張來英 李海燕
摘要:本文介紹了如何用微量量熱法研究蔗糖水解反應(yīng)的熱動力學,通過實驗和計算得出了該反應(yīng)的速率常數(shù)。
關(guān)鍵詞:蔗糖水解;量熱法;熱動力學
中圖分類號:O6;G64 文獻標志碼:A 文章編號:1674-9324(2016)19-0165-03
四、結(jié)果與討論
實驗結(jié)果如表2。
量熱法[1-3]適用范圍寬,處理方便,具有不受體系光譜性質(zhì)(如旋光法)、電學性質(zhì)(如電導法)限制的獨特性質(zhì)。采用本方法,可利用圖解求反應(yīng)速率常數(shù)及相關(guān)熱動力學參量,結(jié)果準確度較高。將此方法用于處理諸如聚合反應(yīng)、膠束催化等,用常規(guī)動力學方法較難以處理的反應(yīng)體系有很大的優(yōu)越性。
對一些未知反應(yīng)級數(shù)的不可逆反應(yīng),可采用變更初始濃度,并從相應(yīng)的熱譜上確定Q■/Q■=1/2的時間(半衰期t1/2),最后利用lgt■=lgK+(1-n)lgC■,由作圖法確定反應(yīng)級數(shù)n。對一些整數(shù)級數(shù)的反應(yīng),也可將熱譜數(shù)據(jù)分別代入表1中各已知級數(shù)的熱動力學方程,當?shù)玫降那€為直線時,該反應(yīng)的級數(shù)便是對應(yīng)方程的級數(shù)。
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