Nā nīnau hoʻohālike e kūkākūkā ana i ka ikaika a me ka pH o nā waikawa a me nā kumu
He mau kumuhana koʻikoʻi ka ikaika o ke kumu waikawa a me ka pH i ke kemika, ʻoiai hoʻi ma ke kahua o nā waikawa a me nā kumu. Ma kēia ʻatikala, e kūkākūkā mākou pehea e hoʻoholo ai i ka ikaika o ka waikawa a me ke kumu a helu i ka pH o kahi hopena me ka hoʻohana ʻana i kekahi mau pilikia hoʻohālike.
Hoʻolauna i nā ʻakika a me nā kumu
Asama
He hui ka waikawa e hiki ke hoʻokuʻu i nā iona hydrogen (H⁺) ke hoʻoheheʻe ʻia i loko o ka wai. Ma muli o ko lākou hiki ke hoʻokuʻu i nā iona H⁺, ua hoʻokaʻawale ʻia nā waikawa i ʻelua ʻano:
1. ʻAkika ikaika: He ʻakika e hoʻokaʻawale 100% i loko o ka hopena, e hoʻokuʻu loa ana i nā iona H⁺. Nā Laʻana: ʻAkika hydrochloric (HCl), ʻakika sulfuric (H₂SO₄), ʻakika nitric (HNO₃).
2. ʻAkika nāwaliwali: He ʻakika e hoʻokaʻawale hapa wale ʻia i loko o ka hopena, hoʻokuʻu wale kekahi o nā molekala i nā iona H⁺. Nā Laʻana: ʻAkika ʻakika (CH₃COOH), ʻakika kalapona (H₂CO₃), ʻakika hydrocyanic (HCN).
kumu
He hui ka base e hiki ke hoʻokuʻu i nā ion hydroxide (OH⁻) ke hoʻoheheʻe ʻia i loko o ka wai. Ma muli o ko lākou hiki ke hoʻokuʻu i nā ion OH⁻, ua hoʻokaʻawale ʻia nā base i ʻelua ʻano:
1. Kumu ikaika: He kumu e hoʻokaʻawale 100% i loko o ka hopena, e hoʻokuʻu loa ana i nā iona OH⁻. Nā Laʻana: Sodium hydroxide (NaOH), potassium hydroxide (KOH).
2. Kumu nāwaliwali: He kumu e hoʻokaʻawale hapa wale ʻia i loko o ka hopena, hoʻokuʻu wale kekahi o nā molekala i nā iona OH⁻. Nā Laʻana: Ammonia (NH₃), magnesium hydroxide (Mg(OH)₂).
Manaʻo pH
ʻO ka pH ke ana o ka acidity a i ʻole ka alkalinity o kahi hopena. Ua wehewehe ʻia ʻo ia ka logarithm maikaʻi ʻole o ka nui o ka ion hydrogen (H⁺):
\[ \kikokikona{pH} = – \log [H⁺] \]
No nā hoʻonā kumu, hoʻohana ʻia hoʻi ka pOH, i wehewehe ʻia ʻo ia ka logarithm maikaʻi ʻole o ka nui o ka ion hydroxide (OH⁻):
\[ \kikokikona{pOH} = – \log [OH⁻] \]
ʻO ka pilina ma waena o ka pH a me ka pOH penei:
\[ \kikokikona{pH} + \kikokikona{pOH} = 14 \]
Ua kapa ʻia ka pH 7 he kū ʻole, ʻo ka pH ma lalo o 7 he waikawa, a ʻo ka pH ma luna o 7 he alkaline.
Nā Nīnau Laʻana a me ke Kūkākūkā
Laʻana Nīnau 1: Ke helu ʻana i ka pH o kahi ʻakika ikaika
Nīnau: E hoʻoholo i ka pH o kahi hopena HCl 0,01 M.
Kūkākūkā: He waikawa ikaika ʻo HCl e hoʻokaʻawale loa i nā iona H⁺ a me Cl⁻. No ka mea, he 1:1 ka molarity ma waena o HCl a me H⁺, ʻo ka nui o H⁺ he 0,01 M.
\[ \kikokikona{pH} = – \log [H⁺] \]
\[ \kikokikona{pH} = – \log (0,01) \]
\[ \kikokikona{pH} = 2 \]
No laila, ʻo ka pH o ka hopena 0,01 M HCl he 2.
Laʻana Nīnau 2: Ke helu ʻana i ka pH o kahi ʻakika nāwaliwali
Nīnau: E hoʻoholo i ka pH o kahi hopena 0,1 M CH₃COOH (ʻakika acetic) inā ʻo ka \( K_a \) o CH₃COOH he \( 1,8 \times 10^{-5} \).
Kūkākūkā: ʻAʻole hoʻokaʻawale loa nā waikawa nāwaliwali, no laila hoʻohana mākou i ke kūpaʻa hoʻokaʻawale waikawa ( \( K_a \) ) e hoʻoholo ai i ka nui o H⁺. No CH₃COOH, ʻo ke kaulike hoʻokaʻawale penei:
\[ \text{CH₃ COOH} \rightleftharpoons \text{H⁺} + \text{CH₃ COO⁻} \]
Mai ke kānāwai hoʻonā buffer, ke manaʻo nei mākou ʻo \( x \) ka nui o nā ion H⁺ i hoʻokumu ʻia:
\[ K_a = \frac{ [H⁺][CH₃ COO⁻] }{ [CH₃ COOH] } \]
\[ 1,8 manawa 10^{-5} = \frac{ (x)(x) }{ 0,1 – x } \]
ʻOiai he liʻiliʻi loa ʻo \( x \) i hoʻohālikelike ʻia me 0,1 M, hiki iā mākou ke hoʻowahāwahā i ka x ma ka denominator:
\[ 1,8 \times 10^{-5} \approx \frac{ x^2 }{ 0,1 } \]
\[ x^2 \approx 1,8 \times 10^{-6} \]
\[ x \approx \sqrt{ 1,8 \times 10^{-6} } \]
\[ x \approx 1,34 \times 10^{-3} \]
No laila, ʻo ka nui o H⁺ he \( 1,34 \times 10^{-3} \):
\[ \kikokikona{pH} = – \log [H⁺] \]
\[ \text{pH} = – \log (1,34 \times 10^{-3}) \]
\[ \text{pH} \approx 2,87 \]
No laila, ʻo ka pH o kahi hopena 0,1 M CH₃COOH ma kahi o 2,87.
Laʻana Nīnau 3: Ke helu ʻana i ka pH o kahi Kumu Ikaika
Nīnau: E hoʻoholo i ka pH o kahi hopena 0,01 M NaOH.
Kūkākūkā: He kumu ikaika ʻo NaOH e hoʻokaʻawale loa i nā iona Na⁺ a me OH⁻. No ka mea, he 1:1 molarity ma waena o NaOH a me OH⁻, ʻo ka nui o ka OH⁻ he 0,01 M.
\[ \kikokikona{pOH} = – \log [OH⁻] \]
\[ \kikokikona{pOH} = – \log (0,01) \]
\[ \kikokikona{pOH} = 2 \]
Ke hoʻohana nei i ka pilina \( \text{pH} + \text{pOH} = 14 \):
\[ \kikokikona{pH} = 14 – \kikokikona{pOH} \]
\[ \kikokikona{pH} = 14 – 2 \]
\[ \kikokikona{pH} = 12 \]
No laila, ʻo ka pH o ka hopena 0,01 M NaOH he 12.
Laʻana Nīnau 4: Ke helu ʻana i ka pH o kahi Base nāwaliwali
Nīnau: E hoʻoholo i ka pH o kahi hopena NH₃ 0,1 M inā ʻo ka \( K_b \) o NH₃ he \( 1,8 \times 10^{-5} \).
Kūkākūkā: ʻAʻole e hoʻokaʻawale loa nā kumu nāwaliwali, no laila hoʻohana mākou i ke kūpaʻa hoʻokaʻawale kumu ( \( K_b \) ) e hoʻoholo ai i ka nui o OH⁻. No NH₃, ʻo ke kaulike hoʻokaʻawale penei:
\[ \text{NH₃ + H₂O} \rightleftharpoons \text{NH₄⁺ + OH⁻} \]
Ma ka hoʻohana ʻana i ke ʻano hana like me nā waikawa nāwaliwali, ke manaʻo nei mākou ʻo \( y \) ka nui o nā ion OH⁻ i hoʻokumu ʻia:
\[ K_b = \frac{ [NH₄⁺][OH⁻] }{ [NH₃] } \]
\[ 1,8 \manawa 10^{-5} = \frac{ (y)(y) }{ 0,1 – y } \]
Ke manaʻo nei he liʻiliʻi ʻo \( y \), lilo ke kaulike:
\[ 1,8 \times 10^{-5} \approx \frac{ y^2 }{ 0,1 } \]
\[ y^2 \approx 1,8 \times 10^{-6} \]
\[ y \approx \sqrt{ 1,8 \times 10^{-6} } \]
\[ y \approx 1,34 \times 10^{-3} \]
ʻO ka nui o OH⁻ he \( 1,34 \times 10^{-3} \):
\[ \kikokikona{pOH} = – \log [OH⁻] \]
\[ \text{pOH} = – \log (1,34 \times 10^{-3}) \]
\[ \text{pOH} \approx 2,87 \]
Ke hoʻohana nei i ka pilina \( \text{pH} + \text{pOH} = 14 \):
\[ \kikokikona{pH} = 14 – 2,87 \]
\[ \text{pH} \approx 11,13 \]
No laila, ʻo ka pH o kahi hopena 0,1 M NH₃ ma kahi o 11,13.
Ka hopena
ʻO ka hoʻoholo ʻana i ka pH o kahi hopena a me ka hoʻomaopopo ʻana i nā ikaika o nā waikawa a me nā kumu he mau kumu nui ia i ka kemika. Hoʻokaʻawale loa nā waikawa ikaika a me nā kumu i loko o ka hopena, ʻoiai ʻo nā waikawa nāwaliwali a me nā kumu e hoʻokaʻawale hapa wale nō. ʻO ka hoʻohana ʻana iā \( K_a \) a me \( K_b \) e maʻalahi ai ka helu ʻana i ka pH o nā waikawa nāwaliwali a me nā kumu. He mea nui kēia mau mākau no nā noi ma nā ʻano like ʻole, me ka ʻoihana ʻoihana, lāʻau lapaʻau, a me ke kemika kaiapuni. Ma ka hoʻomaopopo ʻana i nā manaʻo a me ke aʻo ʻana i nā hiʻohiʻona, hiki iā mākou ke hoʻoponopono maʻalahi i nā pilikia e pili ana i ka pH a me ka ikaika o ka waikawa-kumu i ke ola o kēlā me kēia lā.
