1. Thermochemistry Practice

2. A) How much energy did the aluminum release? Caluminum = 0.897 J/g °C
A 10.g piece of 500.0°C aluminum is dropped into a calorimeter with 100.g of water. After reaching equilibrium the temperature of the water is 50.0°C.
A) How much energy did the aluminum release? Caluminum = J/g °C
B) What was the original temperature of the water? Cwater = 4.18 J/g °C
-4.0 x 103 J
40.3°C

3. 2) Consider the combustion:
C5H12(g) + 8O2(g) → 5CO2(g) + 6H2O(l) ΔH = − kJ/mol
If grams of oxygen was consumed, how much energy was released? kJ

4. 3) The specific heat of lead is 0. 129 J/g°C
3) The specific heat of lead is J/g°C. Find the amount of heat released when g of lead is cooled from 25.6°C to 21.4°C.
-152 J

5. 4) If the molar heat of fusion of water is 6
4) If the molar heat of fusion of water is 6.02 kJ/mol, how much heat is needed to melt 54.8 g of ice?
18.3 kJ

6. Cice= 2.108 J/g°C Cwater= 4.186 J/g°C Csteam= 1.996 J/g°C ∆Hfus = 6.02 kJ/mol, ∆Hvap = 40.7 kJ/mol
5) What is the change in enthalpy when 13.5g of steam at °C is cooled to a solid at -8.00°C?
-41.3 kJ

7. 6) A 28. 2 g sample of nickel is placed in a beaker containing 250
6) A 28.2 g sample of nickel is placed in a beaker containing mL of water at 99.8°C. The nickel is then placed in a coffee-cup calorimeter containing mL of water at a temperature of 23.5°C. After the metal cools, the final temperature of the calorimeter water is 25.0°C. Calculate the specific heat of the nickel. The specific heat of water is 4.18 J/g °C
0.446 J/g°C

8. 2C(s) + H2(g) ---> C2H2(g) ΔH° = ??? kJ
7) Calculate the enthalpy for this reaction:
2C(s) + H2(g) ---> C2H2(g) ΔH° = ??? kJ
Given the following thermochemical equations:
C2H2(g) + (5/2)O2(g) ---> 2CO2(g) + H2O(ℓ) ΔH° = kJ
C(s) + O2(g) ---> CO2(g) ΔH° = kJ
H2(g) + (1/2)O2(g) ---> H2O(ℓ) ΔH° = kJ
227 kJ

9. 8) When a 95 g sample of aluminum absorbs 7355 J of heat energy, its temperature increases from 23°C to 105°C. Find the specific heat of aluminum. Include the correct unit.
0.94 J/g°C

10. 9) 2NO(g) + O2(g) → 2NO2(g) ∆H = -114
9) 2NO(g) + O2(g) → 2NO2(g) ∆H = kJ/mol Determine the amount of heat released when g of NO2 gas is formed. kJ

11. 10) If I have a bottle of compound X at a pressure of 45 atm and temperature of 1000 C, what will happen if I raise the temperature to 4000 C?
Sublimation

12. 11) Given that the molar heat of vaporization of benzene (C6H6) is 30
11) Given that the molar heat of vaporization of benzene (C6H6) is 30.8 kJ/mol (∆Hvap = 30.8 kJ/mol), how much energy is needed to convert 98.2 g of liquid benzene to a gas.
38.7 kJ

13. 4.71 kJ Cice= 2.108 J/g°C Cwater= 4.186 J/g°C Csteam= 1.996 J/g°C
∆Hfus = 6.02 kJ/mol ∆Hvap= 40.7 kJ/mol
12) What is the change in enthalpy when 10.0 g of ice at °C is converted to liquid water and heated to 25.0°C?
4.71 kJ

14. 13) Use the following data to determine the specific heat of zinc
Mass of water in Calorimeter
100.0 g
Initial temperature of water
23.0°C
Final temperature of water
25.4°C
Specific heat of water
4.18 J/g°C
Mass of Zinc
60.87 g
Initial temperature of zinc
89.8°C
0.256 J/g°C

15. 14) Find the ΔH for the overall reaction below, given the following reactions and subsequent ΔH values: H2SO4(l)  →  SO3(g)  +  H2O(g)
H2S(g)  +  2O2(g)  →  H2SO4(l)           ΔH = kJ H2S(g)  +  2O2(g)  →  SO3 (g)  +  H2O(l)       ΔH = -207 kJ H2O(l)  →  H2O(g)                                         ΔH = 44 kJ
73 kJ

16. 15) What mass of iron must be reacted with excess oxygen to produce kJ of heat based on the reaction:
4Fe(s) + 3O2(g)  2Fe2O3(s) ΔH = kJ
40.77 g

17. 16) When J of heat are applied to a sample of Be its temperature increases from 22°C to 50°C. What is the sample’s mass? The specific heat of Be is J/g°C.
7.8 g

18. 17) The ΔHfus of ethanol (C2H5OH) is 4. 94 kJ/mol
17) The ΔHfus of ethanol (C2H5OH) is 4.94 kJ/mol. How much heat is released when mL of ethanol freezes if the density of ethanol is g/mL
21.15 kJ

19. Cice= 2. 108 J/g°C. Cwater= 4. 186 J/g°C. Csteam= 1
Cice= J/g°C Cwater= J/g°C Csteam= J/g°C ∆Hfus = 6.02 kJ/mol ∆Hvap= 40.7 kJ/mol
18) What is the change in enthalpy when mL of water at 60.00°C is converted to steam and heated to °C ?
9.195 kJ

20. 19) A 55. 0 g sample of a metal with a specific heat of 0
19) A 55.0 g sample of a metal with a specific heat of 0.21 J/g°C was heated and then placed in a calorimeter filled with mL of room temperature water at 24.6 °C. The temperature of the water rose to 26.3°C. What was the initial temperature of the metal? (Cwater = 4.18 J/g°C)
180.1°C

21. 20) What mass of sodium must be reacted with excess water to produce 1000. kJ of heat energy.
2Na(g) + 2H2O(l)  2NaOH(aq) + H2(g) ΔH = -282 kJ
163.0 g

22. Cice= 2. 108 J/g°C. Cwater= 4. 186 J/g°C. Csteam= 1
Cice= J/g°C Cwater= J/g°C Csteam= J/g°C ∆Hfus = 6.02 kJ/mol ∆Hvap= 40.7 kJ/mol
21) What is the change in enthalpy when g of ice at -5.00°C is converted to steam and heated to °C?
97.78 kJ