Thermodynamics, 5th Edition

(3.6.19)

Set at zero the standard enthalpies of the elements; then employ the quantities $\Delta {\tilde{H}}_{f,i}^0=50.42\mathrm{kJ}/\mathrm{mol}$ and −285.84 kJ/mol for hydrazine and water, respectively at 298 K and 1 bar. On adding up these values algebraically (with due regard to the fact that the v_i for reagents are negative), one finds that $\Delta {\tilde{H}}_{RX}^0=-622.09\mathrm{kJ}/\mathrm{mol}$. Here the “/mol” designation indicates that the calculation applies to 1 mol of advancement of the reaction as written ...