Ngā Tauira Pātai me te Kōrero mō te Waikawa-Pūtake a Lewis
Pendahuluan
He kaupapa matua ngā tauhohenga waikawa-pūtake i roto i te matū, ā, he whānui te whakamahinga i roto i ngā momo marautanga me ngā ahumahi. He maha ngā whakamāramatanga o ngā waikawa me ngā pūtake e whakamahia ana i roto i te matū, tae atu ki ngā whakamāramatanga a Arrhenius, Bronsted-Lowry, me Lewis. Ka arotahi tēnei tuhinga ki te ariā o ngā waikawa me ngā pūtake a Lewis, ā, ka whakaratohia he tauira raruraru me ngā kōrero hei whakamārama ake i ēnei ariā.
Te Whakamāramatanga o ngā Waikawa me ngā Kawenga Lewis
I mua i te urunga atu ki ngā tauira pātai, he mea tino nui kia mārama tuatahi ki ngā whakamāramatanga taketake o ngā waikawa me ngā kawakore e ai ki te ariā a Lewis.
– Waikawa Lewis: He matū ka taea te tango i tētahi takirua irahiko.
– Pūtake Lewis: He matū ka taea te tuku i tētahi takirua irahiko.
He māmā noa iho, ko te waikawa Lewis he pūhui he maha ngā porowhita kau ka taea te whakakī e ngā takirua irahiko, ko te turanga Lewis ia he pūhui he maha ngā takirua irahiko kore utu ka taea te tuku ki te waikawa.
Ngā Tauira o ngā Waikawa me ngā Kawenga Lewis
– Ngā waikawa Lewis: Konumohe pūhaumāota (AlCl₃), Boron trifluoride (BF₃), Ferric chloride (FeCl₃), me ētahi atu.
– Ngā turanga Lewis: Haukini (NH₃), Wai (H₂O), Katote hauota (Cl⁻), me ētahi atu.
Ngā Pātai Tauira me te Kōrero
Pātai 1
Whakatauhia ko tēhea te mea e mahi ana hei waikawa Lewis me te turanga Lewis i roto i te tauhohenga e whai ake nei:
\[ \text{AlCl}_3 + \text{NH}_3 \rightarrow \text{AlCl}_3\text{NH}_3 \]
Kōrero:
– Konumohe pūhaumāota (\( \text{AlCl}_3 \)): He porowhita kau tō te konumohe i roto i te AlCl₃ ka taea te tango i tētahi takirua irahiko mai i te takirua irahiko takitahi i runga i te hauota i roto i te NH₃.
– Haukinia (\( \text{NH}_3 \)): He takirua irahiko takitahi tō te haukinia ka taea e ia te tuku ki te konumohe.
Nā, i roto i tēnei tauhohenga:
– Ka mahi a \( \text{AlCl}_3 \) hei waikawa Lewis.
– Ko \( \text{NH}_3 \) te pūtake o Lewis.
Pātai 2
Tāutuhia te waikawa Lewis me te turanga Lewis i roto i te tauhohenga e whai ake nei:
\[ \kuputuhi{BF}_3 + \kuputuhi{F}^- \rightarrow \kuputuhi{BF}_4^- \]
Kōrero:
– Boron trifluoride (\( \text{BF}_3 \)): He porowhita kau tō te boron i roto i te BF₃ ka taea te tango i tētahi takirua irahiko mai i te katote fluoride (F⁻).
– Katote pūhaumāota (\( \text{F}^- \)): He takirua irahiko takitahi tō te katote pūhaumāota ka taea te tuku ki te pōroni.
Nā, i roto i tēnei tauhohenga:
– Ka mahi a \( \text{BF}_3 \) hei waikawa Lewis.
– Ka mahi a \( \text{F}^- \) hei turanga Lewis.
Pātai 3
I roto i te taunekeneke i waenganui i a \( \text{FeCl}_3 \) me \( \text{H_2O} \), tautuhia ko tēhea e mahi ana hei waikawa Lewis me tēhea e mahi ana hei turanga Lewis.
Kōrero:
– Ko te konupora ferric (\( \text{FeCl}_3 \)): He ngota rino (Fe) tō te konupora ferric me te porowhita kau e taea ai te tango i te takirua irahiko mai i te wai.
– Wai (\( \text{H₂O} \)): He takirua irahiko takitahi kei te ngota hāora o te wai ka taea te tuku ki te rino.
Nā, i roto i tēnei tauhohenga:
– Ka mahi a \( \text{FeCl}_3 \) hei waikawa Lewis.
– Ka mahi a \( \text{H₂O} \) hei turanga Lewis.
Pātai 4
Ka taea e ngā ngota waro hauhā (CO₂) te mahi hei waikawa Lewis? Homai ngā take i runga i tō rātou hanganga ngota.
Kōrero:
Hei whakautu i tēnei pātai, me whai tātaritanga hiko tātou o te ngota CO₂. He rārangi te hanganga o te ngota CO₂, me te hononga takirua o te ngota waro ki ngā ngota hāora e rua (O=C=O).
– Te hauhā waro (CO₂): Ahakoa he takirua irahiko takitahi tōna, he iti noa iho ngā irahiko o te ngota waro i roto i te CO₂ nā te mea ka kukumea te nuinga o te kiato irahiko e ngā hononga takirua e rua me te hāora mai i te waro. He porowhita kau kei waenganui o te ngota waro o tēnei hanganga ngota e āhei ai ia ki te tango i tētahi takirua irahiko.
Nō reira, ka taea e te CO₂ te mahi hei waikawa Lewis nā te mea ka taea e ia te tango i tētahi takirua irahiko, ā, ka tutuki ai ngā paearu mō tētahi waikawa Lewis.
Pātai 5
Whakatauhia mēnā ko te BF₃ me te NH₃ i roto i te tauhohenga e whai ake nei he waikawa, he kawa rānei a Lewis:
\[ \text{BF}_3 + \text{NH}_3 \rightarrow \text{BF}_3\text{NH}_3 \]
Kōrero:
– Te toru-fluoride o te boron (\(BF_3 \)) : He hanganga o ngā fluoro e toru kei te taha o te boron te BF₃. E ono ngā irahiko valence e karapotia ana te ngota boron mai i te here BF, he iti iho i te octet (8 ngā irahiko). Nā tēnei ka noho he porowhita kau o te BF₃ i runga i te boron ka taea te tango i te takirua irahiko mai i te NH₃.
– Haukini (\( NH_3 \)) : He takirua irahiko takitahi tō te NH₃ i runga i te ngota hauota.
I roto i tēnei tauhohenga:
– Ka mahi a \( \text{BF}_3 \) hei waikawa Lewis.
– Ko \( \text{NH}_3 \) te pūtake o Lewis.
Pātai 6
Tāutuhia ngā takirua waikawa me ngā takirua turanga Lewis i roto i ngā tauhohenga e whai ake nei, ā, whakamāramahia ō whakaaro:
\[ \text{NH}_3 + \text{H}^+ \rightarrow \text{NH}_4^+ \]
Kōrero:
– Haukini (\( NH_3 \)) : He takirua irahiko takitahi kei runga i te ngota hauota o te NH₃ ka taea te tuku.
– Hauwai iona (\( H^+ \)) : He pūrotene te H⁺, kāore he irahiko, nō reira he kaiwhiwhi takirua irahiko.
I roto i tēnei tauhohenga:
– Ka mahi a \( \text{NH}_3 \) hei turanga Lewis nā te mea ka tukuna e ia he takirua irahiko.
– Ka mahi a \( \text{H}^+ \) hei waikawa Lewis nā te mea ka whakaaetia he takirua irahiko.
Whakamutunga
Mā te ariā waikawa-pūtake a Lewis ka whānui ake tō tātou tirohanga ki ngā tauhohenga matū mā te whakaaro ehara i te mea ko ngā pūrotana anake engari ko ngā taunekeneke i waenga i ō rātou takirua irahiko. He mea nui te māramatanga hōhonu ki tēnei ariā i roto i te matū hei tātari me te matapae i te whanonga o ngā momo pūhui. Mā roto i ngā tauira me ngā kōrero i runga ake nei, kua kite tātou i te āhua o te tautuhi i ngā waikawa me ngā pūtake a Lewis i roto i te mahi. Ehara i te mea he mea taketake noa iho tēnei ariā engari he maha hoki te whakamahinga i roto i te rangahau matū me te ahumahi.
Mā te mōhio ko ēhea ngā matū e mahi ana hei waikawa, hei turanga rānei a Lewis i roto i tētahi tauhohenga motuhake ka āwhina i a tātou ki te mārama ake ki ngā tikanga tauhohenga me te hanga i ngā whakamātautau whai hua ake. Nō reira, ko te māramatanga pai me te mahi tonu ngā mea nui ki te matatau ki tēnei ariā.
