Me pēhea te tatau i te kukū o te otinga
Ko te kukū o te otinga tētahi o ngā kaupapa tino taketake me te mea nui i roto i te matū, mō ngā taiwhanga kura, rangahau taiwhanga, me ngā tono ahumahi pēnei i te rongoā, te kai, me te maimoatanga wai. He māmā noa iho, ko te kukū e tohu ana i te nui o te matū matū kei roto i tētahi nui o te matū ...
1. Mārama ki ngā Kupu Taketake: te Wairewa, te Wairewa, me te Otinga
I mua i te tīmatanga o ngā tatau, kia tino wehewehea e koe ngā kupu e toru e whai ake nei:
– Wairewa: he matū kua rewa, hei tauira te huka, te tote, te HCl rānei.
– Kaiwhakarewa: he matū ka rewa, ko te nuinga he wai (H₂O) i te nuinga o te wā.
– Otinga: he ranunga ōrite o te wairewa me te wai whakarewa.
I te tatau i te kukū, ko te mea e whakamahia pinepine ana ko te nui o te matū rewa (papatipu, mole, rōrahi rānei) e whakaritea ana ki te rōrahi o te wairewa, ki te papatipu rānei o te wairewa.
2. Ngā Momo Arotahi Noa
Anei ētahi o ngā waeine, ngā huarahi rānei e whakamahia whānuitia ana hei whakaatu i te kukū:
1. Te Molarity (M)
2. Te Molarity (m)
3. Ōrau papatipu (% w/w)
4. Ōrau rōrahi (% v/v)
5. Ōrau papatipu-rōrahi (% w/v)
6. Ngā wāhanga mō ia miriona (ppm) me ngā wāhanga mō ia piriona (ppb)
7. Te Noa (N) (e whakamahia tonutia ana i roto i ētahi kaupapa pēnei i te titration)
Nā te mea he horopaki whakamahinga motuhake tō ia tauira, me mōhio koe ki te tātai, ki ngā raraunga e hiahiatia ana, me pēhea hoki te huri.
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3. Te Tātai i te Molarity (M)
Ko te molarity e whakaatu ana i te maha o ngā mole o te matū solute mō ia rita o te otinga.
Tātai:
\[
M = \frac{n}{V}
\]
Ngā Mōhiohio:
– \( M \) = te mōroiti (mol/L)
– \( n \) = te maha o ngā mole o te matū wairewa (mol)
– \( V \) = te rōrahi o te otinga (L)
Ngā taahiraa tatau i te molarity
1. Tātaihia ngā mole ngā matū rewa:
\[
n = \frac{m}{M_r}
\]
– \( m \) = te papatipu o te matū (karamu)
– ( M_r ) = papatipu molar (g / mol)
2. Tahurihia te rōrahi o te otinga ki ngā rita mēnā kei roto tonu i te mL:
\[
1000 mL = 1 L
\]
3. Whakauruhia ki te tātai molarity.
Tauira:
Whakarewahia te 5,85 karamu o te NaCl (Mr = 58,5 g/mol) ki te rōrahi otinga o te 500 mL. Tātaihia te molarity.
– Mol NaCl:
\[
n = \frac{5,85}{58,5} = 0,1 \text{ mol}
\]
– Te rahinga o te otinga:
\[
500 mL = 0,5 L
\]
– Te Molarity:
\[
M = \frac{0,1}{0,5} = 0,2 \text{ M}
\]
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4. Te Tātai i te Molality (m)
Ko te molality e tohu ana i te maha o ngā mole o te solute mō ia kirokaramu o te whakarewa. He mea whakamahi pinepine tēnei i roto i te ako i ngā āhuatanga colligative (te ira kohua, te ira tio, te pēhanga osmotic) nā te mea kāore e pā ki te pāmahana (kāore te papatipu e rerekē pērā i te rōrahi).
Tātai:
\[
m = \frac{n}{papatipu\ whakarewa\ (kg)}
\]
Tauira:
Ka whakarewaina te 10 karamu o te urea (Mr = 60 karamu/mol) ki roto i te 200 karamu o te wai. Tātaihia te molality.
– Te mol urea:
\[
n = \frac{10}{60} = 0,1667 \text{ mol}
\]
– Te taumaha o te whakarewa:
\[
200 karamu = 0,2 karamu
\]
– Te Molarity:
\[
m = \frac{0,1667}{0,2} = 0,8335 \text{ m}
\]
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5. Te Tātai i te Ōrau Papatipu (% w/w)
Ka whakamahia te ōrau papatipu ina he mea nui ake te hanganga e hangai ana ki te papatipu, hei tauira i roto i ngā ranunga totoka, i ngā otinga kukū rānei.
Tātai:
\[
\% (w/w) = \frac{papatipu\ o te matū wairewa}{papatipu\ o te wairewa} \whakanuia ki te 100\%
\]
Tauira:
Ka hangaia he otinga mai i te 10 karamu o te tote me te 90 karamu o te wai. He aha te ōrau papatipu o te tote?
– Te papatipu o te wairewa = 10 karamu + 90 karamu = 100 karamu
– Ōrau papatipu:
\[
\% = \frac{10}{100} \whakareatia ki te 100\% = 10\%
\]
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6. Te Tātai i te Ōrau o te Rōrahi (% v/v)
E whakamahia whānuitia ana te ōrau rōrahi mō ngā ranunga wai-wai, hei tauira, te waipiro i roto i te wai.
Tātai:
\[
\% (v/v) = \frac{rōrahi\ matū\}{rōrahi\ otinga} \whakareatia ki te 100\%
\]
Tauira:
Ka whakaranua he 30 mL o te etanoru, kātahi ka whakaranua kia 100 mL te rahinga o te wairewa. He aha te % v/v?
\[
\% (v/v) = \frac{30}{100} \times 100\% = 30\%
\]
He kōrero nui: i roto i ētahi ranunga, kāore ngā rōrahi i te tino tāpirihia (nā te whakawhāititanga o te rōrahi), engari mō ngā raruraru taketake ka kiia he tāpirihia.
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7. Te Tātai i te Ōrau Papatipu-Rōrahi (% w/v)
He mea tino kitea tēnei waeine i ngā tapanga otinga i roto i te koiora, i te hauora rānei, hei tauira "NaCl 0,9% w/v", arā, 0,9 karamu NaCl mō ia 100 mL o te otinga.
Tātai:
\[
\% (w/v) = \frac{papatipu\ (g)}{rōrahi\ otinga\ (mL)} \whakanuia ki te 100\%
\]
Tauira:
Mena ka rewahia te 2 karamu o te hukahuka ki te rōrahi o te 50 mL, kātahi:
\[
\% (b/v) = \frac{2}{50} \times 100\% = 4\%
\]
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8. Te tatau i te ppm me te ppb
E whakamahia ana te ppm (ngā wāhanga mō ia miriona) mō ngā kukū iti rawa, hei tauira te nui o ngā poke i roto i te wai.
Mō ngā otinga wai (kiato ~1 g/mL):
– 1 ppm ≈ 1 mg/L
– 1 ppb ≈ 1 µg/L
Tauira ppm:
Mena he 5 mg o te matū X kei roto i te 2 rita o te wai, ko te kukū ko:
\[
\text{ppm} = \frac{5\ mg}{2\ L} = 2,5\ mg/L \approx 2,5\ ppm
\]
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9. Te Whakarewatanga o te Otinga: Tātai M1V1 = M2V2
He maha ngā wā ka whai koe i tētahi otinga rakau kukū, ā, e hiahia ana koe ki te whakawaiwai. I roto i te whakawaiwai, ka noho tonu te maha o ngā mole o te matū wairewa i mua me muri i te whakawaiwai (mēnā kāore he tauhohenga).
Tātai waimeha:
\[
M_1V_1 = M_2V_2
\]
Ngā Mōhiohio:
– \( M_1 \) = te kukū tīmatanga
– \( V_1 \) = rōrahi i tangohia mai i te otinga tīmatanga
– \( M_2 \) = kukū whakamutunga
– \( V_2 \) = te rōrahi whakamutunga o te otinga i muri i te waimehatanga
Tauira:
E 2 M HCl tāu, ā, e hiahia ana koe ki te hanga i te 250 mL o te 0,5 M HCl. E hia te rōrahi o te 2 M HCl e hiahiatia ana?
\[
V_1 = \frac{M_2 V_2}{M_1} = \frac{0,5 \times 250}{2} = 62,5\ mL
\]
Arā, tangohia te 62,5 mL o te otinga 2 M, kātahi ka tāpirihia he wai kia tae ki te rōrahi katoa o te 250 mL.
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10. Ngā Tohutohu hei Whakamātautau i te Hē o ngā Tātaitanga Kukū
1. Kia tūpato ki ngā waeine: me huri te mL ki te L mō te molarity; te g ki te kg mō te molality.
2. Wehewehea te "whakarewa" me te "whakaoti": ka whakamahia e te molarity te rōrahi o te otinga, ka whakamahia e te molality te papatipu o te whakarewa.
3. Whakamahia te papatipu molar tika: tirohia te tātai matū me te maha o ngā ngota.
4. Kaua e wareware ki te papatipu/rahinga katoa o te otinga: mō ngā ōrau, ko te tauwehenga ko te papatipu/rahinga o te otinga, ehara i te whakarewa.
5. Tuhia ngā kaupae me ngā waeine i ia wāhanga: koinei te huarahi tino whai hua hei ārai i ngā hapa.
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Whakamutunga
Ehara i te mea uaua te tatau i te kukū o tētahi otinga mēnā ka mārama koe ki ngā momo kukū e whakamahia ana me ngā raraunga e wātea ana. He pai te molarity mō ngā tataunga e hangai ana ki te tauhohenga me te otinga i roto i te taiwhanga, he pai te molality mō ngā āhuatanga colligative, he maha ngā wā ka whakamahia te ōrau papatipu/rōrahi i roto i ngā mahi ahumahi me te hauora, ko te ppm/ppb ia ka whakamahia mō ngā kukū iti rawa. Mā te mōhio ki ngā tātai taketake pēnei i te \( M = n/V \), te molality, te ōrau, me te waimeha \( M_1V_1 = M_2V_2 \), ka taea e koe te whakaoti tere me te tika i ngā raruraru kukū.
Ki te hiahia koe, ka taea e au te hanga i tētahi pepa tātai tere (pepa tinihanga) me ngā pātai whakaharatau me ngā whakamārama.
