Nā Nīnau Laʻana a me ke Kūkākūkā ʻana o nā Noi Electrochemical
ʻO ka electrochemistry kahi lālā o ke kemika e aʻo ana i ka pilina ma waena o nā hopena kemika a me ka uila. I ke ola o kēlā me kēia lā, hiki ke loaʻa ka electrochemistry ma nā ʻano like ʻole, e like me nā pila, nā mea ʻike, ka pala, a me nā kaʻina hana electroplating. No ka hoʻomaopopo hou aku i kēia, hōʻike mākou i kekahi mau pilikia hoʻohālike a me nā kūkākūkā e pili ana i nā noi electrochemistry.
Laʻana Nīnau 1: Pākahi Galvanic (Pūnaewele Voltaic)
Nīnau:
Hana ʻia kahi cell galvanic me nā electrodes Zn (zinc) a me Cu (keleawe) i hoʻoluʻu ʻia i loko o nā hopena ZnSO₄ a me CuSO₄. ʻO ka potential electrode maʻamau no Zn²⁺/Zn he -0,76 V, a no Cu²⁺/Cu he +0,34 V. E helu i ka voltage cell (E° cell) o ka cell galvanic.
Kūkākūkā:
1. E hoʻoholo i ka hopena o ka hapalua o ke kelepona:
– Ka hopena hapalua-kelepona no ka zinc (Zn):
\[
Zn \rightarrow Zn^{2+} + 2e^-
\]
– Ka hopena hapalua-kelepona no ke keleawe (Cu):
\[
Cu^{2+} + 2e^- \rightarrow Cu
\]
2. Ke ʻike ʻana i ka Anode a me ka Cathode:
– Anode (oxidation): Zn → Zn²⁺ + 2e⁻ (ʻoi aku ka maikaʻi ʻole, -0.76 V)
– Cathode (hōʻemi): Cu²⁺ + 2e⁻ → Cu (ʻoi aku ka maikaʻi, +0.34 V)
3. Ke helu ʻana i ke anakahi uila o ke kelepona (E° kelepona):
– ʻO ke ʻano uila maʻamau o ke kelepona:
\[
E°_{\text{cell}} = E°_{\text{cathode}} – E°_{\text{anode}}
\]
Me:
\[
E°_{\text{cathode}} = +0,34 \text{ V}
\]
\[
E°_{\text{anode}} = -0,76 \text{ V}
\]
– No laila, ke ana uila o ke kelepona:
\[
E°_{\text{sel}} = 0.34 \text{ V} – (-0.76 \text{ V}) = 1.10 \text{ V}
\]
Laʻana Nīnau 2: Electrolysis o ka NaCl Solution
Nīnau:
I ka electrolysis o kahi hopena NaCl (aq) me ka hoʻohana ʻana i nā electrodes inert, e hoʻoholo i nā kinoea i hana ʻia ma ka anode a me ka cathode. Eia kekahi, e kākau i lalo i nā hopena e hana ʻia ma kēlā me kēia electrode.
Kūkākūkā:
1. Ka Hana ma ka Electrode:
– Cathode (Hoʻemi):
ʻO nā iona e pili ana paha ʻo Na⁺ a me H₂O.
ʻO nā hopena hōʻemi e hana pinepine ʻia:
\[
2H_2O + 2e^- \arrow H_2 (g) + 2OH^-
\]
No laila, ʻo ke kinoea i hana ʻia ma ka cathode ʻo \(H_2 \).
– Anode (ʻOkika):
ʻO nā iona e pili ana paha, ʻo ia ʻo Cl⁻ a me H₂O.
ʻO nā hopena oxidation e hana pinepine ʻia:
\[
2Cl^- Cl_2 (g) + 2e^-
\]
No laila, ʻo ke kinoea i hana ʻia ma ka anode ʻo \(Cl_2 \).
2. Ka Manaʻo Holoʻokoʻa:
– Ka pane ʻana ma ke cathode:
\[
2H_2O + 2e^- \arrow H_2 (g) + 2OH^-
\]
– Ka pane ʻana ma ka anode:
\[
2Cl^- Cl_2 (g) + 2e^-
\]
– Ka hopena holoʻokoʻa:
\[
2H_2O + 2Cl^- \arrow H_2 (g) + Cl_2 (g) + 2OH^-
\]
Laʻana Nīnau 3: Kaʻina Hana Electroplating
Nīnau:
E helu i ka nuipa o ke kālā (Ag) i waiho ʻia ma luna o ke cathode ma ka hoʻopili ʻana i kahi au uila o 0,5 A no 2 mau hola i loko o kahi hopena AgNO₃. ʻO ka nuipa molar o ke kālā he 107,87 g/mol a ʻo 1 Faraday ua like ia me 96.485 C/mol e⁻.
Kūkākūkā:
1. E hoʻoholo i ka huina o ka uku uila (Q):
– Au (I) = 0.5 A
– Manawa (t) = 2 hola = 2 × 3600 kekona = 7200 kekona
– Ua helu ʻia ka huina o ka uku uila (Q) me ka hoʻohana ʻana i ke ʻano hana:
\[
Q = I \times t
\]
- No laila:
\[
Q = 0.5 \text{ A} \times 7200 \text{ s} = 3600 \text{ C}
\]
2. Ke helu ʻana i ka helu o nā mole o nā electrons (n):
– 1 mole o nā electrons = 96.485 C
– Ka helu o nā mole o nā electrons i hāʻawi ʻia:
\[
n = \frac{3600 \text{ C}}{96.485 \text{ C/mol}} \approx 0.0373 \text{ mol}
\]
3. Ke hoʻoholo nei i ka nui o ke kālā i waiho ʻia:
– Ka hopena hōʻemi ma ke cathode:
\[
Ag^+ + e^- \rightarrow Ag \text{ (s)}
\]
– Hoʻopuka ka 1 mole o nā electrons i 1 mole o Ag
– Ka helu o nā mole o Ag i waiho ʻia:
\[
0.0373 \text{ mol Ag}
\]
– Ke hoʻohana nei i ka nuipa molar o Ag (107,87 g/mol):
\[
Ka nui o Ag = 0.0373 mol times 107.87 g/mol approx 4.02 g
\]
No laila, ʻo ke kaumaha o ke kālā i waiho ʻia ma luna o ke cathode ma kahi o 4.02 grams.
Laʻana Nīnau 4: Ka ʻAi ʻana
Nīnau:
E wehewehe i ke kaʻina hana pala o ka hao i loko o kahi kaiapuni pulu a kākau i lalo i nā hopena kemika e hana ʻia ana.
Kūkākūkā:
1. Nā Pae ʻAi ʻino:
– Ka pane ma ka Anode:
Hoʻopili ʻia ka hao i nā iona ferric:
\[
ʻO Fe \rightarrow Fe^{2+} + 2e^-
\]
– Ka pane ma ke Cathode:
Hoʻopili ka oxygen i ka lewa me ka wai a me nā electrons mai ka anode:
\[
ʻO_2 + 4H^+ + 4e^- \rightarrow 2H_2O
\]
I loko o kahi kaiapuni neutral-non-acidic, ʻo ka hopena kūpono loa:
\[
O_2 + 2H_2O + 4e^- \rightarrow 4OH^-
\]
2. Ka hoʻokumu ʻia ʻana o ka Iron Hydroxide:
– Hoʻohui nā iona Fe²⁺ me nā iona OH⁻ e hana i ka Fe(OH)₂:
\[
Fe^{2+} + 2OH^- \rightarrow Fe(OH)_2
\]
3. Ka Hoʻokumu ʻia ʻana o ka ʻUlu:
– ʻO ka hoʻonui ʻana i ka oxidation o Fe(OH)₂ e hana i ka Fe(OH)₃ e maloʻo ana a hana i ka ʻōpala (Fe₂O₃.nH₂O):
\[
4Fe(OH)_2 + O_2 + 2H_2O \ 4Fe(OH)_3
\]
– Hiki iā Fe(OH)₃ ke hoʻololi i Fe₂O₃ ma ka nalowale ʻana o ka wai:
\[
2Fe(OH)_3 \rightarrow Fe_2O_3 + 3H_2O
\]
Hōʻike kēia kaʻina hana pehea e pala ai ka hao ma o kahi moʻo o nā hopena electrochemical. He mea nui ka ʻike o ka pala no ka mālama ʻana i ke kūpaʻa o nā mea metala i loko o nā hale a me nā ʻoihana.
Ma ka hoʻomaopopo ʻana i nā nīnau hoʻohālike a me nā kūkākūkā ma luna, ua manaʻolana ʻia e hiki i ka poʻe heluhelu ke loaʻa i kahi kiʻi maopopo o ka hoʻopili pono ʻana o nā loina electrochemical i ke ola o kēlā me kēia lā.
