As always… OWL Lon-Capa assignments Lecture videos Textbook Read Do text homework

Clicker Question The following chemical reaction is exothermic: A2 + B2  2AB. This means: more stable higher average bond energies a) Reactants Reactants b) Reactants Products c) Products Products d) Products Reactants e) I do not know.

Clicker Question Use the following data for methanol (CH3OH):   ΔHfusion = 3.18 kJ/mol at –97.6°C ΔHvaporization = 35.3 kJ/mol at 64.7°C Determine ΔE (kJ/mol) for methanol freezing at –97.6°C. a) 1.72 b) –4.64 c) 4.64 d) 3.18 e) –3.18

Clicker Question Use the following data for methanol (CH3OH):   ΔHfusion = 3.18 kJ/mol at –97.6°C ΔHvaporization = 35.3 kJ/mol at 64.7°C Determine ΔE (kJ/mol) for methanol vaporizing at 64.7°C. a) 32.5 b) 35.3 c) –35.3 d) 38.1 e) –38.1

Determining Hrxn Since H = qp, determine the heat given off or required at constant pressure by measuring temperatures. This is termed calorimetry. Since energy is conserved, we can often determine Hrxn for one reaction given values of Hrxn for others. Uses the principle in Hess’s Law. Use standard enthalpies of formations for reactants and products (we have tables of these).

A Coffee-Cup Calorimeter Made of Two Styrofoam Cups

Bomb Calorimeter (constant V)