1. Compound A decomposes at room temperature in an exothermic reaction while compound B requires heating before it will decompose in an endothermic reaction. Draw reaction profiles (Energy vs. reaction progress) for both reactions. Write out a general equation relating the reactants, products, and energy. (i.e. on which side does the energy term go) Heat Review

Energy Reaction progress Compound A Compound B ExothermicEndothermic Exothermic: Reactants → Products + kJ Endothermic: Reactants + kJ → Products (Energy “exits” or is released) (Energy “enters” or is required)

Heat = g x 80.0 o C x 4.18 J/g o C Heat = J (gained by H 2 O) 2. A g piece of iron is heated in a flame and dropped into g of water at 10.0 o C. The temperature of the water rises to 90.0 o C. How hot was the iron when it was first removed from the flame? (Specific heat of iron = J/g o C) Heat gained by H 2 O = Heat lost by metal First, find the heat gained by the water :

J = g x ∆T x J/g o C 566 o C = ∆T Heat gained by H 2 O = Heat lost by metal 90.0 o C o C = 656 o C = Initial temp.

3. The decomposition of 2.50 g of ammonium nitrate to form dinitrogen monoxide and water releases 1.16 kJ of heat. Write the balanced equation including the energy term, and indicate whether the reaction is endothermic or exothermic. NH 4 NO 3 → N 2 O + 2 H 2 O NH 4 NO 3 → N 2 O + 2 H 2 O + ? kJ Exothermic

2.50 g NH 4 NO 3 1 mol = mol 80.0 g 1.16 kJ = 37.1 kJ / mol NH 4 NO mol NH 4 NO 3 NH 4 NO 3 → N 2 O + 2 H 2 O + ? kJ NH 4 NO 3 → N 2 O + 2 H 2 O kJ