Tusaalaha Su'aalaha Doodda Elektrokemistriga
Elektrokemistri waa laan kiimiko ah oo barta xiriirka ka dhexeeya falgallada kiimikada iyo isbeddellada tamarta korontada. Elektrokemistri, waxaa jira laba fikradood oo waaweyn: oksaydheynta (sii deynta elektrokemika) iyo dhimista (helitaanka elektrokemika). Hawshani waxaa lagu arki karaa laba nooc oo unugyada elektrokemikalka ah: unugyada voltaic (unugyada galvanic) iyo unugyada elektrokemikaalka ah. Hoos waxaa ku yaal qaar ka mid ah dhibaatooyinka tusaalaha ah iyo sharraxaaddooda si ay kaaga caawiyaan inaad fahamto elektrokemikariga.
Su'aal Tusaale ah 1: Unugga Voltaic
Su'aal:
Marka la siiyo unug voltaic ah oo leh elektroodhada zinc (Zn) iyo naxaasta (Cu) oo ku xiran buundada milixda. Zn waxaa lagu dhex shubaa xal 1 M ZnSO4 ah, Cu-na waxaa lagu dhex shubaa xal 1 M CuSO4 ah. Qor falgallada ka dhaca elektroodh kasta oo xisaabi farqiga suurtagalka ah (EMF) ee unugga voltaic-ga. Xogta suurtagalka elektroodka caadiga ah:
\[ E^o_{\qoraalka{Zn}^{2+}/\qoraalka{Zn}} = -0.76 \, \qoraalka{V} \]
\[ E^o_{\text{Cu}^{2+}/\text{Cu}} = +0.34 \, \text{V} \]
Dood:
Tallaabada ugu horreysa waa in la go'aamiyo falcelinta redox ee dhacda. Unug voltaic ah, falcelin redox oo iskeed ah ayaa dhacda halkaas oo
– Zinc (Zn) wuxuu maraa oksaydh:
\[ \text{Zn(s)} \rightarrow \text{Zn}^{2+} (aq) + 2e^- \]
– Naxaasta (Cu) ayaa la dhimayaa:
\[ \text{Cu}^{2+} (aq) + 2e^- \rightarrow \text{Cu (s)} \]
Wadarta guud ee falcelinta redox ee unugga voltaic waa:
\[ \text{Zn(s)} + \text{Cu}^{2+} (aq) \rightarrow \text{Zn}^{2+} (aq) + \text{Cu(s)} \]
Marka xigta, waxaan xisaabin doonnaa farqiga suurtagalka unugga:
\[ E_{\text{cell}} = E^o_{\text{cathode}} – E^o_{\text{anode}} \]
Halkee:
– Katoodhku waa elektroodka halkaas oo hoos u dhac (Cu) ka dhaco.
– Anode-ku waa elektroodka halkaas oo oksaydhku (Zn) ka dhaco.
Markaa,
\[ E_{\text{sel}} = 0.34 \, \text{V} – (-0.76 \, \text{V}) \]
\[ E_{\text{sel}} = 0.34 \, \text{V} + 0.76 \, \text{V} = 1.10 \, \text{V} \]
Gabagabo:
– Falcelinta ka dhacda anode-ka (Zn):
\[ \text{Zn(s)} \rightarrow \text{Zn}^{2+} (aq) + 2e^- \]
– Falcelinta ka dhacda katoodka (Cu):
\[ \text{Cu}^{2+} (aq) + 2e^- \rightarrow \text{Cu (s)} \]
– Farqiga suurtagalka unugyada (EMF): 1.10 V
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Su'aal Tusaale 2: Unugga Elektrolitik-ga
Su'aal:
Marka la isticmaalayo elektrolisis-ka xalka NaCl, sheeg falcelinta ka dhacda katooliga iyo anode-ka haddii la isticmaalo elektrodi aan firfircoonayn, sida platinum (Pt). Xisaabi wadarta guud ee loo baahan yahay si loo soo saaro 1 garaam oo Cl2 ah. (Ar Cl = 35.5)
Dood:
Tallaabada ugu horreysa waa in la qoro falcelinta ka dhacda elektroodh kasta oo ku jira xalka milixda NaCl.
– Katooliga (hoos u dhigista):
Hawshan, ayoonada H+ ee biyaha ayaa la dhimi doonaa:
\[ 2H_2O (l) + 2e ^ - \ toosan H_2 (g) + 2OH^-(aq) \]
– Aanoodka (oksaydhaynta):
Cl-ion-ku wuxuu mari doonaa oksaydh si uu u noqdo gaaska Cl2:
\[ 2Cl^-(aq) \arrow Cl_2(g) + 2e^- \]
Falcelinta Guud:
Markaa falcelinta guud ee ka dhacda electrolysis-ka xalka NaCl waa:
\[ 2NaCl(aq) + 2H_2O(l) \rightarrow 2NaOH(aq) + H_2(g) + Cl_2(g) \]
Si loo xisaabiyo kharashka loo baahan yahay si loo soo saaro 1 garaam oo Cl2 ah, waxaan u baahanahay inaan go'aamino tirada moles-ka Cl2:
\[ \text{Culs of Cl}_2 = 1 \text{gram} \]
\[ \text{Ar Cl}_2 = 2 \jeer 35.5 = 71 \text{gram/mol} \]
\[ \text{Tirada burooyinka Cl}_2 = \frac{1}{71} \text{ mol} \]
Iyada oo ku saleysan isla'egta falgalka ee anode-ka, 1 mol oo Cl2 ah ayaa laga soo saaraa 2 mol oo elektaroono ah:
\[ 2Cl^- \arrow-ka midig Cl_2 + 2e^- \]
Si kale haddii loo dhigo, 1 mole oo Cl2 ah wuxuu u baahan yahay 2 mole oo elektaroono ah.
Tirada burooyinka elektaroonnada:
\[ \text{Tirada moolalka elektroonada} = 2 \jeer \frac{1}{71} = \frac{2}{71} \text{ mol} \]
Kharashka loo baahan yahay waxaa lagu xisaabin karaa iyadoo la isticmaalayo qiimaha Faraday (F = 96485 C/mol e^-):
\[ Q = n \times F \]
\[ Q = \left(\frac{2}{71} \text{ mol}\right) \times 96485 \text{ C/mol} \]
\[ Q = 2718 \qoraal{ C} \]
Gabagabo:
- Falcelinta kaatoodhka:
\[ 2H_2O (l) + 2e ^ - \ toosan H_2 (g) + 2OH^-(aq) \]
- Falcelinta anode-ka:
\[ 2Cl^-(aq) \arrow Cl_2(g) + 2e^- \]
– Wadarta guud ee loo baahan yahay si loo soo saaro 1 garaam oo Cl2 ah waa 2718 C.
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Tusaale 3: Xiriirka Nernst iyo Xaaladaha Aan Caadiga Ahayn
Su'aal:
Xisaabi kartida unug voltaic ah oo laga sameeyay elektroodhada Ag/Ag+ oo leh fiirsashada ion-ka qalinka ah ee 0.1 M iyo elektroodhada Zn/Zn2+ oo leh fiirsashada 0.01 M. Awoodda elektroodka caadiga ah waa:
\[ E^o_{\text{Ag}^{+}/\text{Ag}} = +0.80 \, \text{V} \]
\[ E^o_{\qoraalka{Zn}^{2+}/\qoraalka{Zn}} = -0.76 \, \qoraalka{V} \]
Dood:
Tallaabada ugu horreysa waa in la qoro falcelinta dhacda:
– Oksaydhaynta anode-ka (Zn):
\[ \text{Zn(s)} \rightarrow \text{Zn}^{2+} (aq) + 2e^- \]
- Hoos u dhac ku yimaada katoodka (Ag):
\[ \text{Ag}^{+} (aq) + e^- \rightarrow \text{Ag(s)} \]
Falcelinta guud:
\[ \text{Zn(s)} + 2\text{Ag}^{+} (aq) \rightarrow \text{Zn}^{2+} (aq) + 2\text{Ag(s)} \]
Iyada oo ku saleysan isla'egta Nernst:
\[ E_{\text{Cell}} = E^o_{\text{Cell}} – \left( \frac{0.0592}{n} \right) \log \left( \frac{[\text{product}]}{[\text{reactant}]} \right) \]
Halkee:
\[ n = 2 \]
Marka hore, xisaabi E^o_{\text{Sel}}:
\[ E^o_{\text{Sel}} = E^o_{\text{Ag}^{+}/\text{Ag}} – E^o_{\text{Zn}^{2+}/\text{Zn}} \]
\[ E^o_{\text{Sel}} = 0.80 \, \text{V} – (-0.76 \, \text{V}) \]
\[ E^o_{\text{Cell}} = 1.56 \, \text{V} \]
Marka xigta, xisaabi kartida unugga dhabta ah ee xoogga la bixiyay:
\[ E_{\text{Sel}} = 1.56 \, \text{V} – \left( \frac{0.0592}{2} \right) \log \left( \frac{[\text{Zn}^{2+}]}{[\text{Ag}^{+}]^2} \right) \]
\[ E_{\text{Sel}} = 1.56 \, \text{V} – \left( \frac{0.0592}{2} \right) \log \left( \frac{0.01}{(0.1)^2} \right) \]
\[ E_{\text{Cell}} = 1.56 \, \text{V} – 0.0296 \log \left( \frac{0.01}{0.01} \right) \]
\[ E_{\text{Cell}} = 1.56 \, \text{V} \]
Gabagabo:
– Falcelinta ka dhacda anode-ka iyo kathode-ku waxay ahaanayaan isku mid.
– Awoodda unugga ee leh xoog la siiyay waa 1.56 V
Maqaalkani wuxuu muujinayaa sida loo xalliyo dhowr nooc oo dhibaatooyin ah oo ku jira kiimikada korontada, oo ay ku jiraan dhibaatooyinka ku lug leh unugyada voltaic, unugyada korontada ku shaqeeya, iyo xisaabinta iyadoo la adeegsanayo Isle'egta Nernst. Faham buuxa oo ku saabsan mabaadi'da ka dambeysa falcelinta redox iyo awoodda loo leeyahay in la isticmaalo xogta korontada ku shaqeeya ayaa lagama maarmaan u ah guusha xallinta noocyadan dhibaatooyinka.
