Nā nīnau hoʻohālike a me ke kūkākūkā ʻana o nā waikawa a me nā kumu Arrhenius
He mau manaʻo koʻikoʻi nā waikawa a me nā kumu i ka kemika. ʻO kekahi o nā kumumanaʻo kaulana loa e wehewehe i ke ʻano o nā waikawa a me nā kumu ʻo ia ke kumumanaʻo ʻo Arrhenius. Wahi a Arrhenius, he hui ka waikawa, ke hoʻoheheʻe ʻia i ka wai, e hana i nā iona H⁺ (a i ʻole H₃O⁺), ʻoiai he hui ke kumu, ke hoʻoheheʻe ʻia i ka wai, e hana i nā iona OH⁻. Ma kēia ʻatikala, e kūkākūkā mākou i kekahi mau pilikia hoʻohālike e pili ana i nā waikawa a me nā kumu e like me ke kumumanaʻo ʻo Arrhenius, me kā lākou mau hopena.
Laʻana Nīnau 1
Nīnau:
Ua hoʻoheheʻe ʻia kahi hopena waikawa hydrochloric (HCl) 0,1 M i loko o ka wai. E helu i ka nui o nā ion H⁺ i loko o ka hopena.
Kūkākūkā:
Wahi a ke kumumanaʻo Arrhenius, he waikawa ʻo HCl no ka mea hoʻopuka ia i nā ion H⁺ ke hoʻoheheʻe ʻia i loko o ka wai. Penei ke ʻano o ka ionization no HCl i loko o ka wai:
\[ \kikokikona{HCl} \to \kikokikona{H}^+ + \kikokikona{Cl}^- \]
ʻO 0,1 M ka nui mua o HCl. ʻOiai he waikawa ikaika ʻo HCl e hoʻoheheʻe piha i loko o ka wai, e hana kēlā me kēia molekole HCl i hoʻokahi ion H⁺ a me hoʻokahi ion Cl⁻. No laila, ua like nō hoʻi ka nui o nā ion H⁺ i loko o ka wai me ka nui o HCl, ʻo ia hoʻi:
\[ [\kikokikona{H}^+] = 0,1 \kikokikona{ M} \]
No laila, ʻo ka nui o nā ion H⁺ i loko o kahi hopena HCl 0,1 M he 0,1 M.
Laʻana Nīnau 2
Nīnau:
E helu i ka pH o kahi hopena 0,01 M nitric acid (HNO₃).
Kūkākūkā:
He waikawa ikaika ka HNO₃ e hoʻokahe piha i ka wai, no laila penei ke ʻano o ka hoʻohālikelike ionization no HNO₃:
\[ \kikokikona{HNO}_3 \to \kikokikona{H}^+ + \kikokikona{NO}_3^- \]
ʻO ka nui o ka HNO₃ i hāʻawi ʻia he 0,01 M. ʻOiai he waikawa ikaika ʻo HNO₃, e hana kēlā me kēia mole o HNO₃ i hoʻokahi ion H⁺. No laila, ua like ka nui o nā ion H⁺ i loko o ka hopena me ka nui o ka HNO₃, ʻo ia hoʻi:
\[ [\kikokikona{H}^+] = 0,01 \kikokikona{ M} \]
Hiki ke helu ʻia ka pH me ka hoʻohana ʻana i ke ʻano hana:
\[ \kikokikona{pH} = -\log [\kikokikona{H}^+] \]
Ma ke kau ʻana i ka nui o nā ion H⁺ i loko o ke ʻano hana, loaʻa iā mākou:
\[ \text{pH} = -\log (0,01) = -\log (10^{-2}) = 2 \]
No laila, ʻo ka pH o kahi hopena 0,01 M HNO₃ he 2.
Laʻana Nīnau 3
Nīnau:
E hoʻoholo i ka nui o nā ion OH⁻ i loko o kahi hopena NaOH 0,05 M.
Kūkākūkā:
He kumu ikaika ʻo NaOH e hoʻokahe piha i ka wai, no laila penei ke ʻano o ka hoʻohālikelike ionization no NaOH:
\[ \text{NaOH} \to \text{Na}^+ + \text{OH}^- \]
ʻO ka nui o ka NaOH i hāʻawi ʻia he 0,05 M. ʻOiai he kumu ikaika ʻo NaOH, e hana kēlā me kēia molekole NaOH i hoʻokahi ion OH⁻. No laila, ua like ka nui o nā ion OH⁻ i loko o ka hopena me ka nui o ka NaOH, ʻo ia hoʻi:
\[ [\kikokikona{OH}^-] = 0,05 \kikokikona{ M} \]
No laila, ʻo ka nui o nā ion OH⁻ i loko o kahi hopena 0,05 M NaOH he 0,05 M.
Laʻana Nīnau 4
Nīnau:
E helu i ka pH o kahi hopena KOH 0,01 M.
Kūkākūkā:
He kumu ikaika ʻo KOH e hoʻokahe piha i ka wai. Penei ke ʻano hoʻohālikelike ionization no KOH i ka wai:
\[ \kikokikona{KOH} \to \kikokikona{K}^+ + \kikokikona{OH}^- \]
ʻO ka nui o KOH i hāʻawi ʻia he 0,01 M. ʻOiai he kumu ikaika ʻo KOH, e hana kēlā me kēia molekole KOH i hoʻokahi ion OH⁻. No laila, ua like ka nui o nā ion OH⁻ i loko o ka hopena me ka nui o KOH, ʻo ia hoʻi:
\[ [\kikokikona{OH}^-] = 0,01 \kikokikona{ M} \]
ʻO ka pH ke ana o ka nui o nā ion H⁺ i loko o kahi hopena. Hiki iā mākou ke hoʻohana i ka pilina ma waena o ka pH, nā ion H⁺, a me nā ion OH⁻ i hāʻawi ʻia e ka huahana ion wai (Kw):
\[ \text{Kw} = [\text{H}^+][\text{OH}^-] = 1 \times 10^{-14} \]
Ma ka ʻike ʻana i ka waiwai o [OH⁻], hiki iā mākou ke helu i ka [H⁺]:
\[ [\text{H}^+] = \frac{\text{Kw}}{[\text{OH}^-]} = \frac{1 \times 10^{-14}}{0,01} = 1 \times 10^{-12} \text{ M} \]
Hiki ke helu ʻia ka pH me ka hoʻohana ʻana i ke ʻano hana:
\[ \kikokikona{pH} = -\log [\kikokikona{H}^+] \]
Ma ke kau ʻana i ka nui o nā ion H⁺ i loko o ke ʻano hana, loaʻa iā mākou:
\[ \text{pH} = -\log (1 \times 10^{-12}) = 12 \]
No laila, ʻo ka pH o kahi hopena 0,01 M KOH he 12.
Laʻana Nīnau 5
Nīnau:
He pH ko kahi hopena = 3. E helu i ka nui o nā ion H⁺ i loko o ka hopena.
Kūkākūkā:
ʻO ka pH ke ana o ka nui o nā ion H⁺ i loko o kahi hopena a hiki ke hōʻike ʻia e ke ʻano:
\[ \kikokikona{pH} = -\log [\kikokikona{H}^+] \]
No ka helu ʻana i ka nui o nā ion H⁺, hoʻololi mākou i ke ʻano hana i:
\[ [\kikokikona{H}^+] = 10^{-\kikokikona{pH}} \]
Ma ke kau ʻana i nā waiwai pH i hāʻawi ʻia, loaʻa iā mākou:
\[ [\kikokikona{H}^+] = 10^{-3} = 0,001 \kikokikona{ M} \]
No laila, ʻo ka nui o nā ion H⁺ i loko o kahi hopena me ka pH = 3 he 0,001 M.
Laʻana Nīnau 6
Nīnau:
ʻO ka nui o ka hopena NH₄OH he 0,1 M. E helu i ka pH o ka hopena inā ʻo ka waiwai Kb no NH₄OH he 1,8 x 10⁻⁵.
Kūkākūkā:
He kumu nāwaliwali ka NH₄OH ʻaʻole ia e ionize piha i loko o ka wai. ʻO ke kaulike ionization no ka NH₄OH i loko o ka wai penei:
\[ \text{NH}_4\text{OH} \leftrightarrow \text{NH}_4^+ + \text{OH}^- \]
ʻO ke kūpaʻa kaulike no ka ionization o NH₄OH ua kapa ʻia ʻo Kb a ua hāʻawi ʻia e:
\[ K_b = \frac{[\text{NH}_4^+][\text{OH}^-]}{[\text{NH}_4\text{OH}} \]
ʻOiai he kumu nāwaliwali ʻo NH₄OH, hoʻohana mākou iā Kb e helu i ka nui o nā ion OH⁻. Ke manaʻo nei ʻo \(x\) ka nui o ka NH₄OH i hoʻohuihui ʻia, lilo ka hoʻohālikelike ionization:
\[ K_b = \frac{x^2}{0,1 – x} \approx \frac{x^2}{0,1} \]
ʻOiai he liʻiliʻi loa ka waiwai o Kb, ke manaʻo nei mākou \(0,1 – x \approx 0,1\):
\[ 1,8 \times 10^{-5} = \frac{x^2}{0,1} \]
\[ x^2 = 1,8 \times 10^{-6} \]
\[ x = \sqrt{1,8 \times 10^{-6}} \]
\[ x \approx 1,34 \times 10^{-3} \text{ M} \]
No laila, ʻo ka nui o nā ion OH⁻ he \(1,34 \times 10^{-3} \text{ M}\).
Mai kēia ʻano hoʻohuihui, hiki iā mākou ke helu i ka nui o nā ion H⁺ me ka hoʻohana ʻana iā Kw:
\[ [\text{H}^+] = \frac{1 \times 10^{-14}}{1,34 \times 10^{-3}} \]
\[ [\text{H}^+] = 7,46 \times 10^{-12} \text{ M} \]
pH:
\[ \text{pH} = -\log (7,46 \times 10^{-12}) \]
\[ \text{pH} \approx 11,13 \]
No laila, ʻo ka pH o kahi hopena NH₄OH 0,1 M ma kahi o 11,13.
Ka hopena
Hāʻawi ke kumumanaʻo Arrhenius i kahi kahua waiwai no ka hoʻomaopopo ʻana i ke ʻano o ka hana ʻana o nā waikawa a me nā kumu i loko o ka hopena. Ma kēia kūkākūkā ʻana, ua nānā mākou i kekahi mau pilikia hoʻohālike e hōʻike ana pehea e hiki ai ke hoʻohana ʻia kēia mau manaʻo e helu i nā nui o nā iona H⁺ a me OH⁻ a me ka pH o nā hopena like ʻole. He mea nui ka hoʻomaopopo ʻana i kēia kumumanaʻo no kekahi e ʻimi nei i kahi ʻoihana ma ke kemika, inā ma ke kula kiʻekiʻe a i ʻole ka pae hoʻonaʻauao kiʻekiʻe.
