[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-109-1-fire-science-033":3},{"subject":4,"subjectSlug":5,"subjectKicker":6,"subjectShort":7,"question":8,"related":27,"sameNumber":52,"hasEssay":26},"火災學概要","fire-science","火災學 · Fire Science","火災學",{"id":9,"webId":10,"year":11,"session":12,"subject":4,"number":13,"stem":14,"options":15,"answer":20,"answerNote":21,"images":22,"imagesPending":23,"lawTimestamp":11,"explanation":24,"explanationDeep":25,"freq":12,"indexable":26},"fire-109-1-火災學概要-033","fire-109-1-fire-science-033",109,1,33,"乙醇之燃燒化學反應式為下列何者？ 9 3",{"A":16,"B":17,"C":18,"D":19},"C3H6+ O2 →3CO2+3H2O","CH3OH+ O2 →CO2+2H2O 2 2","C2H5OH+3O2 →2CO2+3H2O","C2H5OC2H5+6O2 →4CO2+5H2O","C",null,[],false,"本題考點：完全燃燒化學反應式的配平，以及乙醇分子式 C₂H₅OH 的辨識。\n【正解理由】乙醇分子式為 C₂H₅OH，每個分子含 2 個碳、6 個氫與 1 個氧。完全燃燒時碳全數生成 CO₂、氫全數生成 H₂O，故生成物為 2CO₂＋3H₂O；生成物側氧原子總數為 2×2＋3＝7 個，扣除乙醇本身自帶的 1 個氧原子，尚需由氧氣供應 6 個氧原子，即 3 莫耳 O₂。配平結果為 C₂H₅OH＋3O₂→2CO₂＋3H₂O，故選 C。\n【逐項排除】\n(A) 錯誤。C₃H₆ 為丙烯，屬烯類而非醇類，碳數 3、且分子不含氧，其燃燒式與乙醇無關。\n(B) 錯誤。CH₃OH 為甲醇，碳數僅 1，生成物為 CO₂＋2H₂O，雖與乙醇同屬醇類同系物，分子式並不相同。\n(C) 正確。反應物確為乙醇，且左右兩側碳為 2、氫為 6、氧為 7，三種原子數皆平衡。\n(D) 錯誤。C₂H₅OC₂H₅ 為乙醚，碳數為 4，生成物為 4CO₂＋5H₂O，屬醚類而非醇類。\n【演算步驟】\n① 設 C₂H₅OH＋aO₂→bCO₂＋cH₂O。\n② 碳平衡：b＝2；氫平衡：6＝2c，得 c＝3。\n③ 氧平衡：左側 1＋2a＝右側 2b＋c＝2×2＋3＝7，得 a＝3。\n④ 故 C₂H₅OH＋3O₂→2CO₂＋3H₂O。\n【記憶點】乙醇兩個碳，係數依序 1、3、2、3。","碳氫氧化合物完全燃燒的配平有通式可用：CₓH_yO_z＋(x＋y\u002F4−z\u002F2)O₂→xCO₂＋(y\u002F2)H₂O。把乙醇的 x＝2、y＝6、z＝1 代入，氧氣係數為 2＋1.5−0.5＝3，與逐項平衡的結果一致。這條通式是速解各選項的利器：甲醇 x＝1、y＝4、z＝1 得 1.5 莫耳 O₂；乙醚 x＝4、y＝10、z＝1 得 4＋2.5−0.5＝6 莫耳 O₂；丙烯 x＝3、y＝6、z＝0 得 3＋1.5＝4.5 莫耳 O₂。可見題目選項中那些以分數呈現的係數，正是通式算出來的結果，並非印刷錯誤。\n\n配平之後可以再往兩個方向延伸。其一是理論空氣量：空氣中氧約占 21% 體積，故燃燒 1 莫耳乙醇所需理論空氣量約為 3÷0.21≈14.3 莫耳；換算質量比時，乙醇分子量 46、氧分子量 32，理論空氣質量比約為 (3×32÷0.232)÷46≈9.0，這類換算是熱釋放率與燃燒產物估算的基礎。其二是當量比的概念：實際供氧量與理論需氧量的比值決定燃燒是否完全，供氧不足時碳無法全部氧化為 CO₂，會大量生成一氧化碳與煤煙，這正是室內火災通風控制階段一氧化碳濃度飆高的化學原因。\n\n易混淆概念對照：醇類、醚類與烴類的分子式外觀相近，判別要點在有無氧原子與氧的接法——羥基(−OH)接在碳鏈末端者為醇，氧夾在兩個碳鏈之間者為醚，完全不含氧者為烴。命題者把甲醇、乙醚、丙烯與乙醇並列，測的就是這組結構辨識能力。乙醇本身是水溶性溶劑，這也連結到泡沫滅火的考點：一般泡沫遇乙醇會被脫水破泡，必須改用耐酒精型泡沫。\n\n延伸考點方向：燃燒熱與熱釋放率的計算(每莫耳乙醇完全燃燒的放熱量乘上質量燃燒速率)、燃燒範圍與閃火點的比較，以及水溶性醇類火災的滅火藥劑選用，都是由這條反應式往外長出來的題型。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-109-1-fire-science-032","已知天花板噴流溫度攝氏 135℃，天花板噴流速度 1.8 m\u002Fs，環境初始溫度 20℃，感知撒水頭作動溫度攝氏 72℃，反應時間指數 67(m1\u002F2s1\u002F2)，感知撒水頭作動時間為下列何者？（提示： ln115=4.74, ln63=4.14）",32,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-109-1-fire-science-034","BLEVE 的發生，下列敘述何者錯誤？",34,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-109-1-fire-science-031","建築物火災在閃燃發生後之全盛期火災的特性，不包括下列何者？",31,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-109-1-fire-science-035","有關引火性液體的敘述，下列何者正確？",35,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-109-1-fire-science-030","海龍替代滅火藥劑中，下列何者在大氣之滯留時間最久？",30,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-109-1-fire-science-036","房間的體積為 V=6 m×5 m×3 m，其中 O2 占 0.21 V，請問至少要加入多少公升（L）的 CO2 讓燃燒作用無法持續？",36,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-113-1-fire-science-033",113,"對於金屬鈉的敘述，下列何者錯誤？",{"webId":58,"year":59,"stem":60,"number":13},"fire-112-1-fire-science-033",112,"當防火門兩側的壓力差加倍時，其透過門縫所流出的氣體體積流率有何變化？",{"webId":62,"year":63,"stem":64,"number":13},"fire-111-1-fire-science-033",111,"執行危害性化學品災害搶救指導原則（HAZMAT），下列有關區域管制（Zoning）敘述何者錯誤？",{"webId":66,"year":67,"stem":68,"number":13},"fire-110-1-fire-science-033",110,"當一小爆炸發生時，其壓力波將全廠之粉塵揚起，再被隨後而至之燃燒引爆所引起之全廠性爆炸，此現象為何？",{"webId":70,"year":71,"stem":72,"number":13},"fire-108-1-fire-science-033",108,"電氣火災中，下列何者為積污導電現象？",1785129967395]