Nā Kānāwai Thermochemical ma ke Kino
He lālā ʻepekema ka Thermochemistry e aʻo ana i ka pilina ma waena o nā hopena kemika (a i ʻole nā loli kino i loko o kahi mea) a me ka ikehu wela e hele pū ana (wela). Ma ke ʻano o ka physics, lawelawe ka thermochemistry ma ke ʻano he alahaka koʻikoʻi ma waena o nā manaʻo o ka ikehu, ka wela, ka hana, a me nā loli i ke ʻano o ka mea. Ke hana ʻia kahi hopena, ʻaʻole loa e "ʻike ʻia" a "nalowale" paha ka ikehu me ka ʻole o kahi kaha. Hoʻololi wale ka ikehu i ke ʻano: mai ka ikehu kemika i ka wela, a i ʻole ka ʻaoʻao ʻē aʻe - ua omo ʻia ka wela e hoʻokele i nā loli kemika. Ua hōʻuluʻulu ʻia nā kumumanaʻo e hoʻomalu ana i kēia ma nā kānāwai o ka thermochemistry, kahi e hana ai i ke kumu no ka helu ʻana i nā wela o ka hopena, ka pono o ka ikehu, a me ka hoʻolālā ʻōnaehana ʻoihana.
Nā Manaʻo Kumu: Nā ʻŌnaehana, nā Kaiapuni, a me ka Wela o ka Pane
No ka hoʻomaopopo ʻana i nā kānāwai o ka thermochemistry, ʻo ka mea mua e hoʻomaopopo ai, ʻo ia ka wehewehe ʻana o ka ʻōnaehana a me nā mea e puni ana. ʻO ka ʻōnaehana ka ʻāpana o ke ao holoʻokoʻa a mākou e aʻo nei—no ka laʻana, nā mea e hana ana i loko o kahi ipu. ʻO nā mea e puni ana nā mea āpau ma waho o ka ʻōnaehana. ʻO ka hoʻololi ikehu ma waena o kahi ʻōnaehana a me kona mau mea e puni ana e hana pinepine ʻia ma ke ʻano o ka wela.
ʻO ka wela o ka hopena e hōʻike pinepine ʻia ma ke ʻano he loli o ka enthalpy, i hōʻailona ʻia e ΔH. ʻO Enthalpy kahi nui thermodynamic e hōʻike ana i ka "ʻike ikehu" o kahi ʻōnaehana ma ke kaomi mau, a he mea pono loa ia no ka mea he nui nā hopena e hana ʻia ma ke kaomi lewa. Ma ke ʻano laulā:
– Inā hoʻokuʻu ka ʻōnaehana i ka wela i nā mea a puni, he exothermic ka hopena a he maikaʻi ʻole ʻo ΔH (ΔH < 0). - Inā omo ka ʻōnaehana i ka wela mai nā mea a puni, he endothermic ka hopena a he maikaʻi ʻo ΔH (ΔH > 0).
ʻO kahi laʻana maʻalahi o ka hopena exothermic ka puhi ʻana o ka wahie, ʻoiai ʻo kahi laʻana o ka hopena endothermic ke kaʻina hana o ka photosynthesis (kahi e pono ai ka ikehu mai ka lā).
ʻO ke Kānāwai o ka Mālama ʻana i ka Ikehu ma ke ʻano he Kumu o ka Thermochemistry
Ma hope o nā kānāwai āpau o ka thermochemistry aia kahi kumumanaʻo nui o ka physics: ke Kānāwai o ka Mālama ʻana i ka Ikehu, ʻo ia ke kumu o ke Kānāwai Mua o Thermodynamics. Ke ʻōlelo nei kēia kānāwai ʻaʻole hiki ke hana ʻia a luku ʻia paha ka ikehu, akā hiki ke hoʻololi ʻia ke ʻano. Ma ka hōʻailona thermodynamic, pili ka loli o ka ikehu kūloko (ΔU) i ka wela (Q) a me ka hana (W) e:
ΔU = Q − W
Hiki ke ʻokoʻa ka hōʻailona a me ka wehewehe ʻana o ka hana ma muli o ke kuʻuna, akā like ka manaʻo nui: inā loaʻa i kahi ʻōnaehana ka wela, e piʻi aʻe kona ikehu kūloko; inā hana ka ʻōnaehana ma nā mea a puni, e emi ana kona ikehu kūloko. I nā hihia thermochemical he nui—ʻoi aku hoʻi ma ke kaomi mau—hoʻohana pinepine ʻia ka enthalpy (H), no laila ua like ka wela ma ke kaomi mau me ΔH.
Me kēia kumu, ʻike ka thermochemistry i nā hopena ʻaʻole wale ma ke ʻano he loli i nā mea, akā, he mau loli i ka ikehu e hiki ke helu pono ʻia.
Ke Kānāwai o Hess: ʻAʻole kūʻokoʻa ke Ala o ka Wela o ka Pane
ʻO kekahi o nā kānāwai koʻikoʻi o ka thermochemistry ʻo ke kānāwai o Hess. Ke ʻōlelo nei kēia kānāwai e pili ana ka loli enthalpy holoʻokoʻa o kahi hopena i nā kūlana mua a me ka hope, ʻaʻole ma ke ala hopena. ʻO ke ʻano kēia inā hiki ke hana ʻia kahi hopena ma kekahi mau ʻanuʻu, ʻo ka nui o ka wela (ΔH) i hana ʻia a i omo ʻia paha e like me ka wela o ka hopena pololei, inā like nā mea hana a me nā huahana hope loa.
Ma ke ʻano makemakika, inā hiki ke hoʻokaʻawale ʻia ka hopena A → B i:
– A → C (ΔH₁)
– C → B (ΔH₂)
pēlā:
Huina ΔH = ΔH₁ + ΔH₂
He mea pono ke Kānāwai o Hess no ka mea he nui nā hopena he paʻakikī ke ana pololei i ko lākou wela o ka hopena. Ma ka wāwahi ʻana i ka hopena i nā ʻanuʻu no ka loaʻa ʻana o ka ʻikepili, hiki iā mākou ke helu pololei iā ΔH. I loko o ka physics i hoʻopili ʻia a me ka ʻoihana, kōkua kēia kānāwai i ka wānana ʻana i nā koi ikehu o nā kaʻina hana kemika, e like me ka hana ʻana o ka ammonia, ka hoʻomaʻemaʻe ʻana i ka metala, a me nā hopena i loko o nā pila.
Ke Kānāwai Lavoisier-Laplace: Loaʻa i nā hopena hoʻohuli he ΔH o ka hōʻailona kū'ē
ʻO kekahi kānāwai thermochemical koʻikoʻi ʻo ia ke Kānāwai Lavoisier-Laplace, kahi e ʻōlelo nei ua like ka nui o ka wela o ka hopena o kekahi kaʻina hana akā ua kū'ē i ka wela o ka hopena hope. I nā huaʻōlelo ʻē aʻe:
Inā ka hopena:
Loaʻa iā A → B ʻo ΔH = x,
a laila ka hopena hope:
ʻO B → Loaʻa iā A ʻo ΔH = −x.
Me he mea lā maʻalahi kēia kumumanaʻo, akā he mea nui ia. Ke hōʻoia nei ia e hahai ana nā loli ikehu i kahi symmetry kūlana: inā hoʻokuʻu ʻia kahi nui o ka ikehu mai A a i B, a laila pono e omo ʻia ka nui like o ka ikehu e hoʻi ai mai B a i A. Hoʻohana ʻia kēia kumumanaʻo i ka nānā ʻana i nā pōʻaiapuni ikehu, me nā mīkini wela, nā ʻōnaehana hoʻomaʻalili, a me nā helu ʻana o nā ikehu pili i loko o nā molekala.
ʻEnthalpy o ke Kūkulu ʻana a me ka Enthalpy o ke Puhi ʻana
No ka hoʻomaʻalahi ʻana i nā helu thermochemical, ua wehewehe nā kānaka ʻepekema i kekahi mau ʻano o nā enthalpies maʻamau:
1. Enthalpy maʻamau o ka hoʻokumu ʻana (ΔHf°)
ʻO kēia ka loli enthalpy ke hoʻokumu ʻia 1 mole o kahi hui mai kona mau mea ma lalo o nā kūlana maʻamau (ʻo ka maʻamau he 1 atm a me 25°C). ʻO kēia waiwai ka "poloka kūkulu" i ka helu ʻana i ka ΔH o kahi hopena.
2. Enthalpy maʻamau o ke kuni ʻana (ΔHc°)
ʻO ia ka loli enthalpy ke puhi ʻia ka 1 mole o kahi mea i ka oxygen. ʻO ka lapalapa ʻana he exothermic, no laila ʻo ΔHc° ka mea maʻamau he maikaʻi ʻole.
Me ka ʻikepili enthalpy o ka hoʻokumu ʻana, hiki ke helu ʻia ka loli enthalpy o ka hopena ma o:
ΔHreaction = Σ(ΔHf° huahana) − Σ(ΔHf° mea hoʻohui)
Hoʻohana pinepine ʻia kēia ʻano hana i ka kemika kino a me ka physics kemika, ʻoiai ke aʻo ʻana i nā hopena ma lalo o nā kūlana kokoke i ke kūlana maʻamau.
Calorimetry: Pehea e ana ai i ka wela o ka hopena
ʻAʻole wale nā kānāwai o ka thermochemistry he kumumanaʻo akā hiki ke hoʻāʻo ʻia ma ke ʻano hoʻokolohua. ʻO ke ʻano hana mua no ke ana ʻana i ka wela o ka hopena he calorimetry, ʻo ia ke ana ʻana o ka hoʻololi wela me ka hoʻohana ʻana i ka calorimeter.
I loko o kahi hoʻokolohua calorimetry maʻalahi, ʻo ka wela i hoʻokuʻu ʻia a i ʻole i omo ʻia e kahi hopena e hoʻololi i ka mahana o ka wai a puni a i ʻole nā mea ʻē aʻe. ʻO ka pilina kumu:
Q = mc ΔT
me:
– Q = wela (Joules)
– m = nuipaʻa (kg a i ʻole g)
– c = wela kikoʻī (J/kg·K a i ʻole J/g·°C)
– ΔT = loli o ka mahana
I loko o kahi calorimeter bomb, hana ʻia ka hopena kuni i loko o kahi pahu pani, e mālama ana i kahi leo mau. ʻOi aku ka pili o kēia i ka loli o ka ikehu kūloko (ΔU), akā hiki ke hoʻololi ʻia i ΔH inā pono.
Pili i ka Physics a me ke ola maoli
He hopena nui ko ka Thermochemistry i ka physics i hoʻopili ʻia. Ma ke kahua ikehu, kōkua ia i ka hoʻoholo ʻana i ka waiwai calorific o nā wahie, he mea nui ia no ka hana mana, nā mīkini kaʻa, a me ka loiloi pono o ka ikehu. Ma ka ʻepekema mea, wehewehe ka thermochemistry i ke kumu e pono ai kekahi mau hopena i ka hana ʻana i ka sima, kila, a i ʻole nā ceramic i nā mahana kiʻekiʻe a me ka nui o ka ikehu. Ma ke kahua kaiapuni, pili ka helu ʻana i nā wela o ke kuni ʻana i nā hoʻokuʻu kinoea ʻōmaʻomaʻo a me nā hoʻolālā e hōʻemi i ka hopena o ka hoʻomehana honua.
ʻOiai i loko o ka biology, wehewehe ka thermochemistry pehea e loaʻa ai i ke kino ka ikehu mai ka meaʻai ma o nā hopena metabolic ʻo ia hoʻi nā hopena kemika exothermic i kāohi ʻia.
Pani
ʻO nā kānāwai o ka thermochemistry i ka physics e hōʻike ana e pili mau ana nā hopena kemika a me nā loli kino me nā loli ikehu hiki ke ana ʻia. Ma muli o ka mālama ʻana i ka ikehu, ke kānāwai o Hess, a me ke kānāwai Lavoisier-Laplace, hiki iā mākou ke helu a wānana i nā wela o ka hopena, no ka hoʻomaopopo ʻana i nā hanana kūlohelohe a me ka hoʻolālā ʻana i nā kaʻina hana ʻoihana. ʻAʻole wale ka Thermochemistry he hōʻiliʻili o nā formula, akā he kuanaʻike ʻepekema e hōʻike ana i kēlā me kēia loli i ka mea he "kumukūʻai" ikehu a i ʻole "hua." ʻO ka hoʻomaopopo ʻana i kēia mau kānāwai ʻo ia hoʻi ka hoʻomaopopo ʻana i kekahi o nā kumu kumu o ka launa pū ʻana ma waena o ka mea a me ka ikehu ma ke ao holoʻokoʻa.
Inā makemake ʻoe, hiki iaʻu ke hoʻohui i kahi laʻana o ka helu ʻana iā ΔH me ka hoʻohana ʻana i ke Kānāwai o Hess a i ʻole ka ʻikepili ΔHf°, me nā ʻanuʻu.
