Lon-Capa 4th HW assignment due Friday, 10/7, 5 pm. It is open now. 3rd Quiz due Sunday, 10/9 by 10 pm. It will open Friday, 10/7 at 5 pm. 5th HW assignment is also open! Three new videos (for Section 9.3). Please watch by Friday.

Hess’s Law Due to first law and H being a state function. If a reaction is reversed, the sign of H is also reversed The magnitude of ΔH is directly proportional to the quantities of reactants and products in a reaction. That is, if the coefficients in a balanced equation are multiplied by an integer, the value of H is multiplied by the same integer.

Clicker Question Given the following data 2NH3(g)  N2(g) + 3H2(g) H = 92kJ 2H2(g) + O2(g)  2H2O(g) H = -484kJ Determine ΔH for 2N2(g) + 6H2O(g)  3O2(g) + 4NH3(g) a) -1268 kJ b) 1268 kJ c) 1636 kJ d) -1636 kJ e) I did not/cannot get any of these answers.

Pathway for the Combustion of Methane

Schematic Diagram of Energy Changes

Chapter 9: Problem #117 This problem is an application of Hess’s law, although it may not be obvious upon reading it.