Ngā Tauira o ngā Pātai me te Kōrero mō ngā Waikawa Ngoikore me ngā Kawenga Ngoikore
Pendahuluan
He ariā matua ngā waikawa me ngā kawakore i roto i te matū, he mea nui kia mārama. He mahi nui tā ngā waikawa ngoikore me ngā kawakore ngoikore i roto i ngā tauhohenga matū maha, i roto i ngā taiwhanga me te oranga o ia rā. Ka kapi tēnei tuhinga i ngā tauira rapanga me te matapakinga taipitopito mō ngā waikawa ngoikore me ngā kawakore ngoikore.
Te Mārama ki ngā Waikawa Ngoikore me ngā Kawenga Ngoikore
Waikawa ngoikore
Ko te waikawa ngoikore he waikawa kāore e tino wehea i roto i te wairewa. Ko te tikanga o tēnei, i roto i te wairewa waikawa ngoikore, he iti noa te wāhanga o ngā ngota waikawa ka wehea hei katote hauwai (\(\text{H}^+\)) me te anion honohono (\(\text{A}^-\)). Ko tētahi tauira noa o te waikawa ngoikore ko te waikawa acetic (\(\text{CH}_3\text{COOH}\)).
Pūtake ngoikore
Ko te turanga ngoikore he turanga kāore e tino wehea i roto i te wairewa. He iti noa te wehenga o ngā turanga ngoikore ki ngā katote hauwai (\(\text{OH}^-\)) me ngā kationa honohono. Ko tētahi tauira noa o te turanga ngoikore ko te haukini (\(\text{NH}_3\)).
Ngā Tātai Matū Taketake mō ngā Waikawa Ngoikore me ngā Pātū Ngoikore
Waikawa ngoikore
Ka taea te whakaatu i te tauhohenga wehenga o te waikawa ngoikore i roto i te wai mā te whārite e whai ake nei:
\[
\text{HA} \rightleftharpoons \text{H}^+ + \text{A}^-
\]
me \(\text{HA}\) hei waikawa ngoikore, me \(\text{A}^-\) hei anion honohono.
Ko te pūmau wehewehe waikawa (\(K_a\)) e whakamahia ana hei whakaahua i te kaha o te waikawa ngoikore:
\[
K_a = \frac{[\text{H}^+][\text{A}^-]}{[\text{HA}]}
\]
Pūtake ngoikore
Ka taea te whakaatu i te tauhohenga wehenga o tētahi turanga ngoikore i roto i te wai penei:
\[
\kāhua{B} + \kāhua{H}_2\kāhua{O} \tika-mau-mau-te-ringa \kāhua{BH}^+ + \kāhua{OH}^-
\]
me \(\text{B}\) hei turanga ngoikore, me \(\text{BH}^+\) hei kationa honohono.
Ko te pūmau wehewehe turanga (\(K_b\)) e whakamahia ana hei whakaahua i te kaha o tētahi turanga ngoikore:
\[
K_b = \frac{[\text{BH}^+][\text{OH}^-]}{[\text{B}]}
\]
Ngā Pātai Tauira me te Kōrero
Tauira Pātai 1: Waikawa Ngoikore
Pātai: Tātaihia te pH o tētahi otinga 0.1 M o te waikawa acetic (\(\text{CH}_3\text{COOH}\)) mēnā ko te \(K_a\) o te waikawa acetic ko \(1.8 \times 10^{-5}\).
Kōrero:
1. Tuhia te whārite wehewehe:
\[
\text{CH}_3\text{COOH} \rightleftharpoons \text{CH}_3\text{COO}^- + \text{H}^+
\]
2. Tāutuhia te kukū tīmatanga me te huringa o te kukū i roto i te ripanga ICE (Tīmatanga, Huringa, Taurite).
| | \(\kuputuhi{CH}_3\kuputuhi{COOH}\) | \(\kuputuhi{CH}_3\kuputuhi{COO}^-\) | \(\kuputuhi{H}^+\) |
|——-|——————————-|————————-|———————–|
| Tīmatanga | 0.1 M | 0 | 0 |
| Huri | -x | +x | +x |
| Taurite | 0.1 – x | x | x |
3. Honoa a \(K_a\) ki te kukū i te taurite:
\[
K_a = \frac{[H^+][CH_3COO^-]}{[CH_3COOH]} = \frac{x \cdot x}{0.1 – x}
\]
Nā te mea he iti a \(K_a\), he tika tonu te whakaaro \(x \ll 0.1\):
\[
K_a \approx \frac{x^2}{0.1}
\]
\[
1.8 \times 10^{-5} = \frac{x^2}{0.1}
\]
\[
x^2 = 1.8 \whakareatia ki te 10^{-6}
\]
\[
x = 1.34 \times 10^{-3}
\]
4. Tātaihia te pH:
\[
\text{pH} = -\log[H^+] = -\log(1.34 \times 10^{-3}) = 2.87
\]
Tauira Pātai 2: Ngā Pūtake Ngoikore
Pātai: Tātaihia te pOH o tētahi otinga haukini 0.05 M (\(\text{NH}_3\)) mēnā ko te \(K_b\) o te haukini he \(1.8 \times 10^{-5}\).
Kōrero:
1. Tuhia te whārite wehewehe:
\[
\text{NH}_3 + \text{H}_2\text{O} \rightleftharpoons \text{NH}_4^+ + \text{OH}^-
\]
2. Whakatauhia te kukū tīmatanga me te huringa o te kukū i roto i te ripanga ICE:
| | \(\kuputuhi{NH}_3\) | \(\kuputuhi{NH}_4^+\) | \(\kuputuhi{OH}^-\) |
|——-|———————–|——————-|——————|
| Tīmatanga | 0.05 M | 0 | 0 |
| Huri | -x | +x | +x |
| Taurite | 0.05 – x | x | x |
3. Honoa te \(K_b\) ki te kukū i te taurite:
\[
K_b = \frac{[\text{NH}_4^+][\text{OH}^-]}{[\text{NH}_3]} = \frac{x \cdot x}{0.05 – x}
\]
Ki te whakaaro \(x \ll 0.05\):
\[
K_b \approx \frac{x^2}{0.05}
\]
\[
1.8 \times 10^{-5} = \frac{x^2}{0.05}
\]
\[
x^2 = 9 \whakareatia ki te 10^{-7}
\]
\[
x = 3 \times 10^{-4}
\]
4. Tātaihia te pOH:
\[
\text{pOH} = -\log[OH^-] = -\log(3 \times 10^{-4}) = 3.52
\]
5. Tahurihia ki te pH mēnā e tika ana:
\[
pH = 14 – pOH = 14 – 3.52 = 10.48
\]
Whakamutunga
He tino āwhina te mārama ki ngā waikawa ngoikore me ngā turanga ngoikore mā roto i ngā tauira rapanga hei matapae i ō rātou whanonga matū i roto i te otinga. Mā te mārama ki ngā ariā o \(K_a\) me \(K_b\) me pēhea te huri i ngā kukū katote ki te pH, ki te pOH rānei, ka taea e tātou te tātari i ngā momo otinga i roto i ngā horopaki mātauranga me ngā horopaki ahumahi. Me haere tonu te whakaharatau me ngā momo rapanga hei whakahōhonu ake i tō māramatanga me ō pūkenga ki te tātari matū.
