[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-112-1-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-112-1-火災學概要-007","fire-112-1-fire-science-007",112,1,7,"高壓氣體之爆炸界限，通常較常壓下為廣，下列何者氣體之爆炸界限，會呈現加壓時上、下限初呈狹窄，但繼續加壓後又變廣的現象？",{"A":16,"B":17,"C":18,"D":19},"H2","CH4","C2H4","CO","A",null,[],false,"本題考點：壓力對爆炸界限的影響，以及氫氣在加壓過程中界限先收窄、繼續加壓後又擴大的特殊行為。\n【正解理由】依燃燒學原理，可燃氣體加壓後單位體積分子數增加、碰撞頻率上升，火焰帶熱量不易散失，爆炸上限因而上移、界限範圍變廣，這是一般氣體的常態。氫氣則是教科書列舉的例外：自常壓往上加壓的初期區間，上限先下降、下限略微上升，界限反而收窄；壓力繼續升高後上限再度上移，界限又變廣，整體呈先窄後廣的變化。題幹描述的正是此現象，故選 A。\n【逐項排除】\n(A) H2 氫：加壓初期界限收窄、繼續加壓又擴大，與題幹敘述相符，為本題應選者。\n(B) CH4 甲烷：加壓後上限單調上移（常壓約 5%～15%,高壓下上限可達 40% 以上）,沒有先收窄的階段。\n(C) C2H4 乙烯：常壓約 2.7%～36%,加壓後亦屬界限單調擴大者，不呈先窄後廣。\n(D) CO 一氧化碳：是加壓後爆炸界限反而收窄的典型氣體，且不會回頭變廣，與題幹描述的兩階段變化不同。\n【記憶點】加壓後界限擴大是常態；氫氣先窄後廣、一氧化碳單向收窄，兩個例外分開記。","壓力對爆炸界限的影響，來自碰撞頻率與熱損失的競爭。加壓使單位體積內分子數增加，自由基與燃料分子碰撞機率上升、火焰帶的熱量相對不易散失，原本因氧氣相對不足而無法傳播火焰的濃度也能燃燒，所以上限明顯上移、界限範圍擴大；減壓則相反，壓力降到某一臨界值以下時，上下限會收斂到同一點而完全不燃，這也是高空與真空環境防火分析的理論基礎。\n氫氣的例外行為屬必背考點：自常壓加壓的初期（約十餘至二十大氣壓的區間）,上限先下降、下限略升，界限收窄；壓力繼續升高後上限再度上移，界限又擴大。一般以反應機構解釋：該壓力區間內三體反應（H·＋O2＋M→HO2·＋M）的比重相對於鏈分支反應（H·＋O2→OH·＋O·）上升，而 HO2· 是活性較低的自由基，使鏈分支效率暫時下降；壓力更高時，整體反應速率的提升又壓過此效應。\n一氧化碳則是另一個方向的例外：加壓後爆炸界限反而收窄，且不像氫氣會回頭擴大。此外一氧化碳的界限對水分含量極為敏感，在完全乾燥狀態下幾乎難以點燃，含微量水蒸氣才能順利傳播火焰，因為其氧化主要靠 OH· 自由基推動。\n整組記憶方式是：常態加壓擴大、氫先窄後廣、一氧化碳單向收窄。相關考點還包括：溫度上升使界限擴大；惰性氣體摻入使上限下移並導向最小氧濃度（MOC）;以危險度 H＝（上限−下限）÷下限 比較氣體危險性；以及高壓氣體洩漏時，因焦耳-湯姆生效應與噴流靜電所生的引燃風險，常與氫的最小引燃能量僅約 0.02 mJ 合併命題。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-112-1-fire-science-006","在標準狀態下，下列氣體中何者之爆炸範圍最廣？",6,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-112-1-fire-science-008","赤磷和黃磷分屬我國法定公共危險物品那一類？",8,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-112-1-fire-science-005","鄰二甲苯的閃火點為 157℃，若鄰二甲苯於 157℃時的飽和蒸氣壓為 2.0 mmHg，試求其燃燒下限為何？",5,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-112-1-fire-science-009","下列何者屬於我國法定公共危險物品中的易燃固體？",9,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-112-1-fire-science-004","若空氣中的氧氣體積百分比為 21%，則甲烷完全燃燒的化學理論濃度為多少%？",4,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-112-1-fire-science-010","依據 NFPA（美國防火協會）危險性物品標示，有關「反應性」的敘述，下列何者正確？",10,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-114-1-fire-science-007",114,"油類火災沸溢（Boilover）與濺溢（Spilover）現象之發生區別，下列何者錯誤？",{"webId":58,"year":59,"stem":60,"number":13},"fire-113-1-fire-science-007",113,"依公共危險物品及可燃性高壓氣體製造儲存處理場所設置標準暨安全管理辦法，第四類公共危險物品對於易燃液體定義，是指在一大氣壓時，閃火點在攝氏幾度以下之液體？",{"webId":62,"year":63,"stem":64,"number":13},"fire-111-1-fire-science-007",111,"油類火災為何種火災？",{"webId":66,"year":67,"stem":68,"number":13},"fire-110-1-fire-science-007",110,"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？",{"webId":70,"year":71,"stem":72,"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：",1785129966450]