Zitsanzo za Mafunso Okambirana za Mayankho a Buffer
Njira yothetsera vutoli, yomwe nthawi zambiri imatchedwa buffer, ndi njira yothetsera vutoli yomwe imasunga pH yake ngakhale asidi kapena maziko ake atakhala ochepa. Luso limeneli limapangitsa kuti njira zothetsera vutoli zikhale zofunika kwambiri pa ntchito zosiyanasiyana za mankhwala, zamoyo, komanso mafakitale. M'nkhaniyi, tifufuza zitsanzo zina ndikukambirana njira zothetsera vutoli.
Kumvetsetsa Mayankho a Buffer
Mayankho a Buffer nthawi zambiri amakhala ndi chisakanizo cha asidi wofooka ndi maziko ake olumikizana kapena maziko ofooka ndi asidi wake wolumikizana. Pamene asidi kapena maziko awonjezeredwa ku mayankho awa, zomwe zimachitika zimathandiza kuti pH ya yankho ikhalebe mkati mwa mtundu winawake. Pankhaniyi, pH ndi muyeso wa acidity kapena alkalinity ya yankho.
Ntchito ndi Kufunika kwa Ma Buffer Solutions
Mayankho a Buffer ali ndi gawo lofunika kwambiri m'magawo osiyanasiyana:
1. Biochemistry: Machitidwe ambiri a enzymatic ndi physiological amachitika pa pH inayake, kotero njira zosungiramo zinthu zimathandiza kusunga zinthu bwino.
2. Makampani: M'makampani ogulitsa zakudya ndi mankhwala, kuwongolera pH koyenera ndikofunikira kwambiri pa ubwino ndi chitetezo cha mankhwala.
3. Kuyesera kwa Mankhwala: Mu labotale, njira zosungira madzi zimagwiritsidwa ntchito polamulira pH panthawi ya zochita za mankhwala.
Momwe Ma Buffer Solutions Amagwirira Ntchito
Mayankho a Buffer amagwira ntchito motsatira mfundo ya equilibrium. Pa yankho lokhala ndi asidi wofooka \(HA \) ndi mchere wake wozungulira \(A^- \), kuwonjezera asidi pang'ono kapena maziko kumayambitsa kusintha kwa kayendedwe popanda kusintha kwakukulu mu kuchuluka kwa ma ayoni \(H^+ \) .
Mafunso ndi Kukambirana Zitsanzo
Kuti timvetse bwino, tiyeni tikambirane mafunso ndi zokambirana zokhudzana ndi mayankho a buffer.
Funso 1: Kuwerengera pH ya Acid Buffer Solution
Funso:
Njira yothetsera vutoli imapangidwa posakaniza 0,1 mol ya acetic acid (CH₃COOH) ndi 0,1 mol ya sodium acetate (CH₃COONa) mu lita imodzi ya yankho. Kugawanika kwa acetic acid (\( K_a \)) ndi \( 1,8 \times 10^{-5} \). Werengani pH ya yankho.
Kukambirana:
Njira yothetsera vutoli imakhala ndi asidi wofooka (CH₃COOH) ndi conjugate base yake (CH₃COO⁻). Tingagwiritse ntchito equation ya Henderson-Hasselbalch kuti tiwerengere pH ya yankho la buffer:
\[ \text{pH} = \text{p}K_a + \log \left( \frac{[A^-]}{[HA]} \right) \]
Kumene:
\[ \text{p}K_a = -\log (K_a) \]
\[ \text{p}K_a = -\log (1,8 \times 10^{-5}) \]
\[ \text{p}K_a \pafupifupi 4,74 \]
Popeza kuchuluka kwa \( [A^-] \) ndi \( [HA] \) kuli kofanana (0,1 M):
\[ \text{pH} = 4,74 + \log \left( \frac{[0,1]}{[0,1]} \right) \]
\[ \malemba{pH} = 4,74 + \log(1) \]
\[ \malemba{pH} = 4,74 \]
Chifukwa chake, pH ya yankho la buffer ndi 4,74.
Funso 2: Kuwonjezera Acid ku Buffer Solution
Funso:
Kodi kusintha kwa pH ndi kotani ngati 0,01 mol ya HCl yowonjezeredwa ku lita imodzi ya yankho la buffer kuchokera ku Funso 1?
Kukambirana:
Kuonjezera HCl kudzawonjezera kuchuluka kwa \( H^+ \) mu yankho. Zomwe zimachitika ndi izi:
\[ \text{H}^+ + \text{CH}_3\text{COO}^- \rightarrow \text{CH}_3\text{COOH} \]
Tifunika kuwerengera kuchuluka kwa ma moles a \( H^+ \) ndi momwe zimakhudzira kuchuluka kwa \( \text{CH}_3\text{COOH} \) ndi \( \text{CH}_3\text{COO}^- \).
Poyamba:
\[ [\text{CH}_3\text{COO}^-] = 0,1 \, \text{mol} \]
\[ [\text{CH}_3\text{COOH}] = 0,1 \, \text{mol} \]
Mukawonjezera 0,01 mol ya HCl:
\[ [\text{CH}_3\text{COO}^-] = 0,1 – 0,01 = 0,09 \, \text{mol} \]
\[ [\text{CH}_3\text{COOH}] = 0,1 + 0,01 = 0,11 \, \text{mol} \]
Gwiritsani ntchito equation ya Henderson-Hasselbalch kuti muwerengere pH yatsopano:
\[ \text{pH} = \text{p}K_a + \log \left( \frac{[A^-]}{[HA]} \right) \]
\[ \text{pH} = 4,74 + \log \left( \frac{0,09}{0,11} \right) \]
\[ \malemba{pH} = 4,74 + \log(0,818) \]
\[ \malemba{pH} = 4,74 + (-0,088) \]
\[ \malemba{pH} = 4,65 \]
Chifukwa chake, pH ya yankho la buffer pambuyo powonjezera HCl imasintha kuchoka pa 4,74 kufika pa 4,65.
Funso 3: Kuwonjezera Base ku Buffer Solution
Funso:
Kodi kusintha kwa pH ndi kotani ngati 0,01 mol ya NaOH yonjezedwa ku lita imodzi ya yankho la buffer kuchokera ku Funso 1?
Kukambirana:
Kuonjezera NaOH kudzachepetsa kuchuluka kwa H⁺ mu yankho ndi OH⁻ kuchokera ku NaOH. Zomwe zimachitika:
\[ \text{OH}^- + \text{CH}_3\text{COOH} \rightarrow \text{CH}_3\text{COO}^- + \text{H}_2\text{O} \]
Poyamba:
\[ [\text{CH}_3\text{COOH}] = 0,1 \, \text{mol} \]
\[ [\text{CH}_3\text{COO}^-] = 0,1 \, \text{mol} \]
Pambuyo powonjezera 0,01 mol ya NaOH:
\[ [\text{CH}_3\text{COOH}] = 0,1 – 0,01 = 0,09 \, \text{mol} \]
\[ [\text{CH}_3\text{COO}^-] = 0,1 + 0,01 = 0,11 \, \text{mol} \]
Gwiritsani ntchito equation ya Henderson-Hasselbalch kuti muwerengere pH yatsopano:
\[ \text{pH} = \text{p}K_a + \log \left( \frac{[A^-]}{[HA]} \right) \]
\[ \text{pH} = 4,74 + \log \left( \frac{0,11}{0,09} \right) \]
\[ \malemba{pH} = 4,74 + \log(1,222) \]
\[ \malemba{pH} = 4,74 + 0,087 \]
\[ \malemba{pH} = 4,83 \]
Chifukwa chake, pH ya yankho la buffer pambuyo powonjezera NaOH imasintha kuchokera pa 4,74 kufika pa 4,83.
Funso 4: Kudziwa Kuphatikizika kwa Buffer ndi pH inayake
Funso:
Kuti mupange lita imodzi ya yankho la buffer ndi pH 5,0 pogwiritsa ntchito acetic acid (CH₃COOH) ndi sodium acetate (CH₃COONa), kodi mukufunika ma moles angati a gawo lililonse? \( K_a \) ya acetic acid ndi \( 1,8 \times 10^{-5} \).
Kukambirana:
Gwiritsani ntchito equation ya Henderson-Hasselbalch:
\[ \text{pH} = \text{p}K_a + \log \left( \frac{[A^-]}{[HA]} \right) \]
Choyamba, werengerani pKₐ:
\[ \text{p}K_a = -\log (1,8 \times 10^{-5}) \]
\[ \text{p}K_a \pafupifupi 4,74 \]
Kenako, lowetsani pH yomwe mukufuna:
\[ 5,0 = 4,74 + \log \left( \frac{[A^-]}{[HA]} \right) \]
\[ 0,26 = \log \left( \frac{[A^-]}{[HA]} \right) \]
Kugwiritsa ntchito makhalidwe a ma logarithm:
\[ \frac{[A^-]}{[HA]} = 10^{0,26} \]
\[ \frac{[A^-]}{[HA]} \pafupifupi 1,82 \]
Izi zikutanthauza kuti pa mole imodzi iliyonse ya CH₃COOH, ma mole 1,82 a CH₃COONa amafunika. Pa chiŵerengero ichi mu lita imodzi:
Mwachitsanzo, tiyeni tinene kuti CH₃COOH = x mol, kotero CH₃COONa = 1,82x mol. Voliyumu yonse ndi (x + 1.82x) = 2,82x mol, popeza tikupanga lita imodzi ya buffer, ndiye kuti:
\[x + 1.82x = 1 \]
\[ 2.82x = 1 \]
\[ x = \frac{1}{2.82} \pafupifupi 0.355 \]
Kotero, kapangidwe kofunikira:
– CH₃COOH: 0,355 mol
- CH₃COONA: 1,82 0,355 ≈ 0,646 mol
Motero tikufunika 0,355 mol ya acetic acid ndi 0,646 mol ya sodium acetate kuti tipange lita imodzi ya yankho la buffer ndi pH 5,0.
Nkhaniyi ikupereka zitsanzo zosiyanasiyana za mavuto okhudzana ndi mayankho a buffer ndi zokambirana zawo kuti timvetsetse bwino lingaliro ili. Tikukhulupirira kuti izi zithandiza kumvetsetsa momwe mayankho a buffer amagwirira ntchito ndi momwe amagwiritsidwira ntchito m'malo osiyanasiyana.
