[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-110-1-fire-science-024":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-024","fire-110-1-fire-science-024",110,1,24,"在充足的能量下，下列何種濃度（vol%）的氫氣（H2）為燃燒界限範圍內？",{"A":16,"B":17,"C":18,"D":19},"100%","80%","50%","2%","C",null,[],false,"本題考點：氫氣在空氣中的燃燒(爆炸)界限,下限約 4 vol%、上限約 75 vol%。\n【正解理由】可燃氣體必須與空氣形成適當比例的混合氣,濃度落在燃燒下限與燃燒上限之間,火焰才能自行傳播;低於下限因燃料太稀、釋熱量不足以加熱鄰近未燃混合氣,高於上限則因氧化劑不足,兩者皆無法持續燃燒。氫氣的燃燒界限約為 4～75 vol%,是常見可燃氣體中範圍最寬者之一。50 vol% 正落在此區間內,故選 C。\n【逐項排除】\n(A) 100%:代表純氫環境、完全沒有氧化劑存在,遠高於上限 75%,即使能量充足亦無從氧化,不可能燃燒。\n(B) 80%:高於上限 75%,空氣比例過低而氧氣不足,屬過濃無法傳播火焰的範圍。\n(C) 50%:介於 4% 與 75% 之間,位於燃燒界限範圍內,正確。\n(D) 2%:低於下限 4%,燃料過稀,釋熱不足以維持火焰傳播。\n【記憶點】氫氣「四到七五」範圍最寬;太稀點不著、太濃沒有氧。","燃燒界限並非固定不變的物性,而是隨條件變動的實驗值。溫度升高時,分子動能增加、反應更易維持,下限會下移、上限會上移,範圍變寬;壓力升高對上限影響尤其明顯(下限相對穩定);加入氮氣、二氧化碳等惰性氣體則使氧濃度下降,上限先急速壓縮,最終上下限收斂於一點,該點對應的氧濃度即為最小氧濃度,是惰化與窒息式滅火的理論依據。\n\n常考的界限數值宜整批背:甲烷 5～15、乙烷 3～12.4、丙烷 2.1～9.5、丁烷 1.8～8.4、一氧化碳 12.5～74、氨 15～28、乙炔 2.5～100(上限達 100 是因其可自行分解放熱)。可用危險度 H =(上限 − 下限)÷ 下限 量化風險:氫氣為(75 − 4)÷ 4 ≈ 17.8,乙炔高達 39,甲烷僅 2,數字越大代表越容易落入可燃範圍。\n\n混合氣體的下限則用勒沙特列公式:100 ÷ L =(V₁ ÷ L₁)+(V₂ ÷ L₂)+ …,其中 V 為各成分體積百分比、L 為各自的下限。這條式子與本題屬同一考點群,常搭配「某混合氣是否已達可燃範圍」的判斷題出現。另需留意題目問的是體積百分比而非質量百分比,兩者不可混用——燃燒界限一律以體積(莫耳)濃度定義。\n\n溫度的量化影響可用柏格斯–惠勒法則概估:溫度每升高 100 ℃,下限約下降原值的 8%、上限約上升 8%,用以評估高溫環境中原本安全的濃度是否已進入可燃範圍。壓力方面則不對稱,下限受影響甚小,上限隨壓力升高而顯著擴大,因此高壓儲氣設備的風險評估不能直接套用常壓數據。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-110-1-fire-science-023","請問 2 公斤的氫氣（H2）完全燃燒，所需要的理論空氣量為多少公斤？",23,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-110-1-fire-science-025","請依據可燃性氣體完全燃燒時的化學理論濃度，計算丙烷的燃燒下限？",25,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-110-1-fire-science-022","火災中所產生的輻射熱量與下列何者成正比？",22,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-110-1-fire-science-026","易燃性氣體受到壓縮後溫度會有升高的狀況發生，可能會發火導致火災的發生，此現象為何？",26,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-110-1-fire-science-021","下列物質在常溫時，何者的熱傳導係數（W\u002Fm∙K）較低？",21,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-110-1-fire-science-027","某建築物的插座電壓為 110 伏特，在其延長線上的插座同時插 880 瓦的電磁爐、110 瓦的電風扇及 1100 瓦的電熱器，請問該延長線之額定電流至少需多少安培？",27,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-111-1-fire-science-024",111,"下列何者非影響建築物中煙霧流動與蔓延的主要因素？",{"webId":58,"year":59,"stem":60,"number":13},"fire-109-1-fire-science-024",109,"在古蹟及歷史建築物火災風險評估指標中，有關防火因應措施安全評估項目中，不包括下列何項？",{"webId":62,"year":63,"stem":64,"number":13},"fire-108-1-fire-science-024",108,"下列有關燃燒上下限之敘述，何者錯誤？",{"webId":66,"year":67,"stem":68,"number":13},"fire-107-1-fire-science-024",107,"容易著火之燃料具下列何種特性？",{"webId":70,"year":71,"stem":72,"number":13},"fire-106-1-fire-science-024",106,"假設正向煙囪效應在中性帶以上 8 m 處的壓差為 10 Pa，若建築物內、外的溫差不變，中性帶以上 20 m 處的壓差為多少？",1785123162462]