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Unformatted text preview: Name: ___________________________________ CH101 Hess’s Law – Study Guide section 6.8 in the textbook Hess’s Law If a chemical equation is reversed, then the sign of H is also ___________________. If a chemical equation is multiplied by some factor, then H is also _______________________________. example: if 2 CO(g) + O2 (g) 2 CO2 (g) H = ‐566 kJ then 6 CO(g) + 3 O2 (g) 6 CO2 (g) H = _________ (ans. ‐1698 kJ) If a chemical equation can be expressed as the sum of a series of steps, then H for the overall equation is the ______________________________________________________________________. Watch video tutorial on Blackboard example: if 3 H2(g) + N2(g) 2 NH3(g) H = – 69 kJ 4 H2(g) + 2 NO2(g) N2(g) + 4 H2O(g) H = – 255 kJ What is H for the following reaction? 7 H2(g) + 2 NO2(g) 2 NH3(g) + 4 H2O(g) H = _________. (ans:– 324 kJ) End of Chapter Practice Problems Tro First Edition: #67, 69, 71 Tro Second Edition: #75, 77, 79 answers are located in Appendix III of the textbook Take the Quiz on Blackboard ...
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- Spring '11