Nā Kaulike Thermochemical: Ke Hoʻomaopopo ʻana i nā Kumumanaʻo Kumu o ka Energetics i nā Hana Kemika
Pendahuluan
ʻO ka Thermochemistry ka lālā o ke kemika e pili ana i nā loli ikehu, ʻoiai ka wela, i nā hopena kemika. He mea nui ka hoʻomaopopo ʻana i ka thermochemistry no nā noi ʻepekema a me nā ʻoihana he nui, me ka hoʻomohala ʻana i ka wahie, ka hana kemika, a me nā haʻawina hoʻololi aniau. E kūkākūkā kēia ʻatikala i nā kumumanaʻo kumu o ka thermochemistry, me ka nānā kūikawā ʻana i nā kaulike thermochemical, ʻo ia kahi manaʻo nui i ke aʻo ʻana i nā loli ikehu i nā hopena kemika.
Ka Wehewehena o ka Thermochemistry
ʻO ka Thermochemistry e pili ana i ke aʻo ʻana i nā loli ikehu e hele pū me nā hopena kemika a me nā loli o ke kūlana. ʻO kahi ʻano nui o ka thermochemistry pehea e hoʻololi ʻia ai ka ikehu ma ke ʻano o ka wela ma waena o kahi ʻōnaehana (nā mea hana a me nā huahana) a me kona puni i ka wā o kahi hopena kemika. Pono pinepine kēia i ka hoʻomaopopo ʻana i ke kānāwai mua o ka thermodynamics, kahi e ʻōlelo nei ʻaʻole hiki ke hana ʻia a luku ʻia paha ka ikehu, akā hiki ke hoʻololi wale i ke ʻano.
Ke Kānāwai Mua o ka Thermodynamics
ʻO ke kānāwai mua o ka thermodynamics, i ʻike ʻia hoʻi ʻo ke kānāwai o ka mālama ʻana i ka ikehu, e ʻōlelo ana:
\[ \Delta U = q + W \]
Ma kahi o \( \Delta U \) ka loli o ka ikehu kūloko o ka ʻōnaehana, ʻo \( q \) ka wela i hoʻohui ʻia i ka ʻōnaehana, a ʻo \( W \) ka hana i hana ʻia e ka ʻōnaehana. No kahi hopena kemika e hana ʻia ana ma ke kaomi mau, ʻo ka wela i hoʻohui ʻia a hoʻokuʻu ʻia paha (\( q_p \)) ua like ia me ka loli o ka enthalpy (\( \Delta H \)).
ʻO ka Enthalpy a me nā hopena kemika
ʻO ka Enthalpy (H) kahi huaʻōlelo i hoʻohana ʻia e wehewehe i ka ikehu holoʻokoʻa i loko o kahi ʻōnaehana, me ka ikehu kūloko a me ka ikehu e pono ai e noho i kahi ākea i loko o kahi ʻano i hāʻawi ʻia ma ke kaomi mau. ʻO ka loli o ka enthalpy (\( \Delta H \)) i ka wā o kahi hopena kemika e hāʻawi i kahi hōʻailona inā he exothermic (hoʻokuʻu i ka wela) a i ʻole endothermic (hoʻopili wela) ka hopena.
– Ka hopena exothermic: ʻAʻole maikaʻi ka \( \Delta H \), ʻo ia hoʻi, hoʻokuʻu ka ʻōnaehana i ka wela i nā mea a puni.
– Ka hopena endothermic: He maikaʻi ʻo \( \Delta H \), ʻo ia hoʻi ke omo nei ka ʻōnaehana i ka wela mai ke kaiapuni.
Nā Hoʻohālikelike Thermochemical
ʻO ka hoʻohālikelike thermochemical kahi hōʻike stoichiometric o kahi hopena kemika e komo pū ana me nā loli ikehu ma ke ʻano o ka enthalpy. Ua kākau ʻia kēia hoʻohālikelike penei:
\[ \text{Nā Mea Hana} \rightarrow \text{Nā Huahana} \quad \Delta H = \text{waiwai} \]
Eia kekahi laʻana, hiki ke kākau ʻia ka hopena puhi ʻana o ka methane penei:
ʻO ka huaʻōlelo ʻo "CH}_4(g)" + "O}_2(g)"
ʻO ka helu \(-890 \text{kJ}\) e hōʻike ana ua hoʻokuʻu ʻia he 890 kJ o ka ikehu i nā wahi a puni no kēlā me kēia mole o ka methane i puhi ʻia. He laʻana kēia o kahi hopena exothermic.
Enthalpy Maʻamau o ke Kūkulu ʻana
ʻO ka enthalpy maʻamau o ka hoʻokumu ʻana (\( \Delta H_f^\circ \)) ka loli enthalpy e hana ʻia ke hoʻokumu ʻia hoʻokahi mole o kahi hui mai nā mea i ko lākou mau kūlana maʻamau ma ke kaomi o 1 atm a me kahi mahana kikoʻī, maʻamau 25°C. He mea nui loa ka waiwai o \(\Delta H_f^\circ \) no ka hoʻoholo ʻana i ka loli enthalpy o nā hopena kemika paʻakikī me ka hoʻohana ʻana i ke kānāwai o Hess.
Ke Kānāwai o Hess
ʻŌlelo ke Kānāwai o Hess ua like ka loli enthalpy holoʻokoʻa o kahi hopena kemika me ka nānā ʻole i ke ala i lawe ʻia e ka hopena. ʻO ke ʻano kēia inā hiki ke puʻunaue ʻia kahi hopena i kekahi mau ʻanuʻu, a laila ʻo ka huina \(\Delta H \) ka huina o \(\Delta H \) o kēlā me kēia ʻanuʻu. Hiki ke kākau ʻia ke Kānāwai o Hess penei:
\[ \Delta H_{\text{holomua hopena}} = \sum \Delta H_{\text{ʻanuʻu}} \]
ʻO kahi laʻana maʻalahi o ke kānāwai o Hess ʻo ia ka hoʻoholo ʻana i ka \(\Delta H \) no ka hopena:
\[ \kikokikona{C(kiʻi)} + \frac{1}{2} \kikokikona{O}_2(g) \rightarrow \kikokikona{CO(g)} \]
me ka hoʻohana ʻana i ka ʻikepili aʻe:
1. \(\kikokikona{C(kiʻi)} + \kikokikona{O}_2(g) \rightarrow \kikokikona{CO}_2(g) \quad \Delta H = -393.5 \kikokikona{kJ}\)
2. \(\text{CO(g)} + \frac{1}{2} \text{O}_2(g) \rightarrow \text{CO}_2(g) \quad \Delta H = -283 \text{kJ}\)
Me kēia hoʻonohonoho hoʻohālikelike, ʻo ka loli enthalpy:
\[ \Delta H = (-393.5 \text{kJ}) – (-283 \text{kJ}) = -110.5 \text{kJ} \]
No laila, ʻo \(\Delta H \) no ka hoʻokumu ʻia ʻana o CO(g) mai ka graphite a me ka oxygen he \(-110.5 \text{kJ}\).
Ikehu Hoʻopaʻa
ʻO ka ikehu hoʻopaʻa ka ikehu e pono ai e uhaki i hoʻokahi mole o nā pilina i loko o kahi mole kinoea. ʻO ka ʻike o ka ikehu hoʻopaʻa e hiki ai iā mākou ke helu i ka loli enthalpy o kahi hopena kemika ma muli o ka helu a me nā ʻano o nā pilina i haki a hoʻokumu ʻia. No ka laʻana, i ka hopena ʻokiʻoki o kahi mole hydrogen (\(\text{H}_2 \rightarrow 2\text{H}\)), inā ʻo ka ikehu hoʻopaʻa o H-H he 436 kJ/mol, a laila pono 436 kJ e uhaki i hoʻokahi mole o \(\text{H}_2\).
Nā noi o nā kaulike Thermochemical
ʻAʻole wale nā hoʻohālikelike thermochemical he mea nui i nā keʻena hoʻokolohua kemika, akā i nā ʻano hana like ʻole.
1. ʻOihana Ikehu: Ke hoʻomaopopo nei i ka ikehu o ka puhi ʻana i nā wahie mōʻalihaku a me ka biomass.
2. ʻEnekinia Kemika: Ke hoʻolālā ʻana i nā mea hana kemika, e hoʻomaikaʻi ana i nā kūlana hana no ka pono o ka ikehu.
3. Ola kino a me ka lāʻau lapaʻau: Ke hoʻolālā ʻana i nā lāʻau lapaʻau e pili ana i nā loli ikehu i ke kūkulu ʻia ʻana a me ka haki ʻana o nā pūhui kemika.
4. Kaiapuni: Ke hoʻomaopopo ʻana a me ka hōʻemi ʻana i nā hopena ikehu o nā kaʻina hana ʻoihana i ka loli o ke aniau.
Ka hopena
Hāʻawi ka Thermochemistry i kahi ʻōnaehana ikaika no ka hoʻomaopopo ʻana a me ka wānana ʻana i nā loli ikehu i nā hopena kemika. Ma ka hoʻohana ʻana i nā kaulike thermochemical, hiki iā mākou ke helu i nā loli enthalpy a wānana inā he endothermic a exothermic paha kahi hopena. ʻO ka hoʻohana ʻana o ka thermochemistry ma nā ʻano like ʻole e hōʻike ana i ke koʻikoʻi o ka hoʻomaopopo ʻana i kēia mau loli ikehu i ke ola o kēlā me kēia lā a me ka ʻoihana hou. I ka wā e hiki mai ana, e hilinaʻi nui ka hoʻomohala ʻana o nā ʻenehana hoʻomau i nā loina kumu i aʻo ʻia e ka thermochemistry.
