问题 选择题

下列推论正确的是:

A.S(g)+O2(g)==SO2(g)△H1;S(s)+O2(g)==SO2(g) △H2,则:△H1>△H2

B.C(石墨,s)=C(金刚石,S)△H="+1.9" kJ/mol,则由石墨制取金刚石的反应是吸热反应,金刚石比石墨稳定

C.NaOH(aq)+HCl(aq)=NaCl(aq)+H2O(I)△H=﹣57.4 kJ/mol,则:含20 gNaOH的稀溶液与稀盐酸完全反应,放出的热量为28.7 kJ

D.2C(s)+O2(g)=2CO(g)△H=﹣221 kJ/mol,则碳的燃烧热等于110.5kJ/mol

答案

答案:C

题目分析:A.由于同种物质在气态时含有的能量比固态时高,所以前者放出的热量比后者高,因此△H1 <△H2。错误。B.由于石墨转化为金刚石时吸收热量,说明由石墨制取金刚石的反应是吸热反应,物质所含有的能量越低该物质的稳定性就越强。因此金刚石不如石墨稳定。错误。C.NaOH(aq)+ HCl (aq)=NaCl(aq)+H2O(I)△H=﹣57.4 kJ/mol,说明每有1mol的NaOH发生酸碱中和反应会放出热量57.4 kJ则:含20 gNaOH的稀溶液即NaOH的物质的量为0.5mol与稀盐酸完全反应,放出的热量为28.7 kJ.正确。D.1mol的物质完全燃烧产生稳定的氧化物时放出的热量叫该物质的燃烧热。C的稳定的氧化物是气态的CO2,因此碳的燃烧热大于110.5kJ/mol。错误。

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