Chitsanzo cha Mafunso Okambirana za Electrochemistry
Electrochemistry ndi nthambi ya chemistry yomwe imaphunzira ubale womwe ulipo pakati pa zochita za mankhwala ndi kusintha kwa mphamvu zamagetsi. Mu electrochemistry, pali mfundo zazikulu ziwiri: okosijeni (kutulutsidwa kwa ma elekitironi) ndi kuchepetsa (kuchuluka kwa ma elekitironi). Njirazi zitha kuwonedwa m'mitundu iwiri ya maselo a electrochemical: maselo a voltaic (maselo a galvanic) ndi maselo a electrolytic. Pansipa pali zitsanzo za mavuto ndi mafotokozedwe awo kuti akuthandizeni kumvetsetsa electrochemistry.
Chitsanzo Funso 1: Selo ya Voltaic
Funso:
Popeza pali selo ya voltaic yokhala ndi ma electrode a zinc (Zn) ndi mkuwa (Cu) olumikizidwa kudzera mu mlatho wamchere. Zn imaviikidwa mu yankho la 1 M ZnSO4 ndipo Cu imaviikidwa mu yankho la 1 M CuSO4. Lembani zomwe zimachitika pa electrode iliyonse ndikuwerengera kusiyana kwa potential (EMF) ya selo ya voltaic. Deta yokhazikika ya electrode potential:
\[ E^o_{\text{Zn}^{2+}/\text{Zn}} = -0.76 \, \text{V} \]
\[ E^o_{\mawu{Cu}^{2+}/\mawu{Cu}} = +0.34 \, \mawu{V} \]
Kukambirana:
Gawo loyamba ndikudziwa momwe redox imachitikira. Mu selo ya voltaic, redox yodzidzimutsa imachitika pomwe
– Zinc (Zn) imalowa mu okosijeni:
\[ \text{Zn (s)} \rightarrow \text{Zn}^{2+} (aq) + 2e^- \]
– Mkuwa (Cu) umachepetsedwa:
\[ \zolemba{Cu}^{2+} (aq) + 2e^- \zolemba zamanja{Cu (s)} \]
Chiwerengero chonse cha redox mu selo ya voltaic ndi:
\[ \text{Zn (s)} + \text{Cu}^{2+} (aq) \rightarrow \text{Zn}^{2+} (aq) + \text{Cu (s)} \]
Kenako, tidzawerengera kusiyana kwa kuthekera kwa maselo:
\[ E_{\text{cell}} = E^o_{\text{cathode}} – E^o_{\text{anode}} \]
Kumene:
– Cathode ndi electrode komwe kuchepetsa (Cu) kumachitika.
– Anode ndi electrode komwe kumapezeka okosijeni (Zn).
Ndicholinga choti,
\[ E_{\text{sel}} = 0.34 \, \text{V} – (-0.76 \, \text{V}) \]
\[ E_{\text{sel}} = 0.34 \, \text{V} + 0.76 \, \text{V} = 1.10 \, \text{V} \]
Pomaliza:
– Zomwe zimachitika pa anode (Zn):
\[ \text{Zn (s)} \rightarrow \text{Zn}^{2+} (aq) + 2e^- \]
– Zomwe zimachitika pa cathode (Cu):
\[ \zolemba{Cu}^{2+} (aq) + 2e^- \zolemba zamanja{Cu (s)} \]
– Kusiyana kwa mphamvu ya maselo (EMF): 1.10 V
-
Chitsanzo Funso 2: Selo ya Electrolytic
Funso:
Mu electrolysis ya yankho la NaCl, tchulani zomwe zimachitika pa cathode ndi anode ngati electrode yopanda mphamvu, monga platinamu (Pt), yagwiritsidwa ntchito. Werengani ndalama zonse zomwe zimafunika kuti mupange gramu imodzi ya Cl2. (Ar Cl = 35.5)
Kukambirana:
Gawo loyamba ndikulemba zomwe zimachitika pa electrode iliyonse mu yankho la mchere wa NaCl.
– Pa cathode (kuchepetsa):
Mu njira iyi, ma H+ ion ochokera m'madzi adzachepetsedwa:
\[ 2H_2O(l) + 2e^- \muvi wa kumanja H_2(g) + 2OH^-(aq) \]
- Pa anode (oxidation):
Cl-ion idzasinthidwa kukhala mpweya wa Cl2:
\[ 2Cl^-(aq) \movina Cl_2(g) + 2e^- \]
Zonse Zomwe Zachitika:
Kotero, zonse zomwe zimachitika mu electrolysis ya NaCl solution ndi:
\[ 2NaCl(aq) + 2H_2O(l) \muvi 2NaOH(aq) + H_2(g) + Cl_2(g) \]
Kuti tiwerengere mtengo wofunikira kuti tipeze gramu imodzi ya Cl2, tifunika kudziwa kuchuluka kwa ma moles a Cl2:
\[ \text{Misa ya Cl}_2 = 1 \text{gram} \]
\[ \text{Ar Cl}_2 = 2 \times 35.5 = 71 \text{ gram/mol} \]
\[ \text{Chiwerengero cha ma moles a Cl}_2 = \frac{1}{71} \text{ mol} \]
Kutengera ndi equation ya reaction pa anode, 1 mol ya Cl2 imapangidwa kuchokera ku 2 mol ya ma electron:
\[ 2Cl^- \rightarrow Cl_2 + 2e^- \]
Mwa kuyankhula kwina, mole imodzi ya Cl2 imafuna ma mole awiri a ma elekitironi.
Chiwerengero cha ma moles a ma elekitironi:
\[ \text{Number of moles of electrons} = 2 \times \frac{1}{71} = \frac{2}{71} \text{ mol} \]
Ndalama yofunikira ikhoza kuwerengedwa pogwiritsa ntchito mtengo wa Faraday (F = 96485 C/mol e^-):
\[ Q = n \nthawi F \]
\[ Q = \left(\frac{2}{71} \text{ mol}\right) \times 96485 \text{ C/mol} \]
\[ Q = 2718 \malemba{ C} \]
Pomaliza:
- Zomwe zimachitika pa cathode:
\[ 2H_2O(l) + 2e^- \muvi wa kumanja H_2(g) + 2OH^-(aq) \]
- Kuyankha pa anode:
\[ 2Cl^-(aq) \movina Cl_2(g) + 2e^- \]
– Ndalama zonse zofunika kuti mupeze gramu imodzi ya Cl2 ndi 2718 C.
-
Chitsanzo 3: Ubale wa Nernst ndi Mikhalidwe Yosakhala Yachizolowezi
Funso:
Werengerani mphamvu ya selo ya voltaic yopangidwa kuchokera ku ma electrode a Ag/Ag+ okhala ndi kuchuluka kwa ma ion asiliva a 0.1 M ndi ma electrode a Zn/Zn2+ okhala ndi kuchuluka kwa 0.01 M. Mphamvu ya electrode yokhazikika ndi:
\[ E^o_{\text{Ag}^{+}/\text{Ag}} = +0.80 \, \text{V} \]
\[ E^o_{\text{Zn}^{2+}/\text{Zn}} = -0.76 \, \text{V} \]
Kukambirana:
Gawo loyamba ndi kulemba zomwe zimachitika:
– Kusungunuka kwa okosijeni pa anode (Zn):
\[ \text{Zn (s)} \rightarrow \text{Zn}^{2+} (aq) + 2e^- \]
- Kuchepetsa pa cathode (Ag):
\[ \text{Ag}^{+} (aq) + e^- \rightarrow \text{Ag (s)} \]
Kuyankha konse:
\[ \text{Zn (s)} + 2\text{Ag}^{+} (aq) \rightarrow \text{Zn}^{2+} (aq) + 2\text{Ag (s)} \]
Kutengera ndi equation ya Nernst:
\[ E_{\text{Cell}} = E^o_{\text{Cell}} – \left( \frac{0.0592}{n} \right) \log \left( \frac{[\text{product}]}{[\text{reactant}]} \right) \]
Kumene:
\[ n = 2 \]
Choyamba, werengerani E^o_{\text{Sel}}:
\[ E^o_{\text{Sel}} = E^o_{\text{Ag}^{+}/\text{Ag}} – E^o_{\text{Zn}^{2+}/\text{Zn}} \]
\[ E^o_{\text{Sel}} = 0.80 \, \text{V} – (-0.76 \, \text{V}) \]
\[ E^o_{\text{Cell}} = 1.56 \, \text{V} \]
Kenako, werengani mphamvu yeniyeni ya maselo pa kuchuluka komwe kwaperekedwa:
\[ E_{\text{Sel}} = 1.56 \, \text{V} – \left( \frac{0.0592}{2} \right) \log \left( \frac{[\text{Zn}^{2+}]}{[\text{Ag}^{+}]^2} \right) \]
\[ E_{\text{Sel}} = 1.56 \, \text{V} – \left( \frac{0.0592}{2} \right) \log \left( \frac{0.01}{(0.1)^2} \right) \]
\[ E_{\text{Sel}} = 1.56 \, \text{V} – 0.0296 \log \left( \frac{0.01}{0.01} \right) \]
\[ E_{\text{Cell}} = 1.56 \, \text{V} \]
Pomaliza:
- Machitidwe omwe amapezeka pa anode ndi cathode amakhalabe omwewo
- Mphamvu ya maselo yokhala ndi kuchuluka koperekedwa ndi 1.56 V
Nkhaniyi ikuwonetsa momwe mungathetsere mitundu ingapo ya mavuto mu electrochemistry, kuphatikizapo mavuto okhudzana ndi maselo a voltaic, maselo a electrolytic, ndi mawerengedwe pogwiritsa ntchito Nernst Equation. Kumvetsetsa bwino mfundo zomwe zili kumbuyo kwa redox reactions ndi luso logwiritsa ntchito deta ya electrochemical ndikofunikira kuti mupambane pothetsa mavuto amtunduwu.
