Question

【题目】已知①H2(g)+1/2O2(g)=H2O(l) △H =-284.2kJ /mo1

②2NH3(g)+3/2O2(g)=N2(g)+3 H2O(l) △H =-760.2 kJ /mo1

则可推知1/2 N2(g)+ 3/2H2(g)= NH3(g) 的△H是

A. -91.96 kJ/mol B. -104.5 kJ/mol

C. +476.52 kJ/mol D. -46.2 kJ/mol

Answer 1

【答案】D

【解析】试题分析：已知 ①H2(g)+1/2O2(g)=H2O(l) △H ="-284.2kJ" /mo1；

②2NH3(g)+3/2O2(g)=N2(g)+3 H2O(l) △H ="-760.2" kJ /mo1。

根据盖斯定律：①×3/2-②×1/2得1/2 N2(g)+ 3/2H2(g)= NH3(g) 的△H="-46.2" kJ/mol，选D。