + Cl_2(g) \]
Hei tatau i te utu e hiahiatia ana hei whakaputa i te 1 karamu o te Cl2, me whakatau tātou i te maha o ngā mole o te Cl2:
\[ \text{Taumaha o Cl}_2 = 1 \text{ karamu} \]
\[ \text{Ar Cl}_2 = 2 \times 35.5 = 71 \text{ karamu/mol} \]
\[ \text{Te maha o ngā mole o Cl}_2 = \frac{1}{71} \text{ mol} \]
I runga i te whārite tauhohenga i te anode, ka puta te 1 mol o te Cl2 mai i te 2 mol o ngā irahiko:
\[ 2Cl^- \rightarrow Cl_2 + 2e^- \]
Ara, e 2 ngā mole o ngā irahiko e hiahiatia ana mō te 1 ira o te Cl2.
Te maha o ngā mole o ngā irahiko:
\[ \text{Tau o ngā mole o ngā irahiko} = 2 \times \frac{1}{71} = \frac{2}{71} \text{ mol} \]
Ka taea te tatau i te utu e hiahiatia ana mā te whakamahi i te uara Faraday (F = 96485 C/mol e^-):
\[ Q = n \whakanuia te F \]
\[ Q = \left(\frac{2}{71} \text{ mol}\right) \times 96485 \text{ C/mol} \]
\[ Q = 2718 \kuputuhi{ C} \]
Ngā tauira:
– Te tauhohenga i te katote:
\[ 2H_2O(l) + 2e^- \perematau H_2(g) + 2OH^-(aq) \]
– Te tauhohenga i te anode:
\[ 2Cl^-(aq) \perematau Cl_2(g) + 2e^- \]
– Ko te tapeke o te utu e hiahiatia ana hei whakaputa i te 1 karamu o te Cl2 he 2718 C.
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Tauira 3: Te Hononga Nernst me ngā Tikanga Kore-Paerewa
Pātai:
Tātaihia te pūmanawa o tētahi pūtau hiko i hangaia mai i ngā irahiko Ag/Ag+ me te kukū o te katote hiriwa o te 0.1 M me ngā irahiko Zn/Zn2+ me te kukū o te 0.01 M. Ko te pūmanawa hiko paerewa ko:
\[ E^o_{\text{Ag}^{+}/\text{Ag}} = +0.80 \, \text{V} \]
\[ E^o_{\text{Zn}^{2+}/\text{Zn}} = -0.76 \, \text{V} \]
Kōrero:
Ko te taahiraa tuatahi ko te tuhi i ngā tauhohenga e puta ana:
– Te waikura i te anode (Zn):
\[ \text{Zn (s)} \rightarrow \text{Zn}^{2+} (aq) + 2e^- \]
– Te whakaiti i te katote (Ag):
\[ \text{Ag}^{+} (aq) + e^- \rightarrow \text{Ag (s)} \]
Tauhohenga katoa:
\[ \text{Zn (s)} + 2\text{Ag}^{+} (aq) \rightarrow \text{Zn}^{2+} (aq) + 2\text{Ag (s)} \]
I runga i te whārite Nernst:
\[ E_{\text{Pūtau}} = E^o_{\text{Pūtau}} – \left( \frac{0.0592}{n} \right) \log \left( \frac{[\text{hua}]}{[\text{tauhohenga}]} \right) \]
Dimana:
\[ n = 2 \]
Tuatahi, tatauhia a E^o_{\text{Sel}}:
\[ E^o_{\text{Sel}} = E^o_{\text{Ag}^{+}/\text{Ag}} – E^o_{\text{Zn}^{2+}/\text{Zn}} \]
\[ E^o_{\text{Sel}} = 0.80 \, \text{V} – (-0.76 \, \text{V}) \]
\[ E^o_{\text{Pūtau}} = 1.56 \, \text{V} \]
Muri iho, tatauhia te pūmanawa pūtau tuturu i te kukū kua hoatu:
\[ E_{\text{Sel}} = 1.56 \, \text{V} – \left( \frac{0.0592}{2} \right) \log \left( \frac{[\text{Zn}^{2+}]}{[\text{Ag}^{+}]^2} \right) \]
\[ E_{\text{Sel}} = 1.56 \, \text{V} – \left( \frac{0.0592}{2} \right) \log \left( \frac{0.01}{(0.1)^2} \right) \]
\[ E_{\text{Pūtau}} = 1.56 \, \text{V} – 0.0296 \log \left( \frac{0.01}{0.01} \right) \]
\[ E_{\text{Pūtau}} = 1.56 \, \text{V} \]
Ngā tauira:
– Ka noho rite tonu ngā tauhohenga e puta ana i te anode me te cathode
– Ko te pūmanawa pūtau me tētahi kukū kua hoatu he 1.56 V
E whakaatu ana tēnei tuhinga me pēhea te whakaoti rapanga i roto i te matū hikohiko, tae atu ki ngā rapanga e pā ana ki ngā pūtau hikohiko, ngā pūtau hikohiko, me ngā tātaitanga mā te whakamahi i te Whārite Nernst. He mea nui te māramatanga hōhonu ki ngā mātāpono kei muri i ngā tauhohenga redox me te kaha ki te whakamahi i ngā raraunga hikohiko hei angitu i roto i te whakaoti rapanga.
