1. DO NOW: (on the back of your notes)
How many kilojoules of heat are produced when 34.0 g of Fe2O3 reacts with an excess of CO according to the following reaction?
Fe2O CO  2 Fe CO H = kJ

2. Unit: Thermochemistry
Notes
Unit: Thermochemistry
Limiting Reactants and Thermochemical
Equations

3. After today you will be able to…
Use thermochemical equations to calculate limiting reactant

4. Recall, a limiting reactant is the reactant which yields the smaller amount of product.
Energy in a chemical reaction can also help to determine which reactant limits the amount of product that can be made.

5. Example: How much energy is used when 14
Example: How much energy is used when 14.3 moles of hydrosulfuric acid reacts with 17.1 moles of oxygen gas? 2H2S + 3O KJ  2SO2 + 2H2O 14.3 mol H2S x _________ = 17.1 mol O2 x ________ =
K: 14.3 mol H2S
U: ? kJ
+ 175 kJ
+1250 kJ
2 mol H2S
K: 17.1 mol O2
U: ? kJ
Used:
+ 175 kJ
+998 kJ
3 mol O2

6. Example: How much energy is produced when 13. 11g of tin reacts with 2
Example: How much energy is produced when 13.11g of tin reacts with 2.715g of nitrogen? __ Sn + __ N2  __ Sn3N KJ gSn x _________ x ________ = gN2 x ________ x ________ = 3 2 1
K: gSn
U: ? kJ
Produced:
1 mol Sn
-632 kJ kJ
gSn
3 mol Sn
K: gN2
U: ? kJ
1 mol N2
-632 kJ kJ
28.02 gN2
2 mol N2

7. Questions? Complete WS

8. SILENCE IS GOLD-EN