Chitsanzo cha Mafunso Okambirana za Kusakaniza Madzi ndi Mchere
Kuthira mchere ndi chinthu chomwe chimachitika chifukwa cha momwe mchere umachitira ndi madzi, zomwe zimapangitsa kuti asidi kapena maziko a chinthucho apangidwe. Njira imeneyi nthawi zambiri imakhala yofunika kwambiri m'maphunziro a chemistry chifukwa kumvetsetsa kuthira mchere kungapereke chidziwitso chofunikira pa makhalidwe a mayankho ndikuthandizira kudziwa pH ya mayankho. M'nkhaniyi, tikambirana zitsanzo zingapo za mavuto ndi mayankho awo okhudzana ndi kuthira mchere.
Mfundo Zoyambira za Hydrolysis ya Mchere
Kuchuluka kwa mchere kumachitika pamene mchere umawola m'madzi ndipo ma ayoni ake amakumana ndi mamolekyu amadzi kuti apange asidi kapena maziko. Si mchere wonse womwe umasungunuka m'madzi; wina ndi wosalowerera, zomwe zikutanthauza kuti susintha pH ya yankho. Komabe, mchere wina ukhoza kupanga mayankho a acid kapena oyambira, kutengera komwe asidi ndi maziko adachokera.
Kuti mumvetse njira imeneyi, ndikofunikira kudziwa kuti:
– Mchere wa asidi amphamvu ndi maziko amphamvu (monga NaCl) nthawi zambiri sudutsa mu hydrolysis ndipo yankho silikhala lopanda mbali.
– Mchere wa ma asidi ofooka ndi maziko olimba (monga CH3COONa) nthawi zambiri umapanga mayankho oyambira.
– Mchere wa asidi amphamvu ndi maziko ofooka (monga NH4Cl) nthawi zambiri umapanga njira zochepetsera asidi.
– Mchere wa asidi wofooka ndi maziko ofooka amatha kuchitapo kanthu ndi madzi ndikupeza pH yomaliza kutengera mphamvu ya asidi ndi maziko.
Mafunso ndi Kukambirana Zitsanzo
Funso 1: Hydrolysis ya Potassium Acetate (CH3COOK)
Funso:
Kodi yankho la potaziyamu acetate (CH3COOK) ndi losalimba, losavuta, kapena lopanda ndale? Lembani momwe hydrolysis imachitikira ndikupeza pH ya yankho.
Kukambirana:
Potaziyamu acetate (CH3COOK) ndi mchere wa asidi wofooka (acetic acid, CH3COOH) ndi maziko olimba (potassium hydroxide, KOH). Kuchokera apa, tinganene kuti yankho la CH3COOK mwina ndi losavuta chifukwa ayoni ya acetate (CH3COO⁻) imatha kusungunuka m'madzi.
Yankho lake ndi motere:
\[ CH_3COO^- + H_2O \rightleftharpoons CH_3COOH + OH^- \]
Ma ayoni a acetate (CH3COO⁻) amalandira ma protoni (H⁺) ochokera m'madzi (H2O) kuti apange acetic acid (CH3COOH) ndi ma ayoni a hydroxide (OH⁻). Kupezeka kwa ma ayoni a hydroxide (OH⁻) mu yankho kumapangitsa kuti likhale losavuta.
Kuti tidziwe pH, tifunika kuchuluka kwa ma OH⁻ ions. Mwachitsanzo, tili ndi yankho la 0,1 M CH3COOK ndipo ionization constant ya acetic acid (Ka) ndi 1,8 × 10⁻⁵.
Masitepe omwe atengedwa ndi awa:
1. Kugwiritsa ntchito base constant (Kb) ya CH3COO⁻ ion:
\[ K_b = \frac{K_w}{K_a} = \frac{10^{-14}}{1,8 \times 10^{-5}} = 5,56 \times 10^{-10} \]
2. Lekanitsani ma ion a CH3COO⁻ mu yankho:
\[ K_b = \frac{[CH_3COOH][OH^-]}{[CH_3COO^-]} \]
Lolani kuti mlingo wa kulekanitsidwa ukhale 'x':
\[ 5,56 \nthawi 10^{-10} = \frac{x^2}{0,1-x} \]
Ponyalanyaza kachidutswa kakang'ono \(x\) mu denominator, titha kusavuta:
\[ x^2 \pafupifupi 5,56 \nthawi 10^{-11} \Rightarrow x = \sqrt{5,56 \nthawi 10^{-11}} = 7,45 \nthawi 10^{-6} \]
Kuchuluka kwa OH⁻:
\[ [OH^-] = 7,45 \nthawi 10^{-6} \]
pOH ya yankho:
\[ pOH = -\log [OH^-] = -\log (7,45 \times 10^{-6}) \pafupifupi 5,13 \]
Kugwiritsa ntchito ubale pakati pa pH ndi pOH:
\[ pH = 14 – pOH = 14 – 5,13 = 8,87 \]
Chifukwa chake, yankho la CH3COOK ndi losavuta ndipo pH yake ndi pafupifupi 8,87.
Funso 2: Hydrolysis ya Ammonium Chloride (NH4Cl)
Funso:
Kodi yankho la ammonium chloride (NH4Cl) ndi losauka, loyambira, kapena lopanda ndale? Lembani momwe hydrolysis imachitikira ndikupeza pH ya yankho.
Kukambirana:
Ammonium chloride (NH4Cl) ndi mchere wa asidi wamphamvu (HCl) ndi maziko ofooka (NH3). Kuchokera apa, tinganene kuti yankho lake ndi la asidi chifukwa ammonium ion (NH4⁺) imatha kusungunuka m'madzi.
Yankho lake ndi motere:
\[ NH_4^+ + H_2O \rightleftharpoons NH_3 + H_3O^+ \]
Ma ayoni a Ammonium (NH4⁺) amapereka ma protoni (H⁺) ku mamolekyulu amadzi (H2O) kuti apange ammonia (NH3) ndi ma ayoni a hydronium (H3O⁺). Kupezeka kwa ma ayoni a hydronium (H3O⁺) mu yankho ili kumapangitsa kuti yankho likhale ndi asidi.
Mwachitsanzo, tili ndi yankho la 0,1 M NH4Cl. Chokhazikika cha ionization (Kb) cha NH3 ndi 1,8 × 10⁻⁵.
Masitepe omwe atengedwa ndi awa:
1. Kugwiritsa ntchito asidi wosasintha (Ka) pa NH4⁺ ion:
\[ K_a = \frac{K_w}{K_b} = \frac{10^{-14}}{1,8 \times 10^{-5}} = 5,56 \times 10^{-10} \]
2. Lekanitsani ma ayoni a NH4⁺ mu yankho:
\[ K_a = \frac{[NH_3][H_3O^+]}{[NH_4^+]} \]
Lolani kuti mlingo wa kulekanitsidwa ukhale 'x':
\[ 5,56 \nthawi 10^{-10} = \frac{x^2}{0,1-x} \]
Ponyalanyaza kachidutswa kakang'ono \(x\) mu denominator, titha kusavuta:
\[ x^2 \pafupifupi 5,56 \nthawi 10^{-11} \Rightarrow x = \sqrt{5,56 \nthawi 10^{-11}} = 7,45 \nthawi 10^{-6} \]
Kuchuluka kwa H3O⁺:
\[ [H_3O^+] = 7,45 \nthawi 10^{-6} \]
pH ya yankho:
\[ pH = -\log [H_3O^+] = -\log (7,45 \times 10^{-6}) \pafupifupi 5,13 \]
Chifukwa chake, yankho la NH4Cl ndi acidic yokhala ndi pH pafupifupi 5,13.
Mu zitsanzo zonse ziwiri pamwambapa, tikuwona momwe kuzindikira mtundu wa hydrolysis kungathandizire kudziwa mtundu wa yankho. Pogwiritsa ntchito ionization equilibrium constant (Ka kapena Kb) ndi malingaliro ochepa osavuta, titha kuthetsa mavutowa mosavuta.
Kukambirana kumeneku kwa mavuto a hydrolysis ya mchere sikuti kumangophunzitsa luso losanthula pakuwerengera masamu komanso kumawonjezera kumvetsetsa kwa mfundo zoyambira za chemistry ya yankho. Kumvetsetsa momwe ma ayoni ochokera kosiyanasiyana amathandizira ma proton kapena ma acceptors ku mamolekyulu amadzi, komanso momwe izi zimakhudzira pH ya yankho, ndikofunikira kwambiri pakumvetsetsa mitu yambiri yapamwamba mu chemistry.
