[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-110-1-fire-science-007":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-110-1-火災學概要-007","fire-110-1-fire-science-007",110,1,7,"己烷在閃火點時的飽和蒸氣壓為 9.12 mmHg，根據 Burgess-Wheeler 定理其燃燒熱約為多少 kcal\u002Fmole？",{"A":16,"B":17,"C":18,"D":19},"682","782","882","982","C",null,[],false,"本題考點：閃火點(液面蒸氣濃度恰達燃燒下限)結合 Burgess-Wheeler 定理反推燃燒熱。\n【正解理由】閃火點是液面蒸氣與空氣之混合氣恰達燃燒下限之最低溫度,故可由該溫度之飽和蒸氣壓依道爾頓分壓定律求得燃燒下限;再依 Burgess-Wheeler 定理,燃燒下限(體積%)與燃燒熱(kcal\u002Fmole)之乘積約為定值 1059,代入得約 882 kcal\u002Fmole,故選 C。\n【逐項排除】\n(A) 682 kcal\u002Fmole 對應之燃燒下限約 1.55%,與題給蒸氣壓換算所得之 1.2% 不合。\n(B) 782 kcal\u002Fmole 對應之燃燒下限約 1.35%,同樣偏離題給蒸氣壓對應之濃度。\n(C) 882 kcal\u002Fmole 由 1059 ÷ 1.2 求得,與己烷燃燒熱之數量級相符,為本題應選者。\n(D) 982 kcal\u002Fmole 對應之燃燒下限約 1.08%,須蒸氣壓約 8.2 mmHg 才會出現,與題給值不合。\n【演算步驟】燃燒下限 LFL = (9.12 mmHg ÷ 760 mmHg) × 100% = 1.2 vol%;Burgess-Wheeler 定理 LFL × ΔHc ≈ 1059 kcal\u002Fmole;ΔHc = 1059 ÷ 1.2 ≈ 882.5 kcal\u002Fmole,取 882。\n【記憶點】蒸氣壓除以 760 得下限,1059 除以下限即得燃燒熱。","Burgess-Wheeler 定理的內涵是:各種碳氫化合物在其燃燒下限濃度時,完全燃燒所釋出的熱量大致相同,約為每莫耳 1059 kcal(亦有取 1050 kcal,以國際單位表示約 4.35 MJ\u002Fmole)。其物理意義在於,燃燒下限對應的是「剛好能維持火焰自行傳播」的最低放熱量,約可使混合氣升溫至攝氏一千度上下的臨界火焰溫度;燃料分子的燃燒熱愈大,只需愈低的濃度即可跨過此門檻,故燃燒下限與燃燒熱成反比。\n閃火點與燃燒下限之間的橋樑則是道爾頓分壓定律:在一大氣壓(760 mmHg)下,蒸氣的體積分率等於其分壓除以總壓,故 9.12 mmHg 即對應 1.2 vol%。這條換算是消防化學的通用工具——已知閃火點時之蒸氣壓可求燃燒下限,反之已知燃燒下限亦可回推閃火點時的蒸氣壓,兩個方向都會考。\n單位與數量級須留意:燃燒熱以 kcal\u002Fmole 表示時,己烷落在八百多的量級;若題目改以 kJ\u002Fmole 給值,須先以 1 kcal ≈ 4.184 kJ 換算,882 kcal\u002Fmole 約等於 3690 kJ\u002Fmole。另一個常見陷阱是把體積分率誤寫成小數 0.012 代入,答案會膨脹一百倍,務必確認 Burgess-Wheeler 定理中的燃燒下限是以百分比數值代入。\n易混淆對照:閃火點是有外部火源時「閃燃一下即熄」的最低溫度;著火點(燃點)通常較閃火點高數度,點燃後可持續燃燒;自燃點則不需外部火源。三者與燃燒下限的關係,以及與勒沙特列定律(混合氣體燃燒界限)的併用,構成同一條公式串起的考點群。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-110-1-fire-science-006","阿里山發生森林火災，已知火災當天的相對濕度為 60.0%，前一天相對濕度為 50.0%，再前一天相對濕度為 40.0%，試求火災當天的實效濕度？",6,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-110-1-fire-science-008","根據美國防火協會危險物品標示規定，將危險類別記載於菱形方塊上，其中「有害健康毒性」以何種顏色表示？",8,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-110-1-fire-science-005","已知乙烷、乙烯、乙炔的發火能量分別為 a、b、c，則 a、b、c 的大小關係為：",5,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-110-1-fire-science-009","碳化鈣（CaC2，俗稱電石）常用於水果的催熟，屬於公共危險物品，遇水會起激烈反應產生下列何種可燃性氣體？",9,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-110-1-fire-science-004","在氣溫 20 ℃無風的情況下，一般木造建築物形成危險界限溫度之輻射熱通量超過多少 kcal \u002F m2 h 即有延燒之危險？",4,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-110-1-fire-science-010","甲基乙基酮過氧化物（MEKPO）常用於聚合物的生產，加熱至 100 ℃時會發生爆炸，此化合物屬於那一類公共危險物品？",10,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-111-1-fire-science-007",111,"油類火災為何種火災？",{"webId":58,"year":59,"stem":60,"number":13},"fire-109-1-fire-science-007",109,"進入石化工廠，車輛會被要求在排氣管加裝滅焰器（flame arrester）以避免火災爆炸之發生，加裝該措施防制火災爆炸之原理為：",{"webId":62,"year":63,"stem":64,"number":13},"fire-108-1-fire-science-007",108,"下列有關蒸氣爆炸的敘述何者錯誤？",{"webId":66,"year":67,"stem":68,"number":13},"fire-107-1-fire-science-007",107,"可燃物於無明火等火源之條件下，在大氣中僅因受熱而開始自行燃燒所需之最低溫度稱為下列何者？",{"webId":70,"year":71,"stem":72,"number":13},"fire-106-1-fire-science-007",106,"請指出下列何種氣體的比重小於 1？",1785123162284]