[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-110-1-fire-science-015":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-015","fire-110-1-fire-science-015",110,1,15,"下列有關液化天然氣（LNG）與液化石油氣（LPG）之比較，何者正確？",{"A":16,"B":17,"C":18,"D":19},"液化天然氣燃燒產生的燃燒熱小於液化石油氣","液化天然氣燃燒所需的理論空氣量大於液化石油氣","液化天然氣的燃燒下限小於液化石油氣","液化天然氣的比重較空氣重，液化石油氣的比重較空氣輕","A",null,[],false,"本題考點：液化天然氣（LNG，主成分甲烷）與液化石油氣（LPG，主成分丙烷、丁烷）在燃燒熱、理論空氣量、燃燒下限與比重上的差異。\n【正解理由】氣體燃料的發熱量以每莫耳或標準狀態下每立方公尺為比較基準。甲烷完全燃燒放熱約 890 kJ\u002Fmol，丙烷約 2,220 kJ\u002Fmol、丁烷約 2,880 kJ\u002Fmol，碳數愈多放熱愈大，故 LNG 的燃燒熱小於 LPG，故選 A。\n【逐項排除】\n(A) 以相同體積或莫耳數比較，甲烷放熱明顯低於丙烷與丁烷，敘述正確。\n(B) 錯在方向相反：甲烷完全燃燒需 2 莫耳氧，丙烷需 5 莫耳、丁烷需 6.5 莫耳，LNG 所需理論空氣量小於 LPG。\n(C) 錯在方向相反：甲烷燃燒下限約 5 vol%，丙烷約 2.1 vol%、丁烷約 1.8 vol%，LNG 的燃燒下限大於 LPG。\n(D) 兩者比重敘述顛倒：甲烷分子量 16，蒸氣對空氣比重約 0.55 比空氣輕；丙烷、丁烷分子量 44 與 58，比重約 1.5 至 2.0 比空氣重。\n【記憶點】天然氣輕而難燃、放熱少；石油氣重而易燃、放熱多。","兩種燃氣的差異全部源自碳數。LNG 以甲烷為主（約 85 至 95 %），常壓下須冷卻至約 −162 ℃ 才液化，屬低溫液化；LPG 以丙烷與丁烷為主，常溫下加壓數個大氣壓即可液化，屬加壓液化。這兩種液化方式的不同，也決定了外洩型態：LNG 洩漏後初期為低溫冷氣體會短暫下沉，回溫後迅速上浮擴散；LPG 洩漏後始終比空氣重，沿地面流動並滯留於低窪處、地下室與管溝，形成範圍更大的可燃氣雲。\n關鍵數據宜成組記憶。甲烷：分子量 16，對空氣比重 0.55，燃燒範圍約 5 至 15 vol%，每莫耳需氧 2 莫耳、需空氣約 9.5 莫耳，燃燒熱約 890 kJ\u002Fmol。丙烷：分子量 44，比重約 1.55，燃燒範圍約 2.1 至 9.5 vol%，每莫耳需氧 5 莫耳、需空氣約 23.8 莫耳，燃燒熱約 2,220 kJ\u002Fmol。丁烷：分子量 58，比重約 2.0，燃燒範圍約 1.8 至 8.4 vol%，燃燒熱約 2,880 kJ\u002Fmol。由此可歸納通則：碳數愈多，分子量與比重愈大、燃燒範圍下限愈低、理論空氣量與燃燒熱愈大。\n須留意比較基準。以單位質量計算時，甲烷因氫碳比最高而發熱量表現不同於體積基準，本科題目在比較兩種燃氣時慣以體積或莫耳為基準，讀題時先確認基準再作答，可避免落入陷阱選項。\n這組差異也直接影響火災危險的判斷：LPG 因燃燒下限低、比重大而更容易累積至可燃濃度並發生氣雲爆炸；LNG 則易向上擴散，其危害多在密閉空間頂部聚積與低溫凍傷。瓦斯漏氣檢知器的裝置高度規定即循此差異設計，較空氣輕者設於天花板附近、較空氣重者設於接近地面處，是與設備科交叉出題的常見接點。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-110-1-fire-science-014","自然發火性物質中的原棉，主要是因為下列何種熱之蓄積而發火？",14,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-110-1-fire-science-016","市面上販售的 ABC 乾粉滅火器內充填的乾粉滅火藥劑主要成分為：",16,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-110-1-fire-science-013","有一開口面積為 10.0 m2，開口高度為 1.44 m 之居室，當其發生火災而形成通風控制燃燒時，根據 P. H. Thomas 之研究結果，則燃燒速度為多少 kg\u002Fmin？",13,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-110-1-fire-science-017","下列惰性氣體類海龍替代滅火藥劑中，何者的比重小於 1？",17,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-110-1-fire-science-012","根據 NFPA265 對閃燃現象（flashover）之定義，下列敘述何者錯誤？",12,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-110-1-fire-science-018","根據「危害物質災害現場搶救標準作業程序」之規定，其首要工作為何？",18,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-111-1-fire-science-015",111,"下列發火源在理化現象歸類上，何者與其他不同類別？",{"webId":58,"year":59,"stem":60,"number":13},"fire-109-1-fire-science-015",109,"下列海龍替代滅火藥劑，何者之化學組成為五氟乙烷？",{"webId":62,"year":63,"stem":64,"number":13},"fire-108-1-fire-science-015",108,"下列何種現象對於局部電阻所產生的效應恰與其他三者相反？",{"webId":66,"year":67,"stem":68,"number":13},"fire-107-1-fire-science-015",107,"有一火場之消光係數為 2 m-1，請問發光物體之能見度為多少公尺？",{"webId":70,"year":71,"stem":72,"number":13},"fire-106-1-fire-science-015",106,"粉塵爆炸與可燃性氣體相同，亦須存在有「最小發火能量」始可能引起粉塵爆炸，下列有關粉塵爆炸「最小發火能量」之敘述何者錯誤？",1785123162375]