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22.6: Multimedia Resources for Chapter 22

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Copy and distribute the lesson worksheets. Ask students to complete the worksheets alone or in pairs as a review of lesson content.

Enthalpy Worksheet

1. The combustion of methane, CH_4, releases 890.4 \ kJ/mol of heat. That is, when one mole of methane is burned, 890.4 \ kJ are given off to the surroundings. This means that the products have 890.4 \ kJ less energy stored in the bonds than the reactants. Thus,  \Delta H for the reaction = - 890.4 \ kJ. A negative symbol for  \Delta H indicates an exothermic reaction.

CH_{4(g)} + 2 \ O_{2(g)} \rightarrow CO_{2(g)} + 2 \ H_2O_{(L)} && \Delta H = - 890.4 \ kJ

A. How much energy is given off when 2.00 \ mol of CH_4 are burned?

B. How much energy is released when 22.4 \ g of CH_4 are burned?

C. If you were to attempt to make 45.0 \ g of methane from CO_2 and H_2O (with O_2 also being produced), how much heat would be absorbed during the reaction?

Use the following heat of formation table in questions 2 – 6.

The Standard Enthalpy and Entropy of Various Substances
Substance \Delta H^o_f \ (kJ/mol) S^o \ (J/K \cdot mol)
C_4H_{10(g)} -126 310
CaC_{2(s)} -63 70.
Ca(OH)_{2(s)} -987 83
C_2H_{2(g)} 227 201
CO_{2(g)} -394 214
H_{2(g)} 0 131
H_2O_{(g)} -242 189
H_2O_{(L)} -286 70.
NH_{3(g)} -46 193
NO_{(g)} 90. 211
NO_{2(g)} 34 240.
N_2O_{(g)} 82 220.
O_{2(g)} 0 205
O_{3(g)} 143 239

2. Using data from the heat of formation table above, calculate the enthalpy of reaction for

3 \ H_{2(g)} + O_{3(g)} \rightarrow 3 \ H_2O_{(g)}.

3. Using data from the heat of formation table above, calculate the heat of reaction for

2 \ NO_{(g)} + O_{2(g)} \rightarrow 2 \ NO_{2(g)}.

4. Using data from the heat of formation table above, calculate the heat of reaction for

N_2O_{(g)} + NO_{2(g)} \rightarrow 3 \ NO_{(g)}. 5. Using data from the heat of formation table above, calculate the heat of reaction for

CaC_{2(s)} + 2 \ H_2O_{(L)} \rightarrow Ca(OH)_{2(s)} + C_2H_{2(g)}. 6. Many cigarette lighters contain liquid butane, C_4H_{10}. Using the heat of formation table above, calculate the quantity of heat produced when 1.0 \ g of gaseous butane is completely combusted in air.

Hess's Law Worksheet

CK-12 Foundation Chemistry

Name______________________ Date_________

Example Problem

Find the  \Delta H for the reaction below, using the following reactions and their  \Delta H values.

N_2H_{4(L)} + H_{2(g)} \rightarrow 2 \ NH_{3(g)}

Given Equations and
Equation  \Delta H \ \text{Value}
N_2H_{4(L)}+ CH_4O_{(L)} \rightarrow CH_2O_{(g)}+ N_{2(g)}+ 3 \ H_{2(g)}  \Delta H = -37 kJ
N_{2(g)}+ 3 \ H_{2(g)} \rightarrow 2 \ NH_{3(g)}  \Delta H = -46 \ kJ
CH_4O_{(L)} \rightarrow CH_2O_{(g)}+ H_{2(g)}  \Delta H = -65 \ kJ

Solution

Solution Arrangement
Changes Equation  \Delta H \ \text{Value}
Keep Same N_2H_{4(L)}+ CH_4O_{(L)} \rightarrow CH_2O_{(g)}+ N_{2(g)}+ 3 \ H_{2(g)}  \Delta H = -37 \ kJ
Keep Same N_{2(g)}+ 3 \ H_{2(g)} \rightarrow 2 \ NH_{3(g)}  \Delta H = -46 \ kJ
Reverse CH_2O_{(g)}+ H_{2(g)} \rightarrow CH_4O_{(L)}  \Delta H = +65 \ kJ

\text{Sum} \quad N_2H_{4(L)} + H_{2(g)} \rightarrow 2 \ NH_{3(g)} && \Delta H = -18 \ kJ

Exercises

1. Find the  \Delta H for the reaction below, using the following reactions and their  \Delta H values.

H_2SO_{4(L)} \rightarrow SO_{3(g)} + H_2O_{(g)}

Given Equations and
Equation  \Delta H \ \text{Value}
H_2S_{(g)}+ 2 \ O_{2(g)} \rightarrow H_2SO_{4(L)}  \Delta H = -235 \ kJ
H_2S_{(g)}+ 2 \ O_{2(g)} \rightarrow SO_{3(g)}+ H_2O_{(L)}  \Delta H = -207 \ kJ
H_2O_{(L)} \rightarrow H_2O_{(g)}  \Delta H = +44 \ kJ

2. Find the  \Delta H for the reaction below, using the following reactions and their  \Delta H values.

4 \ NH_{3(g)} + 5 \ O_{2(g)} \rightarrow 4 \ NO_{(g)} + 6 \ H_2O_{(g)}

Given Equations and
Equation  \Delta H \ \text{Value}
N_{2(g)}+ O_{2(g)} \rightarrow 2 \ NO_{(g)}  \Delta H = -180.5 \ kJ
N_{2(g)}+ 3 \ H_{2(g)} \rightarrow 2 \ NH_{3(g)}  \Delta H = -91.8 \ kJ
2 \ H_{2(g)}+ O_{2(g)} \rightarrow 2 \ H_2O_{(g)}  \Delta H = -483.6 \ kJ

3. Find the  \Delta H for the reaction below, using the following reactions and their  \Delta H values.

PCl_{5(g)} \rightarrow PCl_{3(g)} + Cl_{2(g)}

Equation  \Delta H \ \text{Value}
P_{4(s)} + 6 \ Cl_{2(g)} \rightarrow 4 \ PCl_{3(g)}  \Delta H = -2439 \ kJ
4 \ PCl_{5(g)} \rightarrow P_{4(s)} + 10 \ Cl_{2(g)}  \Delta H = +3438 \ kJ

4. Find the  \Delta H for the reaction below, using the following reactions and their  \Delta H values.

3 \ H_{2(g)}+ 2 \ C_{(s)}+ \frac {1} {2} \ O_{2(g)} \rightarrow C_2H_5OH_{(L)}

Given Equations and
Equation  \Delta H \ \text{Value}
C_2H_5OH_{(L)}+ 3 \ O_{2(g)} \rightarrow 2 \ CO_{2(g)}+ 3 \ H_2O_{(L)}  \Delta H = -875.0 \ kJ
C_{(s)}+ O_{2(g)} \rightarrow CO_{2(g)}  \Delta H = -394.5 \ kJ
H_{2(g)}+ \frac {1} {2} \ O_{2(g)} \rightarrow  H_2O_{(L)}  \Delta H = -285.8 \ kJ

5. Find the  \Delta H for the reaction below, using the following reactions and their  \Delta H values.

2 \ CO_{2(g)} + H_2O_{(g)} \rightarrow C_2H_{2(g)} + \frac {5} {2} \ O_{2(g)}

Given Equations and
Equation  \Delta H \ \text{Value}
C_2H_{2(g)}+ 2 \ H_{2(g)} \rightarrow C_2H_{6(g)}  \Delta H = -94.5 \ kJ
H_2O_{(g)} \rightarrow H_{2(g)}+ \frac {1} {2} \ O_{2(g)}  \Delta H = +71.2 \ kJ
C_2H_{6(g)}+ \frac {7} {2} \ O_{2(g)} \rightarrow 2 \ CO_{2(g)}+ 3 \ H_2O_{(g)}  \Delta H= -283.0 \ kJ

6. Find the  \Delta H for the reaction below, using the following reactions and their  \Delta H values.

 \frac {1} {2} \ H_{2(g)} + \frac {1} {2} \ Cl_{2(g)} \rightarrow HCl_{(g)}

Given Equations and
Equation  \Delta H \ \text{Value}
COCl_{2(g)}+ H_2O_{(L)} \rightarrow CH_2Cl_{2(L)}+O_{2(g)}  \Delta H = +48 \ kJ
2 \ HCl_{(g)}+ \frac {1} {2} \ O_{2(g)} \rightarrow H_2O_{(L)}+ Cl_{2(g)}  \Delta H = +105 \ kJ
CH_2Cl_{2(L)}+ H_{2(g)}+ \frac {3} {2} \ O_{2(g)} \rightarrow  COCl_{2(g)}+ 2 \ H_2O_{(L)}  \Delta H = -403 \ kJ

Entropy Worksheet

Use the following entropy of formation table in questions 1 – 5.

The Standard Enthalpy and Entropy of Various Substances
Substance  \Delta H^o_f \ (kJ/mol) S^o \ (J/K \cdot mol)
C_4H_{10(g)} -126 310
CaC_{2(s)} -63 70.
Ca(OH)_{2(s)} -987 83
C_2H_{2(g)} 227 201
CO_{2(g)} -394 214
H_{2(g)} 0 131
H_2O_{(g)} -242 189
H_2O_{(L)} -286 70.
NH_{3(g)} -46 193
NO_{(g)} 90. 211
NO_{2(g)} 34 240.
N_2O_{(g)} 82 220.
O_{2(g)} 0 205
O_{3(g)} 143 239

1. Using data from the entropy of formation table above, calculate the entropy of reaction for

3 \ H_{2(g)} + O_{3(g)} \rightarrow 3 \ H_2O_{(g)}.

2. Using data from the entropy of formation table above, calculate the change in entropy for

2 \ NO_{(g)} + O_{2(g)} \rightarrow 2 \ NO_{2(g)}.

3. Using data from the heat of formation table above, calculate the  \Delta S^o for

N_2O_{(g)} + NO_{2(g)} \rightarrow 3 \ NO_{(g)}. 4. Using data from the entropy of formation table above, calculate the heat of reaction for

CaC_{2(s)} + 2 \ H_2O_{(L)} \rightarrow Ca(OH)_{2(s)} + C_2H_{2(g)}. 5. Using the entropy of formation table above, calculate the change in entropy for the following reaction.

C_4H_{10(g)} + \frac {13} {2} \ O_{2(g)} \rightarrow 4 \ CO_{2(g)} + 5 \ H_2O_{(g)}

Enthalpy, Entropy, and Free Energy Worksheet

CK-12 Foundation Chemistry

Name______________________ Date_________

1. As the amount of energy required to decompose a compound increases, the thermodynamic stability of the compound _____________.

A. increases

B. decreases

C. remains constant

D. varies randomly

2. The enthalpy of formation for a free element is

A. 0 \ kJ/mol.

B. 1 \ kJ/mol.

C. 10 \ kJ/mol.

D. -100 \ kJ/mol.

E. variable.

Questions 3 and 4 relate to the following equation and  \Delta H_R value.

2 \ HgO_{(s)} \rightarrow 2 \ Hg_{(L)} + O_{2(g)} && \Delta H_R = +181.7 \ kJ

3. Which of the following can definitely be concluded from the equation and heat of reaction above?

A. The reaction is spontaneous.

B. The reaction is non-spontaneous.

C. The reaction is endothermic.

D. The reaction is exothermic.

E. None of these.

4. From the equation and heat of reaction above, what is the  \Delta H_f of HgO?

A. 181.7 \ kJ/mol

B. -181.7 \ kJ/mol

C. 0 \ kJ/mol

D. 90.9 \ kJ/mol

E. -90.9 \ kJ/mol

5. Which of the following four substances is the most thermodynamically stable? Use the data in the Thermodynamic Data Table at the bottom of the worksheet.

A. NH_{3(g)}

B. CO_{2(g)}

C. H_2O_{(L)}

D. NO_{(g)}

6. The free energy of a reaction is the combination of _________ and _________.

A. heat and work

B. pressure and volume

C. enthalpy and entropy

D. internal energy and PV

E. None of these.

7. All reactions that occur spontaneously must have a negative _________.

A. T \Delta S

B.  \Delta G

C.  \Delta H

D.  \Delta S

E. All of these.

Questions 8, 9, 10, and 11, relate to the equation shown below.

4 \ NH_{3(g)} + 5 \ CO_{2(g)} \rightarrow 6 \ H_2O_{(L)} + 4 \ NO_{(g)}

8. Use the data in the Thermodynamic Data Table at the bottom of this worksheet to find the  \Delta H_R for the reaction above?

A. +92.8 \ kJ

B. -92.8 \ kJ

C.  -806.3 \ kJ

D.  +806.3 \ kJ

E. None of these.

9. Use the data in the Thermodynamic Data Table at the bottom of this worksheet to find the  \Delta G_R for the reaction above?

A. -981.6 \ kJ

B. +981.6 \ kJ

C. -269.0 \ kJ

D. +269.0 \ kJ

E. None of these.

10. Use the data in the Thermodynamic Data Table at the bottom of this worksheet to find the  \Delta S_R for the reaction above?

A. -575.9 \ J/^o

B. +575.9 \ J/^o

C. -1419.1 \ J/^o

D. +1419.1 \ J/^o

E. None of these.

11. Use the  \Delta H_R you found in question 6 and the  \Delta S_R you found in question 8 to calculate  \Delta G_R for this reaction.

A. 634.7 \ kJ

B. -634.7 \ kJ

C. 977.9 \ kJ

D. -977.9 \ kJ

E. None of these.

12. Find  \Delta S for the reaction, 2 \ NO_{(g)} + O_{2(g)} \rightarrow 2 \ NO_{2(g)}.

A.  -146.5 \ J/K

B. +146.5 \ J/K

C. -16.5 \ J/K

D. +16.5 \ J/K

E. None of these.

13. Find  \Delta G_R for the reaction, 2 \ H_2O_{(g)} + 2 \ F_{2(g)} \rightarrow O_{2(g)} + 4 \ HF_{(g)}.

A. -1550.0 \ kJ

B. +1550.0 \ kJ

C. -635.6 \ kJ

D. +635.6 \ kJ

E. None of these.

14. What is the change in enthalpy for 4 \ Al_{(s)} + 3 \ O_{2(g)} \rightarrow 2 \ Al_2O_{3(s)}?

A. 0 \ kJ

B. -1657.7 \ kJ

C. +1657.7 \ kJ

D. +3351.4 \ kJ

E. -3351.4 \ kJ

15. What is the change in entropy for 4 \ Al_{(s)} + 3 \ O_{2(g)} \rightarrow 2 \ Al_2O_{3(s)}?

A. 0 \ J/K

B. -626.7 \ J/K

C. +626.7 \ J/K

D. -500.0 \ J/K

E. +500.0 \ J/K

16. Use the results from questions 14 and 15 to determine under what conditions this reaction will be spontaneous.

A. This reaction will be spontaneous at all temperatures.

B. This reaction will never be spontaneous at any temperature.

C. This reaction will be spontaneous at high temperatures.

D. This reaction will be spontaneous at low temperatures.

Thermodynamic Properties of Some Substances (at
Substance  \Delta H_f^o \ (kJ/mol)  \Delta G_f^o \ (kJ/mol) S^o \ (J/mol \cdot K)
Al_{(s)}  0  0  +28.3
Al_2O_{3(s)}  -1675.7  -1582.3  +50.9
CO_{(g)}  -110.5  -137.2  +197.7
CO_{2(g)}  -393.5  -394.4  +213.7
F_{2(g)}  0  0  +202.8
HF_{(g)}  -271.1  -273.2  +173.8
H_2O_{(L)}  -285.8  -237.1  +69.9
H_2O_{(g)}  -241.8  -228.6  +188.8
NH_{3(g)}  -46.1  -16.5  +192.5
NO_{(g)}  +90.3  +86.6  +210.8
NO_{2(g)}  +33.2  +51.3  +240.1
O_{2(g)}  0  0  +205.1

Answers to Worksheets

  • The worksheet answer keys are available upon request. Please send an email to teachers-requests@ck12.org to request the worksheet answer keys.

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Aug 18, 2012

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Jul 21, 2014
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