1. HW 12-8 Enthalpy and Stoichiometry Problem Set

2. 2 H2 + O2 → 2 H2O ∆H = -572 kJ can also be written as:
Balanced chemical equations link moles of reactants, products, and heat energy absorbed or released
2 H2 + O2 → 2 H2O ∆H = -572 kJ
can also be written as:
2 H2 + O2 → 2 H2O kJ
Endothermic or Exothermic?
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Eggosthermic!

3. Reaction Recipes can be scaled up or down
2 moles H2 + 1 mole O2 → 2 moles H2O kJ ½ x recipe: 1 moles H2 + 1/2 mole O2 → moles H2O + kJ 2x recipe: 4 moles H2 + 2 mole O2 → moles H2O + kJ 1
286 4
1144

4. Calculate heat released when 8.08 g H2 burns in excess O2
2 H2 + O2 → 2 H2O kJ
8.08 g H2 ( ( ) )
1 mole H2
- 572 kJ
2.02 g H2
2 mole H2
= kJ = kJ (3 SF)

5. Calculate heat released when 9.50 g Al reacts with excess Fe2O3
2 Al + Fe2O3 → Al2O3 +2 Fe ∆H = -850 kJ
9.50 g Al
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1 mole Al
- 850kJ
27.0 g Al
2 mole Al
= kJ (3 SF)

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