问题 问答题

(1)请用热化学方程式表示:

A.1mol N2(g)与适量H2(g)起反应,生成2mol NH3(g),放出92.2kJ热量______.

B.1mol N2(g)与适量O2(g)起反应,生成2mol NO2(g),吸收68kJ热量______.

(2)随着科学技术的进步,人们研制出了多种类型的甲醇质子交换膜燃料电池,以满足不同的需求.有一类甲醇质子交换膜燃料电池,需将甲醇蒸气转化为氢气,两种反应原理是

A、CH3OH(g)+H2O(g)=CO2(g)+3H2(g)△H=+49.0kJ/mol

B、CH3OH(g)+3/2O2(g)=CO2(g)+2H2O(g)△H=-192.9kJ/mol

由上述方程式可知,CH3OH的燃烧热______(填“大于”、“等于”或“小于”)192.9kJ/mol.已知水的气化热为44kJ/mol,则氢气燃烧热的热化学方程式为______.

答案

(1)A.1mol N2(g)与适量H2(g)起反应,生成2mol NH3(g),放出92.2kJ热量的热化学方程式为:N2(g)+3H2(g)⇌2NH3(g)△H=-92.2kJ/mol,故答案为:N2(g)+3H2(g)⇌2NH3(g)△H=-92.2kJ/mol;

B.1mol N2(g)与适量O2(g)起反应,生成2mol NO2(g),吸收68kJ热量的热化学方程式为N2(g)+2O2(g)=2NO2(g)△H=+68kJ/mol,故答案为:N2(g)+2O2(g)=2NO2(g)△H=+68kJ/mol;

(2)因燃烧热在某一温度和压强下lmol某物质B完全燃烧生成稳定化合物时所释放出的热量,而H2O的稳定化合物是液态水,H2O蒸汽转变为液态水需要放热,所以CH3OH的燃烧热大于192.9kJ/mol;

     CH3OH(g)+H2O(g)=CO2(g)+3H2(g)△H=+49.0kJ/mol      ①

    CH3OH(g)+3/2O2(g)=CO2(g)+2H2O(g)△H=-192.9kJ/mol   ②

 ②-①得  3H2(g)+3/2O2(g)=3H2O(g)△H=-241.9kJ/mol   ③

                      H2O(l)=H2O(g)△H=+44kJ/mol    ④

③-④×3 得 3H2(g)+3/2O2(g)=3H2O(g)△H=-373.9kJ/mol 即H2(g)+1/2O2(g)=H2O(l)△H=-124.6kJ/mol,

故答案为:大于;H2(g)+1/2O2(g)=H2O(l)△H=-124.6kJ/mol.

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