Slide 1

Energy & StoichiometryExothermic and EndothermicExothermic process heat is released into the surroundingsExo = Exit

Endothermic Process heat is absorbed from the surroundingsEndo = Into

HEAT

HEATThermochemical EquationsIn a thermochemical equation, the energy of change for the reaction can be written as either a reactant or a productEnthalpy: the heat content of a system at constant pressure (H)

Endothermic (positive H)2NaHCO3 + 129kJ Na2CO3 + H2O + CO2Exothermic (negative H)CaO + H2O Ca(OH)2 + 65.2kJ Write the thermochemical equation for the oxidation of Iron (III) if its H= -1652 kJ

Fe(s) + O2(g) Fe2O3(s) + 1652 kJ

How much heat is evolved when 10.00g of Iron is reacted with excess oxygen?

43210.00g Fe55.85g Fe1 mol4 mol Fe1652 kJ=73.97 kJ of heatExoWrite the thermochemical equation for the decomposition of sodium bicarbonate, with a H = + 129 kJ:

2 NaHCO3 + 129kJ Na2CO3(s) + H2O + CO2

How much heat is required to break down 50.0g of sodium bicarbonate?

50.0 g NaHCO383.9 g NaHCO31 mol NaHCO32 mol NaHCO3129 kJ=38.4 kJ of heatEndoWrite the thermochemical equation for a single replacement of calcium oxide and water with a H= - 65.2 kJ:

CaO + H2O Ca(OH)2 + 65.2kJ

How much energy is released when 100 g of calcium oxide reacts?

100 g CaO56.07 g CaO1 mol CaO1 mol CaO65.2 kJ=116 kJ of heatExoWrite the thermochemical equation for the decomposition of magnesium oxide with a H= + 61.5 kJ:

2 MgO + 61.5 2 Mg + O2

How many grams of oxygen are produced when magnesium oxide is decomposed by adding 420 kJ of Energy?

420 kJ 61.5 kJ1 mol O21 mol O231.98 g O2=218 g of O2Endo