2NO_(2)(g)to N_(2)O_(4)(g) DeltaU_(f)^(@)[N_(2)O_(4)(g)]=2kcal//"moleand "DeltaU_(reaction)^(@)=-16kcal//mol, then calculate DeltaH_("formation" )^(@)=-16kcal//mol,then calculate DeltaH_("formation")^(@) of NO_(2)at 727^(@)C:

2NO_(2)(g)to N_(2)O_(4)(g) DeltaU_(f)^(@)[N_(2)O_(4)(g)]=2kcal//"molea

1.	2NO_(2)(g)to N_(2)O_(4)(g) DeltaU_(f)^(@)[N_(2)O_(4)(g)]=2kcal//"moleand "DeltaU_(reaction)^(@)=-16kcal//mol, then calculate DeltaH_("formation" )^(@)=-16kcal//mol,then calculate DeltaH_("formation")^(@) of NO_(2)at 727^(@)C:
Answer» 9kcal/mol 4.5kcal/mol 8kcal/mol 10kcal/mol Answer :C