题目
计算: (1) 1.3-(-2.7); (2) (-13)-(-17); (3) (-1.8)-(+4.5); (4) 6.38-(-2.62); (5) ; (6) . 答案:解:1.3-(-2.7)=1.3+2.7=4
解:(-13)-(-17)=(-13)+(+17)=4
解:(-1.8)-(+4.5)=(-1.8)+(-4.5)=-6.3;
解:6.38-(-2.62)=6.38+2.62=9
解: (−14)−(−13) = −14+13=112
解: (−6.25)−(−314) = −614+314=−3已知:Fe2O3(s)+3C(石墨)=2Fe(s)+3CO(g)ΔH=+489.0 kJ·mol-1①CO(g)+O2(g)=CO2(g)ΔH=-283.0 kJ·mol-1②C(石墨)+O2(g)=CO2(g)ΔH=-393.5 kJ·mol-1③则4Fe(s)+3O2(g)=2Fe2O3(s)的ΔH为( )A.+1 164.1 kJ·mol-1 B.-1 641.0 kJ·mol-1C.-259.7 kJ·mol-1D.-519.4 kJ·mol-1