Laʻana o nā nīnau kūkākūkā hydrolysis paʻakai
ʻO ka hydrolysis paʻakai kahi hanana kemika e pili ana i ka hopena o ka paʻakai me ka wai, e hana ana i kahi waikawa a i ʻole ke kumu ma ke ʻano he huahana ʻaoʻao. He kumuhana koʻikoʻi kēia kaʻina hana i nā haʻawina kemika no ka mea hiki i ka hoʻomaopopo ʻana i ka hydrolysis paʻakai ke hāʻawi i ka ʻike kumu i nā waiwai o nā hopena a kōkua i ka hoʻoholo ʻana i ka pH o nā hopena. Ma kēia ʻatikala, e kūkākūkā mākou i kekahi mau pilikia hoʻohālike a me kā lākou mau hopena e pili ana i ka hydrolysis paʻakai.
Nā Manaʻo Kumu o ka Hydrolysis Paʻakai
Hana ʻia ka hydrolysis paʻakai ke palaho ka paʻakai i loko o ka wai a pane kāna mau ion me nā molekala wai e hana i kahi waikawa a i ʻole kumu. ʻAʻole e hydrolyze nā paʻakai a pau i ka wai; he kūlike kekahi, ʻo ia hoʻi, ʻaʻole lākou e hoʻololi i ka pH o ka hopena. Eia nō naʻe, hiki i kekahi mau paʻakai ke hana i nā hopena waikawa a kumu paha, ma muli o ke kumu o ka waikawa a me ke kumu i hoʻokumu i ka paʻakai.
No ka hoʻomaopopo ʻana i kēia ʻano hana, he mea nui e ʻike i kēia:
ʻO ka maʻamau, ʻaʻole i hana ʻia ka hydrolysis e nā paʻakai o nā waikawa ikaika a me nā kumu ikaika (e like me NaCl) a noho kūlike ka hopena.
– ʻO ka maʻamau, hoʻopuka nā paʻakai o nā waikawa nāwaliwali a me nā kumu ikaika (e like me CH3COONa) i nā hopena kumu.
– ʻO ka paʻakai o nā waikawa ikaika a me nā kumu nāwaliwali (e like me NH4Cl) e hana pinepine i nā hopena ʻakika.
– Hiki i nā paʻakai o nā waikawa nāwaliwali a me nā kumu nāwaliwali ke hana me ka wai a hoʻoholo i ka pH hope loa ma muli o ka ikaika pili o ka waikawa a me ke kumu.
Nā Nīnau Laʻana a me ke Kūkākūkā
Nīnau 1: Hydrolysis o ka Potassium Acetate (CH3COOK)
Nīnau:
He waikawa, kumu, a kūlike paha ka hopena potassium acetate (CH3COOK)? E kākau i ka hopena hydrolysis e hana ʻia a hoʻoholo i ka pH o ka hopena.
Kūkākūkā:
ʻO ka potassium acetate (CH3COOK) he paʻakai ia o kahi waikawa nāwaliwali (acetic acid, CH3COOH) a me kahi kumu ikaika (potassium hydroxide, KOH). Mai kēia, hiki iā mākou ke hoʻoholo he kumu paha ka hopena CH3COOK no ka mea hiki i ka acetate ion (CH3COO⁻) ke hydrolyze i loko o ka wai.
Penei ka hopena:
\[ CH_3COO^- + H_2O \rightleftharpoons CH_3COOH + OH^- \]
ʻAe nā iona acetate (CH3COO⁻) i nā protons (H⁺) mai ka wai (H2O) e hana i ka waikawa acetic (CH3COOH) a me nā iona hydroxide (OH⁻). ʻO ke alo o nā iona hydroxide (OH⁻) i loko o ka hopena e hoʻolilo ia i mea kumu.
No ka hoʻoholo ʻana i ka pH, pono mākou i ka nui o nā ion OH⁻. No ka laʻana, loaʻa iā mākou kahi hopena 0,1 M CH3COOK a ʻo ke kūpaʻa ionization o ka waikawa acetic (Ka) he 1,8 × 10⁻⁵.
ʻO nā ʻanuʻu i hana ʻia:
1. Ke hoʻohana nei i ke kumu paʻa (Kb) no ka ion CH3COO⁻:
\[ K_b = \frac{K_w}{K_a} = \frac{10^{-14}}{1,8 \times 10^{-5}} = 5,56 \times 10^{-10} \]
2. E hoʻokaʻawale i nā iona CH3COO⁻ i loko o ka hopena:
\[ K_b = \frac{[CH_3COOH][OH^-]}{[CH_3COO^-]} \]
E hoʻolilo i ke kekelē o ka dissociation i 'x':
\[ 5,56 \times 10^{-10} = \frac{x^2}{0,1-x} \]
Ke hoʻowahāwahā nei i ka \(x\) liʻiliʻi ma ka denominator, hiki iā mākou ke hoʻomaʻalahi:
\[ x^2 \approx 5,56 \times 10^{-11} \Rightarrow x = \sqrt{5,56 \times 10^{-11}} = 7,45 \times 10^{-6} \]
Ka nui o ka OH⁻:
\[ [OH^-] = 7,45 \times 10^{-6} \]
pOH o ka hopena:
pOH = -\log [OH^-] = -\log (7,45 \times 10^{-6}) \approx 5,13 \]
Ke hoʻohana nei i ka pilina ma waena o ka pH a me ka pOH:
\[ pH = 14 – pOH = 14 – 5,13 = 8,87 \]
No laila, he kumu ka hopena CH3COOK me ka pH ma kahi o 8,87.
Nīnau 2: Hydrolysis o Ammonium Chloride (NH4Cl)
Nīnau:
He waikawa, kumu, a kūlike paha ka hopena ammonium chloride (NH4Cl)? E kākau i ka hopena hydrolysis e hana ʻia a hoʻoholo i ka pH o ka hopena.
Kūkākūkā:
He paʻakai ka ammonium chloride (NH4Cl) o kahi waikawa ikaika (HCl) a me kahi kumu nāwaliwali (NH3). Mai kēia, hiki iā mākou ke hoʻoholo he waikawa ka hopena no ka mea hiki i ka ion ammonium (NH4⁺) ke hydrolyze i loko o ka wai.
Penei ka hopena:
\[ NH_4^+ + H_2O \rightleftharpoons NH_3 + H_3O^+ \]
Hāʻawi nā iona ammonium (NH4⁺) i nā protons (H⁺) i nā molekala wai (H2O) e hana i ka ammonia (NH3) a me nā iona hydronium (H3O⁺). ʻO ke alo o nā iona hydronium (H3O⁺) i loko o kēia hopena ke kumu o ka hopena i waikawa.
Eia kekahi laʻana, loaʻa iā mākou kahi hopena NH4Cl 0,1 M. ʻO ke kumu ionization constant (Kb) no NH3 he 1,8 × 10⁻⁵.
ʻO nā ʻanuʻu i hana ʻia:
1. Ke hoʻohana nei i ke kūpaʻa waikawa (Ka) no ka ion NH4⁺:
\[ K_a = \frac{K_w}{K_b} = \frac{10^{-14}}{1,8 \times 10^{-5}} = 5,56 \times 10^{-10} \]
2. E hoʻokaʻawale i nā iona NH4⁺ i loko o ka hopena:
\[ K_a = \frac{[NH_3][H_3O^+]}{[NH_4^+]} \]
E hoʻolilo i ke kekelē o ka dissociation i 'x':
\[ 5,56 \times 10^{-10} = \frac{x^2}{0,1-x} \]
Ke hoʻowahāwahā nei i ka \(x\) liʻiliʻi ma ka denominator, hiki iā mākou ke hoʻomaʻalahi:
\[ x^2 \approx 5,56 \times 10^{-11} \Rightarrow x = \sqrt{5,56 \times 10^{-11}} = 7,45 \times 10^{-6} \]
ka nui o ka H3O⁺:
\[ [H_3O^+] = 7,45 \times 10^{-6} \]
pH o ka hopena:
pH = -\log [H_3O^+] = -\log (7,45 \times 10^{-6}) \approx 5,13 \]
No laila, he ʻakika ka hopena NH4Cl me ka pH ma kahi o 5,13.
Ma nā hiʻohiʻona ʻelua ma luna, ʻike mākou pehea e hiki ai i ka ʻike ʻana i ke ʻano o ka hydrolysis ke kōkua i ka hoʻoholo ʻana i ke ʻano o kahi hopena. Ma ka hoʻopili ʻana i ke kūpaʻa kaulike ionization (Ka a i ʻole Kb) a me kekahi mau kuhi maʻalahi, hiki iā mākou ke hoʻoponopono maʻalahi i kēia mau pilikia.
ʻAʻole wale kēia kūkākūkā ʻana o nā pilikia hydrolysis paʻakai e hoʻomaʻamaʻa i nā mākau loiloi i nā helu makemakika akā hoʻoikaika pū kekahi i ka hoʻomaopopo ʻana i nā manaʻo kumu o ke kemika hopena. ʻO ka hoʻomaopopo ʻana pehea e hāʻawi ai nā ion o nā kumu like ʻole i nā protons a i ʻole nā mea ʻae i nā molekala wai, a pehea e pili ai kēia i ka pH o kahi hopena, he mea nui ia no ka hoʻopaʻa ʻana i nā kumuhana holomua he nui i ke kemika.
