[单选题]
Liquid dinitrogen te
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y(tgxrco7a3t //q65w x xg(wu roxide ($N_2O_4$) is converted to gaseous nitrogen dioxide when heated, as shown in the diagram. No other molecules react or form during this reaction.
The standard enthalpy change of the reaction,ΔH$_r^θ$, is +85.8kJmol$^{-1}$.The standard enthalpy of formation of gaseous $NO_2$ , ΔH$_r^θ$($NO_2$), is +33.1kJmol$^{-1}$.
What is the standard enthalpy of formation of liquid $N_2O_4$,ΔH$_r^θ$($N_2O_4$)?