1. Energy & Stoichiometry

2. Exothermic and Endothermic
Exothermic process – heat is released into the surroundings
Exo = Exit
Endothermic Process – heat is absorbed from the surroundings
Endo = Into
HEAT
HEAT

3. Thermochemical Equations
In a thermochemical equation, the energy of change for the reaction can be written as either a reactant or a product
Enthalpy: the heat content of a system at constant pressure (ΔH)
Endothermic (positive ΔH)
2NaHCO kJ Na2CO3 + H2O + CO2
Exothermic (negative ΔH)
CaO + H2O Ca(OH) kJ

4. Write the thermochemical equation for the oxidation of Iron (III) if its ΔH= kJ Fe(s) + O2(g)→ Fe2O3(s) kJ How much heat is evolved when 10.00g of Iron is reacted with excess oxygen?
Exo 4 3 2
10.00g Fe
1 mol
1652 kJ
=73.97 kJ of heat
55.85g Fe
4 mol Fe

5. Write the thermochemical equation for the decomposition of sodium bicarbonate, with a ΔH = kJ: 2 NaHCO kJ → Na2CO3(s) + H2O + CO2 How much heat is required to break down 50.0g of sodium bicarbonate?
Endo
1 mol NaHCO3
50.0 g NaHCO3
129 kJ
83.9 g NaHCO3
2 mol NaHCO3
=38.4 kJ of heat

6. Write the thermochemical equation for a single replacement of calcium oxide and water with a ΔH= kJ: CaO + H2O → Ca(OH) kJ How much energy is released when 100 g of calcium oxide reacts?
Exo
100 g CaO
1 mol CaO
65.2 kJ
56.07 g CaO
1 mol CaO
=116 kJ of heat

7. Write the thermochemical equation for the decomposition of magnesium oxide with a ΔH= kJ: 2 MgO → 2 Mg + O2 How many grams of oxygen are produced when magnesium oxide is decomposed by adding 420 kJ of Energy?
Endo
420 kJ
1 mol O2
31.98 g O2
=218 g of O2
61.5 kJ
1 mol O2