Fa'ata'ita'iga o Fesili ma Talanoaga o 'Aseta Vaivai ma 'Aseta Vaivai
Pendahuluan
O 'asita ma fa'avae o ni manatu autū se lua i le kemisi e tāua tele ona malamalama i ai. E tāua tele matafaioi a 'asita vaivai ma fa'avae vaivai i le tele o tali fa'akemikolo, i totonu o fale su'esu'e ma le olaga i aso faisoo. O lenei tusiga o le a aofia ai fa'ata'ita'iga o fa'afitauli ma se talanoaga auiliili o 'asita vaivai ma fa'avae vaivai.
Malamalama i 'Asite Vaivai ma 'Asite Vaivai
'Aseta Vaivai
O le 'aisa vaivai o se 'aisa e lē fa'a'ese'ese atoatoa i totonu o se vai. O lona uiga, i totonu o se vai 'aisa vaivai, e na'o se vaega itiiti o mole mole 'aisa e fa'a'ese'ese i ni 'aisa haitorosene (\(\text{H}^+\)) ma le anion fa'atasi (\(\text{A}^-\)). O se fa'ata'ita'iga masani o se 'aisa vaivai o le 'aisa 'acetic (\(\text{CH}_3\text{COOH}\)).
Fa'avae Vaivai
O se fa'avae vaivai o se fa'avae e le fa'aeseese atoatoa i totonu o se vai. O fa'avae vaivai e na'o sina fa'aeseese teisi lava i ni ion hydroxide (\(\text{OH}^-\)) ma ni cation fa'atasi. O se fa'ata'ita'iga masani o se fa'avae vaivai o le ammonia (\(\text{NH}_3\)).
Fua Fa'avae Fa'akemikolo mo 'Aseta Vaivai ma Fa'avae Vaivai
'Aseta Vaivai
O le tali atu o le vavaeesega o se vailaʻau vaivai i le vai e mafai ona faʻaalia e ala i le fua faʻatatau lea:
\[
\text{HA} \rightleftharpoons \text{H}^+ + \text{A}^-
\]
fa'atasi ai ma le \(\text{HA}\) o se 'aseti vaivai ma le \(\text{A}^-\) o le anion fa'atasi.
O le acid dissociation constant (\(K_a\)) e fa'aaogaina e fa'amatala ai le malosi o se acid vaivai:
\[
K_a = \frac{[\text{H}^+][\text{A}^-]}{[\text{HA}]}
\]
Fa'avae Vaivai
O le tali atu o le vavaeʻeseina o se faʻavae vaivai i le vai e mafai ona faʻaalia e pei ona:
\[
\text{B} + \text{H}_2\text{O} \rightleftharpoons \text{BH}^+ + \text{OH}^-
\]
fa'atasi ai ma le \(\text{B}\) o se fa'avae vaivai ma le \(\text{BH}^+\) o le cation fa'atasi.
O le fa'avae o le dissociation constant (\(K_b\)) e fa'aaogaina e fa'amatala ai le malosi o se fa'avae vaivai:
\[
K_b = \frac{[\text{BH}^+][\text{OH}^-]}{[\text{B}]}
\]
Fesili Fa'ata'ita'i ma Talanoaga
Fa'ata'ita'iga Fesili 1: Vaivai o le 'Aseta
Fesili: Fuafua le pH o se vaifofo 0.1 M o le acetic acid (\(\text{CH}_3\text{COOH}\)) pe afai o le \(K_a\) o le acetic acid o le \(1.8 \times 10^{-5}\).
Talanoaga:
1. Tusi le fua fa'atatau o le vavae'esega:
\[
\text{CH}_3\text{COOH} \rightleftharpoons \text{CH}_3\text{COO}^- + \text{H}^+
\]
2. Fuafua le malosi muamua ma le suiga o le malosi i le laulau ICE (Initial, Change, Equilibrium).
| | \(\text{CH}_3\text{COOH}\) | \(\text{CH}_3\text{COO}^-\) | \(\text{H}^+\) |
|——-|——————————-|————————-|———————–|
| Muamua | 0.1 M | 0 | 0 |
| Suiga | -x | +x | +x |
| Paleni | 0.1 – x | x | x |
3. Fa'afeso'ota'i le \(K_a\) i le fa'aputuga i le paleni:
\[
K_a = \frac{[H^+][CH_3COO^-]}{[CH_3COOH]} = \frac{x \cdot x}{0.1 – x}
\]
Talu ai e la'ititi le \(K_a\), e masani ona aoga le manatu \(x \ll 0.1\):
\[
K_a \approx \frac{x^2}{0.1}
\]
\[
1.8 \times 10^{-5} = \frac{x^2}{0.1}
\]
\[
x^2 = 1.8 \times 10^{-6}
\]
\[
x = 1.34 \times 10^{-3}
\]
4. Fuafua le pH:
\[
\text{pH} = -\log[H^+] = -\log(1.34 \times 10^{-3}) = 2.87
\]
Fa'ata'ita'iga Fesili 2: Fa'avae Vaivai
Fesili: Fuafua le pOH o se vailaʻau ammonia e 0.05 M (\(\text{NH}_3\)) pe afai o le \(K_b\) o le ammonia e \(1.8 \times 10^{-5}\).
Talanoaga:
1. Tusi le fua fa'atatau o le vavae'esega:
\[
\text{NH}_3 + \text{H}_2\text{O} \rightleftharpoons \text{NH}_4^+ + \text{OH}^-
\]
2. Fuafua le malosi muamua ma le suiga i le malosi i le laulau ICE:
| | \(\text{NH}_3\) | \(\text{NH}_4^+\) | \(\text{OH}^-\) |
|——-|——————–|——————-|——————|
| Muamua | 0.05 M | 0 | 0 |
| Suiga | -x | +x | +x |
| Paleni | 0.05 – x | x | x |
3. Fa'afeso'ota'i le \(K_b\) i le fa'aputuga i le paleni:
\[
K_b = \frac{[\text{NH}_4^+][\text{OH}^-]}{[\text{NH}_3]} = \frac{x \cdot x}{0.05 – x}
\]
I le manatu \(x \ll 0.05\):
\[
K_b \approx \frac{x^2}{0.05}
\]
\[
1.8 \times 10^{-5} = \frac{x^2}{0.05}
\]
\[
x^2 = 9 \times 10^{-7}
\]
\[
x = 3 \times 10^{-4}
\]
4. Fuafua le pOH:
\[
\text{pOH} = -\log[OH^-] = -\log(3 \times 10^{-4}) = 3.52
\]
5. Liliu i le pH pe a manaʻomia:
\[
\text{pH} = 14 – \text{pOH} = 14 – 3.52 = 10.48
\]
I'uga
O le malamalama i vailaʻau vaivai ma vailaʻau faʻavae vaivai e ala i faʻataʻitaʻiga o faʻafitauli e matua fesoasoani tele i le vavaloina o a latou amioga faʻakemikolo i totonu o fofo. I le malamalama i manatu o le \(K_a\) ma le \(K_b\) ma le auala e liua ai le maualuga o ion i le pH poʻo le pOH, e mafai ona tatou iloiloina le tele o fofo i tulaga faʻaleaʻoaʻoga ma pisinisi. Faʻaauau pea ona faʻataʻitaʻi i faʻafitauli eseese e faʻalolotoina ai lou malamalama ma tomai i le auiliiliga o vailaʻau.
