[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-109-1-fire-science-017":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-017","fire-109-1-fire-science-017",109,1,17,"T.N.T.炸藥化學名稱為三硝基甲苯（Trinitrotolene，C7H5N3O6），俗稱黃色炸藥，試問其氧平衡（Oxygen Balance, O.B.）為多少？",{"A":16,"B":17,"C":18,"D":19},"-64.0%","-74.0%","-84.0%","-94.0%","B",null,[],false,"本題考點：氧平衡（Oxygen Balance）的定義式與計算，用以判斷含能物質自身氧量的盈缺。\n【正解理由】對 CaHbNcOd 型化合物，氧平衡 O.B.％＝−1600×(2a＋b\u002F2−d)\u002FM，括號內是把碳全部氧化成 CO₂、氫全部氧化成 H₂O 所需的氧原子數扣掉自帶氧原子數，係數 1600 來自氧原子量 16 乘以百分比換算的 100，M 為分子量。三硝基甲苯 C7H5N3O6 的 M＝7×12＋5×1＋3×14＋6×16＝227，括號值＝2×7＋5÷2−6＝10.5，故 O.B.＝−1600×10.5÷227＝−16800÷227≒−74.0％，負值代表自身含氧不足以完全氧化，故選 B。\n【逐項排除】\n(A) −64.0％：在括號值 10.5 不變的前提下須分子量約 263 才成立，與 TNT 的 227 不符。\n(B) −74.0％：由 −1600×10.5÷227 直接得出，與 C7H5N3O6 的原子組成完全相符，為本題應選者。\n(C) −84.0％：對應分子量約 200，相當於漏算一個氮原子加一個碳的質量。\n(D) −94.0％：對應括號值約 13.3，相當於氫項忘了除以 2 且高估碳數，偏離最遠。\n【記憶點】O.B.＝−1600×(2C＋H÷2−O)÷分子量；TNT 記 −74％，負得越多代表越依賴外界供氧。","氧平衡衡量的是「含能分子自帶的氧夠不夠把自己燒完」。定義式中的括號項，是把碳全部氧化成二氧化碳（每個碳需 2 個氧）、氫全部氧化成水（每 2 個氫需 1 個氧）所需的氧原子總數，再扣掉分子自帶的氧原子數；乘以氧原子量並換算成百分比，即得每 100 公克物質缺（或多）幾公克氧。負值代表缺氧，正值代表餘氧。氮通常以 N₂ 形式逸出、不計入需氧量，這是計算時最常被誤加的一項。\n\n幾組必背對照：三硝基甲苯 C7H5N3O6 為 −74％，屬明顯負氧平衡；硝化甘油 C3H5N3O9 的括號值為 6＋2.5−9＝−0.5、分子量同為 227，O.B.＝＋3.5％，接近零而略帶正值；硝酸銨 NH4NO3 分子量 80，括號值 0＋2−3＝−1，O.B.＝＋20％，是典型的富氧氧化劑。\n\n這組數字解釋兩件現象。其一，爆炸威力在氧平衡接近零時最大，所以強負氧平衡的 TNT 常與強正氧平衡的硝酸銨混合成阿馬托（Amatol）炸藥，硝酸銨也常配燃料油成為 ANFO，靠互補把整體氧平衡拉回零附近。其二，負氧平衡物質爆炸後會產生大量一氧化碳、游離碳與未燃碳氫，因而伴隨濃黑煙、二次燃燒與中毒危害；正氧平衡物質則傾向生成氮氧化物。\n\n同一考點的其他問法：給分子式直接求 O.B.、比較兩種物質何者威力較大、或由氧平衡推斷爆炸後的煙色與有毒氣體種類。失分點集中在三處——氫項忘記除以 2、把氮算進需氧量、以及分子量加錯，其中分子量是最容易在考場上算錯的一步，建議先寫成 84＋5＋42＋96 再相加。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-109-1-fire-science-016","假設建築物外部風速為 10 m\u002Fs，風壓係數為 0.6，空氣密度為 1.0 kg\u002Fm3，其對迎風面建築物所產生的風壓約為？",16,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-109-1-fire-science-018","化學災害搶救程序 HAZMAT 之說明，下列何者正確？",18,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-109-1-fire-science-015","下列海龍替代滅火藥劑，何者之化學組成為五氟乙烷？",15,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-109-1-fire-science-019","若一物體的溫度為 327℃，輻射率（ Emissivity）為 0.1，已知史蒂芬–波茲曼常數為 5.67×10-8 W\u002Fm2k4，則其輻射強度（Emissive Power）約為多少？",19,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-109-1-fire-science-014","火場溫度隨燃燒時間而逐漸升高，其空氣亦漸膨脹，空氣由外界流入該起火房間，同時熱煙霧也會從該起火房間流出。若忽略燃燒分解過程而產生之質量流率，建築物內部空氣溫度為 25℃，起火房間溫度為 800℃，流入起火房間之空氣體積流量為 1 m3\u002Fs，則流出起火房間之熱煙霧體積流量約為若干？",14,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-109-1-fire-science-020","某研究院之廠區引發爆燃事件之推進劑，其內含過氯酸鹽類，試問其為公共危險物品中第幾類物質？",20,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-111-1-fire-science-017",111,"有關閃燃（Flashover）與複燃（Backdraft）的敘述，何者錯誤？",{"webId":58,"year":59,"stem":60,"number":13},"fire-110-1-fire-science-017",110,"下列惰性氣體類海龍替代滅火藥劑中，何者的比重小於 1？",{"webId":62,"year":63,"stem":64,"number":13},"fire-108-1-fire-science-017",108,"危害物質可能因混合儲存或載運而衍生危險，則下列那兩類公共危險物品於混合載運時的危險性最低？",{"webId":66,"year":67,"stem":68,"number":13},"fire-107-1-fire-science-017",107,"有關地下建築物火災之敘述，下列何者錯誤？",{"webId":70,"year":71,"stem":72,"number":13},"fire-106-1-fire-science-017",106,"根據火場能見度（S）與消光係數（K）間之經驗公式，對於發光物體之敘述何者正確？",1785123162792]