问题 选择题
已知298K时下述反应:

①C(s)+1/2O2(g)=CO(g)△H1=-110.5kJ•mol-1

②CO(g)+1/2O2(g)=CO2(g)△H2=-283.0kJ•mol-1

③C(s)+CO2(g)=2CO(g)△H3

则△H3等于(   )

A.172.5kJ•mol-1

B.-172.5kJ•mol-1

C.393.5kJ•mol-1

D.-393.5kJ•mol-1

答案

答案:A

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