Download Thermal Chem Review and Key

Ch.10 & 11 Sections 10.3, 10.4, 11.1, 11.2, 11.3 Review
1. What is an exothermic reaction? An endothermic reaction?
2. Compare the potential chemical energy of reactants and products for both endo and exothermic reactions.
(Look at your notes with the chemical potential energy diagrams for endo & exothermic reactions.)
3. Define enthalpy and explain the sign (+ or -) for endo and exothermic reactions.
4. Define calorimetry. What does a calorimeter measure?
5. Define heat.
6. Calculate the heat released during the decomposition of 4.5 moles of H2O2.
2H2O2  2H2O + O2
Ho = -190kJ
7. How much heat is given off when 1.0g of H2O2 decomposes to produce H2O and O2
according to the above equation.
8. How much heat will be transferred if 27.1g of I2 reacts with excess hydrogen according to the
following equation? H2 + I2  2HI
H = 26.5 kJ
9. Is the above reaction endo or exothermic?
10. Energy is ________to break bonds, while energy is ________ to form bonds in a chemical reaction.
11. Define enthalpy.
12. Define calorie.
13. A sample that is completely burned in a calorimeter released 4,500 calories. How many dietary Calories did
is possess?
14. Where did the energy released in an exothermic reaction come from? What happens to the energy absorbed
in an endothermic reaction?
15. What equation is used to calculate the energy involved in a phase change? Does this equation pertain to the
diagonal or plateau sections on your heating and cooling curve?
16. What equation is used to calculate the energy involved in increasing or decreasing the temperature of a
substance? Does this equation pertain to the diagonal or plateau sections on your heating and cooling
curve?
17. What does it mean if a substance is in its “standard state”?
18. How much heat is required to raise 14.2g of iron 35oC? (The specific heat of iron is 0.46 J/g oC)
19. Define molar heat of fusion and solidification.
20. How many grams of ice at 0oC and 101.3kPa could be melted by the addition of 4.25 kJ of heat?
Hfus= 6.01 kJ/mol
21. What are molar heats of vaporization, condensation, and solution?
22. How much heat is absorbed when 45.8 g H2O(l) at 100oC is converted to steam at 100oC?
Hvap= 40.7 kJ/mol
23. How much heat is released when 4.50 mol NaOH(s) is dissolved in H2O? H soln=-445.1 kJ/mol
24. The SI unit of energy and heat is the ______.
25. Study your notes and homework and be able to label a phase diagram..
Chem. 433
Ch. 11 Review
1.
An exothermic reaction releases heat
An endothermic reaction absorbs heat
2.
Endothermic reactions: Potential chemical energy of the reactants is less than that of the products
Exothermic reactions: Potential chemical energy of the reactants is greater than that of the products
3.
Enthalpy is the heat content of a system at constant pressure.
H for exothermic is (-)
H for endothermic is (+)
4.
Calorimetry is the measurement of heat absorbed or released during a chemical reaction.
5.
Heat (q) = the amount of energy transferred from one object to another due to a difference in temperature.
6.
4.5 mol H2O2 x __190 kJ___ 4.1 x 102 kJ
2 mol H2O2
7.
1.0g H2O2 x _1 mol H2O2_ x __190 kJ___ = 2.79 kJ
34.02 g H2O2 2 mol H2O2
8.
27.1g I2 x _1 mol I2_ x 26.5 kJ_ = 0.283 kJ
253.8 g I2 1 mol I2
9.
Endothermic (H is positive)
10.
required, released
11.
Enthalpy is the heat content of a system at constant pressure
H = Hproducts – Hreactants = qrxn = mct
12.
A calorie is the amount of energy required to raise 1g of water by 1 oC.
13.
4,500 cal x 1 Cal = 4.5 Cal.
1,000 cal
14.
Energy released in an exothermic reaction was once stored in the chemical bonds of the reactants.
Energy absorbed in an endothermic reaction is stored in the chemical bonds of the products
15.
q = nHv or q = nHf ; plateaus
16.
q = mCT ; diagonals
17.
The standard state of a substance is its most stable state at 1 atm. and 25 oC.
18.
q= mct = (14.2 g) x (.46 J/goC) x 35 oC = 230 J
19.
The molar heat of fusion (Hfus) is the heat absorbed by one mole of a substance in melting from a solid to a liquid at a
constant temperature.
The molar heat of solidification (Hsolid) is the heat lost when one mole of a liquid solidifies at a constant temperature.
20.
4.25 kJ x _1 mol_ x 18.02 g = 12.7 g
6.01 kJ
1 mol
21.
Molar heat of vaporization is the amount of heat necessary to vaporize one mole of a given liquid at constant temperature.
Molar heat of condensation is the amount of heat released when one mole of vapor condenses at a constant temperature.
Molar heat of solution (Hsoln,) is the heat change caused by dissolution of one mole of a substance.
22.
45.8g H2O x _1 mol x 40.7 kJ_ = 103 kJ
18.02 g
1 mol
23.
4.50 mol x 445.1 kJ = 2003 kJ or 2.00 x 103 kJ
1 mol
24.
Joule (J)
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aved as Thermal chemistry ch.11 review