[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-108-1-fire-science-008":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-108-1-火災學概要-008","fire-108-1-fire-science-008",108,1,8,"若乙烷的燃燒熱為 350 kcal\u002Fmole，依據 Burgess-Wheeler 法則，下列何者最為接近乙烷的燃燒下限？",{"A":16,"B":17,"C":18,"D":19},"2.5%","3.0%","3.8%","4.5%","B",null,[],false,"本題考點：Burgess-Wheeler 法則——碳氫化合物的燃燒下限與莫耳燃燒熱之乘積近似為一定值（約 1,050 kcal\u002Fmole）。\n【正解理由】依 Burgess-Wheeler 法則，常溫常壓下烷類等碳氫化合物的燃燒下限 LFL（體積百分比）與其莫耳燃燒熱 ΔHc 的乘積約為定值，即 LFL × ΔHc ≒ 1,050 kcal\u002Fmole。題給乙烷燃燒熱 350 kcal\u002Fmole，代入得 LFL ≒ 1,050 ÷ 350 = 3.0%，四個選項中以 3.0% 最接近，故選 B。\n【逐項排除】\n(A) 2.5% 反推燃燒熱約 420 kcal\u002Fmole，與題給的 350 kcal\u002Fmole 不符；2.5% 較接近乙炔的實測燃燒下限。\n(B) 正確。1,050 ÷ 350 = 3.0，且乙烷實測燃燒下限約 3.0%，理論值與實測值相符，是本法則吻合度極佳的例子。\n(C) 3.8% 反推燃燒熱僅約 276 kcal\u002Fmole，係把定值誤記為 1,000 以下或運算時取錯位數，與乙烷的燃燒熱不合。\n(D) 4.5% 反推燃燒熱約 233 kcal\u002Fmole，已落在甲烷（約 210 kcal\u002Fmole、下限約 5%）的量級，屬碳數更少的分子。\n【記憶點】牢記定值 1,050：燃燒熱越大，燃燒下限越低，兩者相乘幾乎不變。","Burgess-Wheeler 法則是燃燒學少數可直接心算的經驗式，其背後想法是「火焰能否自我傳播，取決於單位體積混合氣燃燒後能否把前方未燃氣體加熱到著火溫度」。在下限濃度時，這個熱量剛好卡在臨界，因此不論分子種類為何，下限濃度乘上該分子的燃燒熱都會逼近同一個數字。以 kcal 表示約 1,050 kcal\u002Fmole，換算成 SI 單位約 4,400 kJ\u002Fmole，兩種數字都可能在題目中出現，要能互換。\n驗算幾個常見氣體即可看出準確度：甲烷燃燒熱約 210 kcal\u002Fmole，1,050 ÷ 210 = 5.0%，實測燃燒下限正是 5%；丙烷約 490 kcal\u002Fmole，得 2.14%，實測約 2.1%；丁烷約 635 kcal\u002Fmole，得 1.65%，實測約 1.8%。可見碳數越多、分子越大，燃燒熱越高、燃燒下限越低，這也是「重烴氣體外洩更危險」的量化解釋。但法則對氫氣、乙炔、一氧化碳等結構特殊的分子偏差較大，作答時應限用於烷類與一般碳氫化合物。\n與之配套的還有兩個公式。其一是溫度修正：LFL 隨溫度上升而下降，近似式為 LFL(T) = LFL(25℃) × [1 − (T − 25) ÷ 1,300]，說明火場高溫下原本濃度不足的氣體也可能落入可燃範圍。其二是混合氣體的勒沙特列公式：混合氣燃燒下限 L = 100 ÷ Σ（C_i ÷ L_i），C_i 為各成分佔可燃氣總量的百分比、L_i 為各成分的燃燒下限，是計算複合燃料危險性的標準工具。相關考點包括由燃燒熱推燃燒下限、由下限反推燃燒熱、以及燃燒範圍隨溫度與壓力變化的方向判斷。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-108-1-fire-science-007","下列有關蒸氣爆炸的敘述何者錯誤？",7,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-108-1-fire-science-009","就同一種可燃性粉塵而言，下列何種措施有助於降低發生粉塵爆炸的危險性？",9,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-108-1-fire-science-006","當受熱平面與熱輻射線方向垂直時，其輻射角為 0 度；兩者平行時，輻射角為 90 度。假設輻射源強度不變，當受熱平面由垂直逐漸傾斜，致使輻射角由 0 度增加至 60 度時，該平面所受的輻射熱通量變為原來的若干倍？",6,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-108-1-fire-science-010","安裝爆炸氣道（或洩爆孔、氣孔）可適度降低侷限空間中粉塵爆炸的危害，則下列敘述何者錯誤？",10,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-108-1-fire-science-005","可燃性液體的閃火點（flash point），是指當其表面蒸氣與空氣混合達燃燒下限時的：",5,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-108-1-fire-science-011","室內火災所產生的熱煙層由天花板向下沉降的時間直接影響逃生；以此觀點而論，下列何者較不利於逃生？",11,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-111-1-fire-science-008",111,"空氣氧之重量占整體之 23%，故 1 公斤碳完全燃燒需要多少空氣？",{"webId":58,"year":59,"stem":60,"number":13},"fire-110-1-fire-science-008",110,"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？",{"webId":62,"year":63,"stem":64,"number":13},"fire-109-1-fire-science-008",109,"1 度電為 1,000 瓦．小時（1 kWh），試問 1 度電約等同多少千卡（kcal）？",{"webId":66,"year":67,"stem":68,"number":13},"fire-107-1-fire-science-008",107,"描述熱傳遞（heat transfer）之物理量為下列何者？",{"webId":70,"year":71,"stem":72,"number":13},"fire-106-1-fire-science-008",106,"硫磺固體之燃燒屬於下列何種燃燒型態？",1785123163117]