己知:HCN(aq)與NaOH(aq)反應(yīng)的△H=-12.1kJ/moL;HCl(aq)與NaOH(aq)反應(yīng)的△H=-55.6kJ/moL.則HCN在水溶液中電離的△H等于( ?。?br/>A. -67.7kJ/moL
B. -43.5kJ/moL
C. +43.5kJ/moL
D. +67.7kJ/moL
反應(yīng)的熱化學(xué)方程式分別為:
HCN(aq)+OH
-(aq)═CN
-(aq)+H
2O(l)△H=-12.1kJ?mol
-1…①
H
+(aq)+OH
-(aq)═H
2O(l)△H=-55.6kJ?mol
-1…②
用①-②可得HCN電離的熱化學(xué)方程式為:HCN(aq)
![](http://hiphotos.baidu.com/zhidao/pic/item/7c1ed21b0ef41bd585ac774252da81cb38db3d8c.jpg)
H
+(aq)+CN
-(aq)△H=-12.1kJ?mol
-1-(-55.6kJ?mol
-1)=+43.5kJ?mol
-1,
故選:C.