Me pēhea te whakatau i te pH o tētahi otinga: He aratohu whai hua me ngā mōhiohio hōhonu
He ariā matua te pH i roto i te matū, e whai pūtake ana i ngā tono maha i roto i te pūtaiao taiao, te koiora, te ahuwhenua, tae atu ki te pūtaiao tunu kai. I roto i tēnei tuhinga, ka matapakihia e mātou me pēhea te whakatau i te pH o tētahi otinga, mai i ngā ariā taketake ki ngā tikanga mahi tae noa ki ngā tono.
Te Māramatanga me ngā Ariā Taketake o te pH
Ko te pH he ine i te kukū o ngā iona hauwai (H+) i roto i tētahi otinga. Ko te tauine pH kei waenganui i te 0 ki te 14, me:
– Ko te pH 7 e tohu ana i tētahi otinga kūpapa (hei tauira, wai parakore),
– ko te pH iti iho i te 7 e tohu ana i te otinga waikawa (hei tauira, te waikawa hauwai),
– Ko te pH neke atu i te 7 e tohu ana i tētahi otinga papatipu (hei tauira, te houra tunutunu).
Ko te whanaungatanga pāngarau mō te pH ko:
\[ \kuputuhi{pH} = -\log[H^+] \]
ko \([H^+]\) te kukū o ngā iona hauwai i roto i ngā mole ia rita.
Ngā āhuatanga e pā ana ki te pH
Ngā mea katoa ka taea e ngā āhuatanga te awe pH o tētahi otinga:
– Momo me te Kukū o te Waikawa/Pūtake: Ka pā tika te kukū o ngā katote H\(^+\) OH\(^-\) rānei e ahu mai ana i ngā waikawa kaha, i ngā pūtake kaha rānei ki te pH.
– Pūwero: Ko te pūwero he otinga ka taea te pupuri i te pH i roto i tētahi awhe, ahakoa he iti noa te waikawa, te kawa rānei ka tāpirihia. Ko ngā pūwero he mea hanga mai i waikawa ngoikore me tōna turanga honohono.
– Te Pāmahana: Ka heke te pH o te wai parakore i te pikinga o te pāmahana nā te nui haere o te wehenga o te wai ki te H\(^+\) me te OH\(^-\).
Tikanga Whakatau pH
He maha ngā tikanga hei whakatau i te pH o tētahi otinga, i runga i ngā taputapu me ngā āhuatanga e wātea ana:
1. Pepa Ritmus me te Tohu Ao Whānui
He taputapu māmā, he iti hoki te utu mō te ine i te pH te pepa litmus me te tohu whānui. Ka rerekē te tae o te pepa litmus, o te wai tohu rānei, i runga i te pH o te wai:
– Pepa Ritmus: Kei roto ko te ritmus whero (hei whakamātautau i ngā turanga, ka huri ki te kikorangi i roto i ngā turanga) me te ritmus kikorangi (hei whakamātautau i ngā waikawa, ka huri ki te whero i roto i ngā waikawa).
– Tohu Ao Whānui: He matatau ake, e whakarato ana i te whānuitanga o ngā tae motuhake ka taea te whakarite ki tētahi ripanga tae paerewa hei whakatau i te pH.
2. Mita pH
He taputapu hiko tino tika te mita pH mō te ine i te pH. Ko ngā mea kei roto i tēnei taputapu ko:
– Irahiko Karāhe: Tairongo ki ngā iona H\(^+\).
– Irahiko Tohutoro: He pūmanawa pumau hei whakataurite.
– Mita Hiko: E whakaatu ana i ngā hua ine pH.
Ngā taahiraa mō te whakamahi i te mita pH:
– Whakatikatika: I mua i te whakamahinga, me whakatikatika te mita pH mā te whakamahi i tētahi otinga ārai me te pH e mōhiotia ana.
– Ine: Tōia te hikohiko ki roto i te wai hei ine, kātahi ka pānuihia ngā hua i runga i te mata.
3. Tikanga Tātaitanga
Ka taea hoki te whakatau i te pH mā te titration, inā koa mō ngā otinga buffer, ngā pūnaha rānei me ngā tauhohenga waikawa-pūtake:
– Te Whakatōpūtanga Waikawa-Pūtake: Mā te whakamahi i tētahi otinga paerewa (ko te tikanga he NaOH mō te pūtake, he HCl rānei mō te waikawa) hei whakatau i te kukū o tētahi otinga kāore i te mōhiotia i runga i te pūwāhi ōrite (ina rite te maha o ngā ira o te waikawa ki te maha o ngā ira o te pūtake).
– Te Whakamahinga o ngā Tohu: Ka tohua te pūwāhi ōrite e te panonitanga o te tae o te tohu ira tātai.
4. Te tatau i te pH mai i te Kukū
Mō ngā otinga māmā o ngā waikawa monoprotic kaha, ngā turanga rānei, ka taea te tatau tika i te pH mai i te kukū:
– Waikawa Kaha: \[ \text{pH} = -\log[H^+] \]
– Pūtake Kaha: \[ \text{pOH} = -\log[OH^-] \] kātahi ka \[ \text{pH} = 14 – \text{pOH} \]
Mō ngā waikawa ngoikore, mō ngā turanga ngoikore rānei, he uaua ake ngā tātaitanga, ā, me whakamahi te pūmau wetewete (Ka, Kb rānei).
Tono Whakatau pH
1. Ahumahi Kai me te Inu
– He mea tino nui te whakatau i te pH i roto i te hanga o ngā momo hua kai me inu hei whakarite i te reka, te kakano me te haumaru o te hua.
2. Te Taiwhanga Matū me te Koiora
– He mea nui te pH tika mō ētahi tauhohenga matū me te pupuri i ngā āhuatanga tino pai i roto i ngā mahi taiwhanga, pērā i te ahurea pūtau me ngā whakamātautau whākōkī.
3. Ahuwhenua
– Me aroturuki te pH o te oneone kia pai ai te tipu o ngā tipu. Ka ārai pea te pH kāore i te tika te mimiti o ngā matūkai e ngā tipu.
4. Rangahau Taiao
– He mea nui te aroturuki i te pH o te wai i roto i ngā taiao tūturu hei pupuri i ngā pūnaha rauropi me te kimi i te parahanga.
Whakamutunga
He pūkenga nui te whakatau i te pH o tētahi otinga, ā, he maha ngā whakamahinga whai hua. Kia mārama ki ngā ariā taketake o te pH, whakamahia te tikanga tika mō ō hiahia, ā, whakatikatikahia ō taputapu ine i ia wā kia tika ai ngā hua. Mā te mōhio ki tēnei tikanga ka taea te whakarite i ngā tukanga whai hua me te haumaru. Ahakoa he ākonga koe, he kairangahau, he kaimahi rānei, he mea tino nui te mōhio ki te whakatau i te pH i roto i ngā āhuatanga maha.
