已知:① CO2(g)+4H2(g) = CH4(g)+2H2O(l) △H1 = -252.9 kJ/mol
②2H2O(l) = 2H2(g)+O2(g) △H2 = +571.6 kJ/mol
③ H2O(l) = H2O(g) △H3 = +44.0 kJ/mol
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