Honors Chemistry 2017-2018 WS 8.9 More Hess’ Law A. 2 Mg (s) + SiCl4 (l) Si (s) + 2 MgCl2 (s) → SiCl4 (l) Si (s) + 2 Cl2 (g) = +687 kJ H → Mg (s) + Cl2 (g) MgCl2 (s) = -641 kJ H → B. N2 (g) + 2 H2 (g) N2H4 (l) → H2 (g) + 1/2 02 (g) H20 (g) = -242 kJ H → N2 (g) + 2 H20 (g) N2H4 (l) + 02 (g) = +534 kJ H → C. CH4 (g) + 2 02 (g) C02 (g) + 2 H20 (l) → C (s) + 2 H2 (g) CH4 (g) =-74.8 kJ H → C (s) + O2 (g) CO2 (g) = -393.5 kJ H → H2 (g) + 1/2 O2 (g) H2O (l) = -235.8 kJ H → D. 2 C2H6(g) + 7 02(g) 4 C02(g) + 6 H20(g) → 2 C(s) + 3 H2(g) C2H6(g) = -84.7 kJ H → C(s) + 02(g) C02(g) = -393.5 kJ H → H2(g) + 1/2 02(g) H20(g) H = -241.8 kJ → E. 2 N2O3(g) 2 N2(g) + 3 O2(g) → N2O3(g) NO(g) + NO2(g) = 39.7 kJ H → ½ N2(g) + ½ O2(g) NO(g) = 90.4 kJ H → ½ N2(g) + O2(g) NO2(g) = 33.8 kJ H → 106
Honors Chemistry 2017-2018 WS 8.9 More Hess’ Law A. 2 Mg (s) + SiCl4 (l) → Si (s) + 2 MgCl2 (s) SiCl4 (l) → Si (s) + 2 Cl2 (g) H = +687 kJ Mg (s) + Cl2 (g) → MgCl2 (s) H = -641 kJ B. N2 (g) + 2 H2 (g) → N2H4 (l) H2 (g) + 1/2 02 (g) → H20 (g) H = -242 kJ N2 (g) + 2 H20 (g) → N2H4 (l) + 02 (g) H = +534 kJ C. CH4 (g) + 2 02 (g) → C02 (g) + 2 H20 (l) C (s) + 2 H2 (g) → CH4 (g) H =-74.8 kJ C (s) + O2 (g) → CO2 (g) H = -393.5 kJ H2 (g) + 1/2 O2 (g) → H2O (l) H = -235.8 kJ D. 2 C2H6(g) + 7 02(g) → 4 C02(g) + 6 H20(g) 2 C(s) + 3 H2(g) → C2H6(g) H = -84.7 kJ C(s) + 02(g) → C02(g) H = -393.5 kJ H2(g) + 1/2 02(g) → H20(g) H = -241.8 kJ E. 2 N2O3(g) → 2 N2(g) + 3 O2(g) N2O3(g) → NO(g) + NO2(g) H = 39.7 kJ ½ N2(g) + ½ O2(g) → NO(g) H = 90.4 kJ ½ N2(g) + O2(g) → NO2(g) H = 33.8 kJ 106