①△U=Q+W
=nC-p△V
=1mol×9702cal·mol^-1－1atm×1677cm^3·g^-1×18.02g·mol^-1×1mol
=9702cal－1atm×1677cm^3×18.02
=9702×4.184J－1×101325Pa×1677×10^-6m^3×18.02
=37531J
=37.531kJ
②△V=0,W=0
△U=Q=nC=1mol×9702cal·mol^-1=9702×4.184J=40593J=40.593kJ
△H=△U+p△V=△U=40.593kJ