1. Thermochemical Equations
17.2
Thermochemical Equations
Thermochemical Equations
How can you express the enthalpy change for a reaction in a chemical equation?

2. Thermochemical Equations
17.2
Thermochemical Equations
In a chemical equation, the enthalpy change for the reaction can be written as either a reactant or a product.

3. Thermochemical Equations
17.2
Thermochemical Equations
A chemical equation that includes the enthalpy change is called a thermochemical equation.

4. Thermochemical Equations
17.2
Thermochemical Equations
The heat of reaction is the enthalpy change for the chemical equation exactly as it is written.

5. Thermochemical Equations
17.2
Thermochemical Equations
Exothermic Reaction
These enthalpy diagrams show exothermic and endothermic processes: a) the reaction of calcium oxide and water and b) the decomposition of sodium bicarbonate. Identifying In which case is the enthalpy of the reactant(s) higher than that of the product(s)?

6. Thermochemical Equations
17.2
Thermochemical Equations
Endothermic Reaction
These enthalpy diagrams show exothermic and endothermic processes: a) the reaction of calcium oxide and water and b) the decomposition of sodium bicarbonate. Identifying In which case is the enthalpy of the reactant(s) higher than that of the product(s)?

7. Thermochemical Equations
Simulation 22
Simulate a combustion reaction and compare the ∆H results for several compounds.

8. 17.3

9. 17.3

10. 17.3

11. 17.3

12. for Sample Problem 17.3
Problem Solving Solve Problem 15 with the help of an interactive guided tutorial.

13. Thermochemical Equations
17.2
Thermochemical Equations

14. Thermochemical Equations
17.2
Thermochemical Equations
The heat of combustion is the heat of reaction for the complete burning of one mole of a substance.
The combustion of natural gas is an exothermic reaction. As bonds in methane (the main component of natural gas) and oxygen are broken and bonds in carbon dioxide and water are formed, large amounts of energy are released.

15. 17.2 Section Quiz.
17.2.

16. the enthalpy change of the reaction in the calorimeter.
17.2 Section Quiz.
1. The change in temperature recorded by the thermometer in a calorimeter is a measurement of
the enthalpy change of the reaction in the calorimeter.
the specific heat of each compound in a calorimeter.
the physical states of the reactants in a colorimeter.
the heat of combustion for one substance in a calorimeter.

17. 17.2 Section Quiz.
2. For the reaction CaO(s) + H2O(l) Ca(OH)2(s),  H = 65.2 kJ. This means that 62.5 kJ of heat is __________ during the process.
absorbed
destroyed
changed to mass
released

18. 17.2 Section Quiz.
3. How much heat is absorbed by 325 g of water if its temperature changes from 17.0°C to 43.5°C? The specific heat of water is J/g°C.
2.00 kJ
3.60 kJ
36.0 kJ
360 kJ

19. 17.2 Section Quiz.
4. Which of the following is a thermochemical equation for an endothermic reaction?
CH4(g) + 2O2(g)  CO2(g) + 2H2O(g) kJ
241.8 kJ + 2H2O(l) 2H2(g) + O2(g)
CaO(s) + H2O(l)  Ca(OH)2(s) kJ
2NaHCO3(s) 129 kJ Na2CO3(s) + H2O(g) + CO2(g)

20. 17.2 Section Quiz.
5. Oxygen is necessary for releasing energy from glucose in organisms. How many kJ of heat are produced when 2.24 mol glucose reacts with an excess of oxygen?
C6H12O6(s) + 6O2(g)  6CO2(g) + 6H2O(g) kJ/mol
4.66 kJ
9.31 kJ
1048 kJ
6290 kJ

21. END OF SHOW