1. compound a decomposes at room temperature in an exothermic reaction while compound b requires...
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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
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Ene
rgy
Ene
rgy
Reaction progress Reaction progress
Compound A Compound B
Exothermic Endothermic
Exothermic: Reactants → Products + kJ
Endothermic: Reactants + kJ → Products
(Energy “exits” or is released)
(Energy “enters” or is required)
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Heat = 400.0 g x 80.0 oC x 4.18 J/goC
Heat = 133760 J (gained by H2O)
2. A 500.0 g piece of iron is heated in a flame and dropped into 400.0 g of water at 10.0 oC. The temperature of the water rises to 90.0 oC. How hot wasthe iron when it was first removed from the flame?(Specific heat of iron = 0.473 J/goC)
Heat gained by H2O = Heat lost by metal
First, find the heat gained by the water :
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133760 J = 500.0 g x ∆T x 0.473 J/goC
566 oC = ∆T
Heat gained by H2O = Heat lost by metal
90.0oC + 566oC = 656oC = Initial temp.
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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.NH4NO3 → N2O + 2 H2O
NH4NO3 → N2O + 2 H2O + ? kJ
Exothermic
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2.50 g NH4NO3 1 mol = 0.0313 mol 80.0 g
1.16 kJ = 37.1 kJ / mol NH4NO3
0.0313 mol NH4NO3
NH4NO3 → N2O + 2 H2O + ? kJ
NH4NO3 → N2O + 2 H2O + 37.1 kJ