Chapter 06 – Thermochemistry
Chapter 06
Thermochemistry
1.
Radiant energy is
2. Thermal energy is 4
Chapter 06 – Thermochemistry
3. Chemical energy is
4. Potential energy is
5. Heat is
Chapter 06 – Thermochemistry
6. An endothermic reaction causes the surroundings to
7. An exothermic reaction causes the surroundings to
Chapter 06 – Thermochemistry
8. Aluminum metal has a specific heat of 0.900 J/g·C. Calculate the amount of heat required
to raise the temperature of 10.5 moles of Al from 30.5 C to 225C.
9. Given the specific heat for aluminum is 0.900 J/g·C, how much heat is released when a
3.8 g sample of Al cools from 450.0C to 25C?
Chapter 06 – Thermochemistry
10. Calculate the amount of heat necessary to raise the temperature of 135.0 g of water from
50.4F to 85.0F. The specific heat of water = 4.184 J/g·C.
11. How much heat is required to raise the temperature of 1.5 x 103 g of water from 45F to
130.F? The specific heat of water is 4.184 J/g·C.
Chapter 06 – Thermochemistry
12. Three separate 3.5g blocks of Al, Cu, and Fe at 25C each absorb 0.505 kJ of heat. Which
block reaches the highest temperature? The specific heats of Al, Cu, and Fe are 0.900 J/g·C,
0.385J/g·C, and 0.444 J/g·C, respectively.
13. A beaker contains 115 g of ethanol at 18.2C. If the ethanol absorbs 1125 J of heat
without losing heat to the surroundings, what will be the final temperature of the ethanol? The
specific heat of ethanol is 2.46 J/gC.
Chapter 06 – Thermochemistry
14. A 22.0 g block of copper at 45C absorbs 2.50 kJ of heat. Given the specific heat of Cu is
0.385 J/g·C what will be the final temperature of the Cu?
15. If 10.6 moles of water at 35C absorbs 12.30 kJ, what is the final temperature of the
water? The specific heat of water is 4.184 J/g·C.
Chapter 06 – Thermochemistry
16. A 135 g sample of H2O at 85C is cooled. The water loses a total of 15 kJ of energy in the
cooling process. What is the final temperature of the water? The specific heat of water is
4.184 J/g·C.
17. A piece of copper with a mass of 218 g has a heat capacity of 83.9 J/C. What is the
specific heat of copper?
Chapter 06 – Thermochemistry
18. The specific heat of gold is 0.129 J/g·C. What is the molar heat capacity of gold?
19. Suppose a 50.0 g block of silver (specific heat = 0.2350 J/g·C) at 100C is placed in
contact with a 50.0 g block of iron (specific heat = 0.4494 J/g·C) at 0C, and the two blocks
are insulated from the rest of the universe. The final temperature of the two blocks
Chapter 06 – Thermochemistry
20. When 0.7521 g of benzoic acid was burned in a calorimeter containing 1,000. g of water,
a temperature rise of 3.60C was observed. What is the heat capacity of the bomb calorimeter,
excluding the water? The heat of combustion of benzoic acid is –26.42 kJ/g.
21. Naphthalene combustion can be used to calibrate the heat capacity of a bomb calorimeter.
The heat of combustion of naphthalene is –40.1 kJ/g. When 0.8210 g of naphthalene was
burned in a calorimeter containing 1,000. g of water, a temperature rise of 4.21C was
observed. What is the heat capacity of the bomb calorimeter excluding the water?
Chapter 06 – Thermochemistry
22. Which of the following processes is exothermic?
23.
Which of the following processes is exothermic, given the following:
N2(g) + 2 O2(g) → N2O4(l) H
= 9.67 kJ/mol
N2(g) + 2 O2(g) → 2 NO2(g) H
= 67.70 kJ/mol
Chapter 06 – Thermochemistry
24.
Which of the following processes is endothermic, given the following:
S(s) + O2(g) →SO2(g) H = –299 kJ/mol
S(s) + 3/2 O2(g) →SO3(g) H = –395 kJ/mol
25. Which of the following processes is endothermic?
Chapter 06 – Thermochemistry
26.
A 100. mL sample of 0.200 M aqueous hydrochloric acid is added to 100. mL of 0.200 M aqueous ammonia in a calorimeter
whose heat capacity (excluding any water) is 480. J/K. The following reaction occurs when the two solutions are mixed.
HCl(aq) + NH3(aq) →NH4Cl(aq)
The temperature increase is 2.34C. Calculate H per mole of HCl and NH3 reacted.
27. A 0.1326 g sample of magnesium was burned in an oxygen bomb calorimeter. The total
heat capacity of the calorimeter plus water was 5,760 J/C. If the temperature rise of the
calorimeter with water was 0.570C, calculate the enthalpy of combustion of magnesium.
Mg(s) + 1/2O2(g) →MgO(s)
Chapter 06 – Thermochemistry
28. The reaction that represents the standard enthalpy of formation for acetone (CH3COCH3),
a common ingredient in nail polish remover is:
29. The reaction that represents the standard enthalpy of formation for sucrose (C12H22O11) is:
Chapter 06 – Thermochemistry
30. The reaction that represents the standard enthalpy of formation for benzene (C6H6) is:
Chapter 06 – Thermochemistry
31.
Which of the following has a Hf= 0 kJ/mol?
32.
Which of the following has a Hf= 0 kJ/mol?
Chapter 06 – Thermochemistry
33.
When 0.560 g of Na(s) reacts with excess F2(g) to form NaF(s), 13.8 kJ of heat is evolved at standard-state conditions. What
is the standard enthalpy of formation (Hf) of NaF(s)?
34.
When 18.5 g of HgO(s) is decomposed to form Hg(l) and O2(g), 7.75 kJ of heat is absorbed at standard-state conditions.
What is the standard enthalpy of formation (Hf) of HgO(s)?
Chapter 06 – Thermochemistry
35.
Ethanol undergoes combustion in oxygen to produce carbon dioxide gas and liquid water. The standard heat of combustion of
ethanol, C2H5OH(l), is –1366.8 kJ/mol. Given that Hf[CO2(g)] = –393.5 kJ/mol and Hf[H2O(l)] = –285.8 kJ/mol, what is
the standard enthalpy of formation of ethanol?
36.
Find the standard enthalpy of formation of ethylene, C2H4(g), given the following data: heat of combustion of C2H4(g)= –
1411 kJ/mol; Hf[CO2(g)] = –393.5 kJ/mol; Hf[H2O(l)] = –285.8 kJ/mol.
Chapter 06 – Thermochemistry
37.
Octane (C8H18) undergoes combustion according to the following thermochemical equation:
2C8H18(l) + 25O2(g) → 16CO2(g) + 18H2O(l), Hrxn = –11,020 kJ/mol.
Given that Hf[CO2(g)] = –393.5 kJ/mol and Hf[H2O(l)] = –285.8 kJ/mol, calculate the standard enthalpy of formation of
octane.
38.
Acetylene (C2H2) undergoes combustion in excess oxygen to generate gaseous carbon dioxide and water. Given
Hf[CO2(g)] = –393.5 kJ/mol, Hf[H2O(g)] = –241.8 kJ/mol, and Hf[C2H2(g)] = 226.6 kJ/mol, how much energy is
released (kJ) when 10.5 moles of acetylene is burned?
Chapter 06 – Thermochemistry
39.
Butane (C4H10) undergoes combustion in excess oxygen to generate gaseous carbon dioxide and water. Given Hf[C4H10(g)]
= –124.7 kJ/mol, Hf[CO2(g)] = –393.5 kJ/mol, Hf[H2O(g)] = –241.8 kJ/mol, how much energy is released (kJ) when
8.30 g of butane is burned?
40.
Glycine, C2H5O2N, is important for biological energy. The combustion reaction of glycine is given by the equation
4C2H5O2N(s) + 9O2(g) → 8CO2(g) + 10H2O(l) + 2N2(g) Hrxn = –3857 kJ/mol
Given that Hf[CO2(g)] = –393.5 kJ/mol and Hf[H2O(l)] = –285.8 kJ/mol, calculate the enthalpy of formation of glycine.