Consider the following two reactions carried out at standard conditions: 1

CHEMISTRY · Single correct · A Level · Chemistry · Energetics · Energetics

Problem

Consider the following two reactions carried out at standard conditions: 1. 2NO(g)+O2(g)→2NO2(g)ΔH1∘=−114 kJ2\text{NO}(g)+\text{O}_2(g)\rightarrow 2\text{NO}_2(g)\qquad \Delta H_1^\circ=-114\,\text{kJ} 2. N2O4(g)→2NO2(g)     ΔH2∘=+57 kJ\text{N}_2\text{O}_4(g)\rightarrow 2\text{NO}_2(g)\qquad\;\;\, \Delta H_2^\circ=+57\,\text{kJ} Given ΔHf∘(NO2(g))=−33 kJ mol−1\Delta H_f^\circ\bigl(\text{NO}_2(g)\bigr)=-33\,\text{kJ mol}^{-1}, calculate ΔHf∘(N2O4(g))\Delta H_f^\circ\bigl(\text{N}_2\text{O}_4(g)\bigr). (a) +57 kJ mol−1+57\,\text{kJ mol}^{-1} (b) +123 kJ mol−1+123\,\text{kJ mol}^{-1} (c) −123 kJ mol−1-123\,\text{kJ mol}^{-1} (d) −90 kJ mol−1-90\,\text{kJ mol}^{-1}

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