The heat of vaporization of water at the normal boiling

You are calculating DE in a chemistry problem. What if you confuse the system and the surroundings? How would this affect the magnitude of the answer you calculate? The sign?

What if Hesss law were not true? What are some possible repercussions this would have?

For DHreaction calculations we define DH8f for an element in its standard state as zero. What if we define DH8f for an element in its standard state as 10 kJ/mol? How would this affect your determination of DHrxn? Provide support for your answer with a sample calculation.

Objects placed together eventually reach the same temperature. When you go into a room and touch a piece of metal in that room, it feels colder than a piece of plastic. Explain

What is meant by the term lower in energy? Which is lower in energy, a mixture of hydrogen and oxygen gases or liquid water? How do you know? Which of the two is more stable? How do you know?

A fire is started in a fireplace by striking a match and lighting crumpled paper under some logs. Explain the energy transfers in this scenario using the terms exothermic, endothermic, system, surroundings, potential energy, and kinetic energy.

Liquid water turns to ice. Is this process endothermic or exothermic? Explain what is occurring using the terms system, surroundings, heat, potential energy, and kinetic energy

Consider the following statements: Heat is a form of energy, and energy is conserved. The heat lost by the system must be equal to the amount of heat gained by the surroundings. Therefore, heat is conserved. Indicate everything you think is correct in these statements and everything you think is incorrect in these statements. Correct the incorrect statements and explain.

Photosynthetic plants use the following reaction to produce glucose, cellulose, and more: 6CO2(g) 1 6H2O(l) 88n C6H12O6(s) 1 6O2(g) How might extensive destruction of forests exacerbate the greenhouse effect?

Photosynthetic plants use the following reaction to produce glucose, cellulose, and more: 6CO2(g) 1 6H2O(l) 88n C6H12O6(s) 1 6O2(g) How might extensive destruction of forests exacerbate the greenhouse effect?

Predict the signs of q and w for the process of boiling water.

Hesss law is really just another statement of the first law of thermodynamics. Explain.

In the equation w 5 2PDV, why is there a negative sign?

Why is Cp larger than Cv? Provide a conceptual rationale

You have an ideal gas with an initial volume of 1.0 L and initial pressure of 1.0 atm. You decide to change the conditions such that Pfinal 5 2.0 atm and Vfinal 5 2.0 L. To make things more interesting, you and a friend each carry out this change in two steps. You first change the volume so that at one point P 5 1.0 atm and V 5 2.0 atm. Your friend first changes the pressure so that at one point P 5 2.0 atm and V 5 1.0 atm. Both of you, of course, end up with the same final conditions after the second step. a. How should your DEs, DHs, qs, and ws compare with those of your friend? Why? b. Calculate DE, DH, q, and w for each case. Do they make sense? Explain.

When is DH 5 5 2RT? When is DE 5 5 2RT? When is DH 5 3 2RT? When is DE 5 3 2RT? When is DH 5 DE? What does this say, if anything, about DE and DH as state functions?

For a liquid, which would you expect to be larger: DHvaporization or DHfusion? Explain

Consider the accompanying diagram. Ball A is allowed to fall and strike ball B. Assume that all of ball As energy is transferred to ball B at point I and that there is no loss of energy to other sources. Calculate the kinetic energy and the potential energy of ball B at point II. For a falling object, the potential energy is given by PE 5 mgz, where m is the mass in kilograms, g is the gravitational constant (9.81 m/s2), and z is the distance in meters. B 4.00 kg I II 10.0 m 3.00 m A 2.00 kg

Consider the following potential energy diagrams for two different reactions. Reactants Products Potential energy a. Products Reactants Potential energy b. Which plot represents an exothermic reaction? In plot a, do the reactants on average have stronger or weaker bonds than the products? In plot b, reactants must gain potential energy to convert to products. How does this occur?

Consider an airplane trip from Chicago, Illinois, to Denver, Colorado. List some path-dependent functions and some state functions for the plane trip. 18. Consider the following diagram when answering the questions on the next page. A B A B Initial Final Held in p a. Compare balls A and B in terms of potential energy in both the initial and final setups. b. Ball A has stopped moving in the final setup, but energy must be conserved. What happened to the potential energy of ball A?

Assuming gasoline is pure C8H18(l), predict the signs of q and w for the process of combusting gasoline into CO2(g) and H2O(g)

Consider 2.00 moles of an ideal gas that is taken from state A (PA 5 2.00 atm, VA 5 10.0 L) to state B (PB 5 1.00 atm, VB 5 30.0 L) by two different pathways. VC 5 30.0 L 1 PC 5 2.00 atm 2 State A State B VA 5 10.0 L VB 5 30.0 L PA 5 2.00 atm 3 4 PB 5 1.00 atm VD 5 10.0 L PD 5 1.00 atm These pathways are summarized in the following graph of P versus V: P (atm) 0 V (L) A B 1 C D 4 3 2 1 2 10 20 30 Calculate the work (in units of J) associated with the two pathways. Is work a state function? Explain

A sample of an ideal gas at 15.0 atm and 10.0 L is allowed to expand against a constant external pressure of 2.00 atm at a constant temperature. Calculate the work in units of kJ for the gas expansion. (Hint: Boyles law applies.)

A piston performs work of 210. L ? atm on the surroundings, while the cylinder in which it is placed expands from 10. L to 25 L. At the same time, 45 J of heat is transferred from the surroundings to the system. Against what pressure was the piston working?

A system undergoes a process consisting of the following two steps: Step 1: The system absorbs 72 J of heat while 35 J of work is done on it. Step 2: The system absorbs 35 J of heat while performing 72 J of work. Calculate DE for the overall process.

Calculate the internal energy change for each of the following. a. One hundred (100.) joules of work are required to compress a gas. At the same time, the gas releases 23 J of heat. b. A piston is compressed from a volume of 8.30 L to 2.80 L against a constant pressure of 1.90 atm. In the process, there is a heat gain by the system of 350. J. c. A piston expands against 1.00 atm of pressure from 11.2 L to 29.1 L. In the process, 1037 J of heat is absorbed.

A balloon filled with 39.1 moles of helium has a volume of 876 L at 0.08C and 1.00 atm pressure. At constant pressure, the temperature of the balloon is increased to 38.08C, causing the balloon to expand to a volume of 998 L. Calculate q, w, and DE for the helium in the balloon. (The molar heat capacity for helium gas is 20.8 J 8C21 mol21.)

Consider a mixture of air and gasoline vapor in a cylinder with a piston. The original volume is 40. cm3. If the combustion of this mixture releases 950. J of energy, to what volume will the gases expand against a constant pressure of 650. torr if all the energy of combustion is converted into work to push back the piston?

One mole of H2O(g) at 1.00 atm and 100.8C occupies a volume of 30.6 L. When 1 mole of H2O(g) is condensed to 1 mole of H2O(l) at 1.00 atm and 100.8C, 40.66 kJ of heat is released. If the density of H2O(l) at this temperature and pressure is 0.996 g/cm3, calculate DE for the condensation of 1 mole of water at 1.00 atm and 100.8C

As a system increases in volume, it absorbs 52.5 J of energy in the form of heat from the surroundings. The piston is working against a pressure of 0.500 atm. The final volume of the system is 58.0 L. What was the initial volume of the system if the internal energy of the system decreased by 102.5 J?

What is the difference between DH and DE at constant P?

The enthalpy change for a reaction is a state function and it is an extensive property. Explain

One of the components of polluted air is NO. It is formed in the high-temperature environment of internal combustion engines by the following reaction: N2 1g2 1 O2 1g2 h 2NO1g2 DH 5 180 kJ Why are high temperatures needed to convert N2 and O2 to NO?

Are the following processes exothermic or endothermic? a. the combustion of gasoline in a car engine b. water condensing on a cold pipe c. CO2(s) 88n CO2(g) d. F2(g) 88n 2F(g

The reaction SO3(g) 1 H2O(l) 88n H2SO4(aq) is the last step in the commercial production of sulfuric acid. The enthalpy change for this reaction is 2227 kJ. In the design of a sulfuric acid plant, is it necessary to provide for heating or cooling of the reaction mixture? Explain your answer

Consider the following reaction: 2H2(g) 1 O2(g) 88n 2H2O(l) DH 5 2572 kJ a. How much heat is evolved for the production of 1.00 mole H2O(l)? b. How much heat is evolved when 4.03 g hydrogen is reacted with excess oxygen? c. How much heat is evolved when 186 g oxygen is reacted with excess hydrogen? d. The total volume of hydrogen gas needed to fill the Hindenburg was 2.0 3 108 L at 1.0 atm and 258C. How much heat was evolved when the Hindenburg exploded, assuming all of the hydrogen reacted?

The overall reaction in a commercial heat pack can be represented as 4Fe(s) 1 3O2(g) 88n 2Fe2O3(s) DH 5 21652 kJ a. How much heat is released when 4.00 moles of iron is reacted with excess O2? b. How much heat is released when 1.00 mole of Fe2O3 is produced? c. How much heat is released when 1.00 g iron is reacted with excess O2? d. How much heat is released when 10.0 g Fe and 2.00 g O2 are reacted?

Consider the combustion of propane: C3H8(g) 1 5O2(g) 88n 3CO2(g) 1 4H2O(l) DH 5 22221 kJ Assume that all the heat in Example 9.1 comes from the combustion of propane. What mass of propane must be burned to furnish this amount of energy, assuming the heat transfer process is 60.% efficient?

For the process H2O(l) 88n H2O(g) at 298 K and 1.0 atm, DH is more positive than DE by 2.5 kJ/mol. What does the 2.5 kJ/mol quantity represent

For the following reactions at constant pressure, predict if DH . DE, DH , DE, or DH 5 DE. a. 2HF(g) 88n H2(g) 1 F2(g) b. N2(g) 1 3H2(g) 88n 2NH3(g) c. 4NH3(g) 1 5O2(g) 88n 4NO(g) 1 6H2O(g)

Calculate the energy required to heat 1.00 kg of ethane gas (C2H6) from 25.08C to 75.08C first under conditions of constant volume and then at a constant pressure of 2.00 atm. Calculate DE, DH, and w for these processes also. (See Table 9.1 for relevant data.)

Calculate q, w, DE, and DH for the process in which 88.0 g of nitrous oxide gas (N2O) is cooled from 1658C to 558C at a constant pressure of 5.00 atm. (See Table 9.1.)

Consider 111 J of heat added to 30.3 g of Ne on STP. Determine w, DE, and DH if the heat is transferred at constant volume. Do the same determinations if the heat is transferred at constant pressure. Calculate the final temperature under each condition.

Consider a sample containing 2.00 moles of a monatomic ideal gas that undergoes the following changes: PA 5 10.0 atm 1 PB 5 10.0 atm 2 PC 5 20.0 atm VA 5 10.0 L 88n VB 5 5.0 L 88n VC 5 5.0 L 3 PD 5 20.0 atm 88n VD 5 25.0 L For each step, assume that the external pressure is constant and equals the final pressure of the gas for that step. Calculate q, w, DE, and DH for each step and for the overall change from state A to state D

Explain how calorimetry works to calculate DH or DE for a reaction. Does the temperature of the calorimeter increase or decrease for an endothermic reaction? How about for an exothermic reaction? Explain why DH is obtained directly from a coffee cup calorimeter, whereas DE is obtained directly from a bomb calorimeter.

The specific heat capacity of silver is 0.24 J 8C21 g21. a. Calculate the energy required to raise the temperature of 150.0 g Ag from 273 K to 298 K. b. Calculate the energy required to raise the temperature of 1.0 mole of Ag by 1.08C (called the molar heat capacity of silver). c. It takes 1.25 kJ of energy to heat a sample of pure silver from 12.08C to 15.28C. Calculate the mass of the sample of silver

Consider the substances in Table 9.3. Which substance requires the largest amount of energy to raise the temperature of 25.0 g of the substance from 15.08C to 37.08C? Calculate the energy. Which substance in Table 9.3 has the largest temperature change when 550. g of the substance absorbs 10.7 kJ of energy? Calculate the temperature change.

A 150.0-g sample of a metal at 75.08C is added to 150.0 g of H2O at 15.08C. The temperature of the water rises to 18.38C. Calculate the specific heat capacity of the metal, assuming that all the heat lost by the metal is gained by the water.

A 150.0-g sample of a metal at 75.08C is added to 150.0 g of H2O at 15.08C. The temperature of the water rises to 18.38C. Calculate the specific heat capacity of the metal, assuming that all the heat lost by the metal is gained by the water.

A biology experiment requires the preparation of a water bath at 37.08C (body temperature). The temperature of the cold tap water is 22.08C, and the temperature of the hot tap water is 55.08C. If a student starts with 90.0 g of cold water, what mass of hot water must be added to reach 37.08C?

A 5.00-g sample of aluminum pellets (specific heat capacity 5 0.89 J 8C21 g21) and a 10.00-g sample of iron pellets (specific heat capacity 5 0.45 J 8C21 g21) are heated to 100.08C. The mixture of hot iron and aluminum is then dropped into 97.3 g of water at 22.08C. Calculate the final temperature of the metal and water mixture, assuming no heat loss to the surroundings.

A sample of nickel is heated to 99.88C and placed in a coffee cup calorimeter containing 150.0 g water at 23.58C. After the metal cools, the final temperature of metal and water mixture is 25.08C. If the specific heat capacity of nickel is 0.444 J/8C g, what mass of nickel was originally heated? Assume no heat loss to the surroundings.

Hydrogen gives off 120. J/g of energy when burned in oxygen, and methane gives off 50. J/g under the same circumstances. If a mixture of 5.0 g hydrogen and 10. g methane is burned, and the heat released is transferred to 50.0 g water at 25.08C, what final temperature will be reached by the water?

In a coffee cup calorimeter, 50.0 mL of 0.100 M AgNO3 and 50.0 mL of 0.100 M HCl are mixed. The following reaction occurs: Ag1(aq) 1 Cl2(aq) 88n AgCl(s) If the two solutions are initially at 22.608C, and if the final temperature is 23.408C, calculate DH for the reaction in kJ/mol of AgCl formed. Assume a mass of 100.0 g for the combined solution and a specific heat capacity of 4.18 J 8C21 g21.

In a coffee cup calorimeter, 100.0 mL of 1.0 M NaOH and 100.0 mL of 1.0 M HCl are mixed. Both solutions were originally at 24.68C. After the reaction, the final temperature is 31.38C. Assuming that all the solutions have a density of 1.0 g/cm3 and a specific heat capacity of 4.18 J/g ?, calculate the enthalpy change for the neutralization of HCl by NaOH. Assume that no heat is lost to the surroundings or to the calorimeter.

A coffee cup calorimeter initially contains 125 g water at 24.28C. Potassium bromide (10.5 g), also at 24.28C, is added to the water, and after the KBr dissolves, the final temperature is 21.18C. Calculate the enthalpy change for dissolving the salt in J/g and kJ/mol. Assume that the specific heat capacity of the solution is 4.18 J 8C21 g21 and that no heat is transferred to the surroundings or to the calorimeter

In a coffee cup calorimeter, 1.60 g of NH4NO3 is mixed with 75.0 g of water at an initial temperature of 25.008C. After dissolution of the salt, the final temperature of the calorimeter contents is 23.348C. Assuming the solution has a heat capacity of 4.18 J 8C21 g21 and assuming no heat loss to the calorimeter, calculate the enthalpy change for the dissolution of NH4NO3 in units of kJ/mol.

Consider the dissolution of CaCl2: CaCl2(s) 88n Ca21(aq) 1 2Cl2(aq) DH 5 281.5 kJ An 11.0-g sample of CaCl2 is dissolved in 125 g of water, with both substances at 25.08C. Calculate the final temperature of the solution assuming no heat loss to the surroundings and assuming the solution has a specific heat capacity of 4.18 J 8C21 g21.

Consider the reaction 2HCl(aq) 1 Ba(OH)2(aq) 88n BaCl2(aq) 1 2H2O(l) DH 5 2118 kJ Calculate the heat when 100.0 mL of 0.500 M HCl is mixed with 300.0 mL of 0.100 M Ba(OH)2. Assuming that the temperature of both solutions was initially 25.08C and that the final mixture has a mass of 400.0 g and a specific heat capacity of 4.18 J 8C21 g21, calculate the final temperature of the mixture.

The heat capacity of a bomb calorimeter was determined by burning 6.79 g of methane (energy of combustion 5 2802 kJ/mol CH4) in the bomb. The temperature changed by 10.88C. a. What is the heat capacity of the bomb? b. A 12.6-g sample of acetylene (C2H2) produced a temperature increase of 16.98C in the same calorimeter. What is the energy of combustion of acetylene (in kJ/mol)?

The combustion of 0.1584 g benzoic acid increases the temperature of a bomb calorimeter by 2.548C. Calculate the heat capacity of this calorimeter. (The energy released by combustion of benzoic acid is 26.42 kJ/g.) A 0.2130-g sample of vanillin (C8H8O3) is then burned in the same calorimeter, and the tempearture increases by 3.258C. What is the energy of combustion per gram of vanillin? Per mole of vanillin?

Combustion of table sugar produces CO2(g) and H2O(l). When 1.46 g of table sugar is combusted in a constantvolume (bomb) calorimeter, 24.00 kJ of heat is liberated. a. Assuming that table sugar is pure sucrose [C12H22O11(s)], write the balanced equation for the combustion reaction. b. Calculate DE in kJ/mol C12H22O11 for the combustion reaction of sucrose

Calculate w and DE when 1 mole of a liquid is vaporized at its boiling point (80.8C) and 1.00 atm pressure. DHvap for the liquid is 30.7 kJ mol21 at 80.8C.calculate DH for the reaction (g) ( + g) (g) ( + g) On the basis of enthalpy change, is this a useful reaction for the synthesis of ammonia?

Calculate DH for the reaction 2NH3(g) 1 1 2O2(g) 88n N2H4(l) 1 H2O(l) given the following data: 2NH3(g) 1 3N2O(g) 88n 4N2(g) 1 3H2O(l) DH 5 21010. kJ N2O(g) 1 3H2(g) 88n N2H4(l) 1 H2O(l) DH 5 2317 kJ N2H4(l) 1 O2(g) 88n N2(g) 1 2H2O(l) DH 5 2623 kJ H2(g) 1 1 2O2(g) 88n H2O(l) DH 5 2286 kJ

Given the following data: C2H2(g) 1 5 2O2(g) 88n 2CO2(g) 1 H2O(l) DH 5 21300. kJ C(s) 1 O2(g) 88n CO2(g) DH 5 2394 kJ H2(g) 1 1 2O2(g) 88n H2O(l) DH 5 2286 kJ calculate DH for the reaction 2C(s) 1 H2(g) 88n C2H2(g)

Given the following data: 2ClF(g) 1 O2(g) 88n Cl2O(g) 1 F2O(g) DH 5 167.4 kJ 2ClF3(g) 1 2O2(g) 88n Cl2O(g) 1 3F2O(g) DH 5 341.4 kJ 2F2(g) 1 O2(g) 88n 2F2O(g) DH 5 243.4 kJ calculate DH for the reaction ClF(g) 1 F2(g) 88n ClF3(g)

Given the following data: Ca(s) 1 2C(graphite) 88n CaC2(s) DH 5 262.8 kJ Ca(s) 1 1 2O2(g) 88n CaO(s) DH 5 2635.5 kJ CaO(s) 1 H2O(l) 88n Ca(OH)2(aq) DH 5 2653.1 kJ C2H2(g) 1 5 2O2(g) 88n 2CO2(g) 1 H2O(l) DH 5 21300. kJ C(graphite) 1 O2(g) 88n CO2(g) DH 5 2393.5 kJ calculate DH for the reaction CaC2(s) 1 2H2O(l) 88n Ca(OH)2(aq) 1 C2H2(g)

Given the following data: Fe2O3(s) 1 3CO(g) 88n 2Fe(s) 1 3CO2(g) DH 5 223 kJ 3Fe2O3(s) 1 CO(g) 88n 2Fe3O4(s) 1 CO2(g) DH 5 239 kJ Fe3O4(s) 1 CO(g) 88n 3FeO(s) 1 CO2(g) DH 5 18 kJ calculate DH for the reaction FeO(s) 1 CO(g) 88n Fe(s) 1 CO2(g)

Combustion reactions involve reacting a substance with oxygen. When compounds containing carbon and hydrogen are combusted, carbon dioxide and water are the products. Using the enthalpies of combustion for C4H4 (22341 kJ/mol), C4H8 (22755 kJ/mol), and H2 (2286 kJ/mol), calculate DH for the reaction C4H4(g) 1 2H2(g) 88n C4H8(g)

Given the following data: 2O3(g) 88n 3O2(g) DH 5 2427 kJ O2(g) 88n 2O(g) DH 5 495 kJ NO(g) 1 O3(g) 88n NO2(g) 1 O2(g) DH 5 2199 kJ calculate DH for the reaction NO(g) 1 O(g) 88n NO2(g)

The bombardier beetle uses an explosive discharge as a defensive measure. The chemical reaction involved is the oxidation of hydroquinone by hydrogen peroxide to produce quinone and water: C6H4(OH)2(aq) 1 H2O2(aq) 88n C6H4O2(aq) 1 2H2O(l) Calculate DH for this reaction from the following data: C6H4(OH)2(aq) 88n C6H4O2(aq) 1 H2(g) DH 5 177.4 kJ H2(g) 1 O2(g) 88n H2O2(aq) DH 5 2191.2 kJ H2(g) 1 1 2O2(g) 88n H2O(g) DH 5 2241.8 kJ H2O(g) 88n H2O(l) DH 5 243.8 kJ

Given the definition of the standard enthalpy of formation for a substance, write separate reactions for the formation of NaCl, H2O, C6H12O6, and PbSO4 that have DH8 values equal to DH8f for each compound.

The combustion of methane can be represented as follows: Reactants Step 1 (a) Step 2 (c) Elements Products Ha = 75 kJ (b) Hb = 0 kJ (d) Hd = 572 kJ a. Use this information to determine the value of DH for the combustion of methane to form CO2(g) and 2H2O(l). b. What is DH8f for an element in its standard state? Why is this? Use the figure above to support your answer. c. How does DH for the reaction CO2(g) 1 2H2O(l) 88n CH4(g) 1 O2(g) compare to that of the combustion of methane? Why is this?

Use the values of DH8f in Appendix 4 to calculate DH8 for the following reactions. a. (g) ( + g) ( + g) (g) ( + g) N H O C b. Ca3(PO4)2(s) 1 3H2SO4(l) 88n 3CaSO4(s) 1 2H3PO4(l) c. NH3(g) 1 HCl(g) 88n NH4Cl(s) d. (l) ( + g) (g) ( + g) e. SiCl4(l) 1 2H2O(l) 88n SiO2(s) 1 4HCl(aq) f. MgO(s) 1 H2O(l) 88n Mg(OH)2(s)

The Ostwald process for the commercial production of nitric acid from ammonia and oxygen involves the following steps: 4NH3(g) 1 5O2(g) 88n 4NO(g) 1 6H2O(g) 2NO(g) 1 O2(g) 88n 2NO2(g) 3NO2(g) 1 H2O(l) 88n 2HNO3(aq) 1 NO(g) a. Use the values of DH8f in Appendix 4 to calculate the value of DH8 for each of the preceding reactions. b. Write the overall equation for the production of nitric acid by the Ostwald process by combining the preceding equations. (Water is also a product.) Is the overall reaction exothermic or endothermic?

Calculate DH8 for each of the following reactions using the data in Appendix 4: 4Na(s) 1 O2(g) 88n 2Na2O(s) 2Na(s) 1 2H2O(l) 88n 2NaOH(aq) 1 H2(g) 2Na(s) 1 CO2(g) 88n Na2O(s) 1 CO(g) Explain why a water or carbon dioxide fire extinguisher might not be effective in putting out a sodium fire

The reusable booster rockets of the space shuttle use a mixture of aluminum and ammonium perchlorate as fuel. A possible reaction is 3Al(s) 1 3NH4ClO4(s) 88n Al2O3(s) 1 AlCl3(s) 1 3NO(g) 1 6H2O(g) Calculate DH8 for this reaction.

The space shuttle Orbiter utilizes the oxidation of methylhydrazine by dinitrogen tetroxide for propulsion: 4N2H3CH3 1l2 1 5N2O4 1l2 h 12H2O1g2 1 9N2 1g2 1 4CO2 1g2 Calculate DH8 for this reaction

Does the reaction in Exercise 76 or that in Exercise 77 produce more energy per kilogram of reactant mixture (stoichiometric amounts)?

At 298 K, the standard enthalpies of formation for C2H2(g) and C6H6(l) are 227 kJ/mol and 49 kJ/mol, respectively. a. Calculate DH8 for C6H6(l) 88n 3C2H2(g) b. Both acetylene (C2H2) and benzene (C6H6) can be used as fuels. Which compound would liberate more energy per gram when combusted in air?

occur in the atmosphere. a. C2H4(g) 1 O3(g) n CH3CHO(g) 1 O2(g) b. O3(g) 1 NO(g) n NO2(g) 1 O2(g) c. SO3(g) 1 H2O(l) n H2SO4(aq) d. 2NO(g) 1 O2(g) n 2NO2(g

Use the reaction 2ClF3(g) 1 2NH3(g) 88n N2(g) 1 6HF(g) 1 Cl2(g) DH8 5 21196 kJ to calculate DH8f for ClF3(g).

The standard enthalpy of combustion of ethene gas [C2H4(g)] is 21411.1 kJ/mol at 298 K. Given the following enthalpies of formation, calculate DH8f for C2H4(g). CO2(g) 2393.5 kJ/mol H2O(l) 2285.8 kJ/mol

What is incomplete combustion of fossil fuels? Why can this be a problem?

Explain the advantages and disadvantages of hydrogen as an alternative fuel.

The complete combustion of acetylene [C2H2(g)] produces 1300. kJ of energy per mole of acetylene consumed. How many grams of acetylene must be burned to produce enough heat to raise the temperature of 1.00 gal of water by 10.08C if the process is 80.0% efficient? Assume the density of water is 1.00 g/cm3.

Assume that 4.19 3 106 kJ of energy is needed to heat a home. If this energy is derived from the combustion of methane (CH4), what volume of methane, measured at STP, must be burned? (DH8combustion for CH4 5 2891 kJ/mol)

Syngas can be burned directly or converted to methanol. Calculate DH8 for the reaction CO(g) 1 2H2(g) 88n CH3OH(l)

Ethanol (C2H5OH) has been proposed as an alternative fuel. Calculate the standard enthalpy of combustion per gram of liquid ethanol.

Methanol (CH3OH) has also been proposed as an alternative fuel. Calculate the standard enthalpy of combustion per gram of liquid methanol, and compare this answer to that for ethanol in Exercise 8

Some automobiles and buses have been equipped to burn propane (C3H8) as a fuel. Compare the amount of energy that can be obtained per gram of C3H8(g) with that per gram of gasoline, assuming that gasoline is octane [C8H18(l)]. (See Example 9.8.) Look up the physical properties of propane. What disadvantages are there to using propane instead of gasoline as a fuel?

Consider the following cyclic process carried out in two steps on a gas: Step 1: 45 J of heat is added to the gas, and 10. J of expansion work is performed. Step 2: 60. J of heat is removed from the gas as the gas is compressed back to the initial state. Calculate the work for the gas compression in step 2

Determine DE for the process H2O(l) 88n H2O(g) at 258C and 1 atm

The standard enthalpy of formation of H2O(l) at 298 K is 2285.8 kJ/mol. Calculate the change in internal energy for the following process at 298 K and 1 atm: H2O(l) 88n H2(g) 1 1 2O2(g) DE8 5 ?

A piece of chocolate cake contains about 400 Calories. A nutritional Calorie is equal to 1000 calories (thermochemical calories). How many 8-in-high steps must a 180-lb man climb to expend the 400 Cal from the piece of cake? See Exercise 15 for the formula for potential energy.

It has been determined that the body can generate 5500 kJ of energy during one hour of strenuous exercise. Perspiration is the bodys mechanism for eliminating this heat. What mass of water would have to be evaporated through perspiration to rid the body of the heat generated during 2 hours of exercise? (The heat of vaporization of water is 40.6 kJ/mol.)

Nitromethane, CH3NO2, can be used as a fuel. When the liquid is burned, the (unbalanced) reaction is mainly CH3NO2 1l2 1 O2 1g2 h CO2 1g2 1 N2 1g2 1 H2O1g2 a. The standard enthalpy change of reaction (DH8rxn) for the balanced reaction (with lowest wholenumber coefficients) is 21288.5 kJ. Calculate DHf 8 for nitromethane. b. A 15.0-L flask containing a sample of nitromethane is filled with O2 and the flask is heated to 100.C.At this temperature, and after the reaction is complete, the total pressure of all the gases inside the flask is 950. torr. If the mole fraction of nitrogen (xnitrogen) is 0.134 after the reaction is complete, what mass of nitrogen was produced?

In a bomb calorimeter, the bomb is surrounded by water that must be added for each experiment. Since the amount of water is not constant from experiment to experiment, mass must be measured in each case. The heat capacity of the calorimeter is broken down into two parts: the water and the calorimeter components. If a calorimeter contains 1.00 kg of water and has a total heat capacity of 10.84 kJ/8C, what is the heat capacity of the calorimeter components?

The bomb calorimeter in Exercise 97 is filled with 987 g of water. The initial temperature of the calorimeter contents is 23.328C. A 1.056-g sample of benzoic acid (DEcomb 5 226.42 kJ/g) is combusted in the calorimeter. What is the final temperature of the calorimeter contents?

When 1.00 L of 2.00 M Na2SO4 solution at 30.08C is added to 2.00 L of 0.750 M Ba(NO3)2 solution at 30.08C in a calorimeter, a white solid (BaSO4) forms. The temperature of the mixture increases to 42.08C. Assuming that the specific heat capacity of the solution is 6.37 J 8C21 g21 and that the density of the final solution is 2.00 g/mL, calculate the enthalpy change per mole of BaSO4 formed.

If a student performs an endothermic reaction in a calorimeter, how does the calculated value of DH differ from the actual value if the heat exchanged with the calorimeter is not taken into account?

The enthalpy of neutralization for the reaction of a strong acid with a strong base is 256 kJ/mol of water produced. How much energy will be released when 200.0 mL of 0.400 M HNO3 is mixed with 150.0 mL of 0.500 M KOH?

Three gas-phase reactions were run in a constant-pressure piston apparatus as illustrated. For each reaction, give the balanced reaction and predict the sign of w (the work done) for the reaction. 1 atm S O a. 1 atm 1 atm Cl C O b. 1 atm 1 atm O N 1 atm c. If just the balanced reactions were given, how could you predict the sign of w for a reaction?

Consider the following changes: a. N2(g) n N2(l) b. CO(g) 1 H2O(g) n H2(g) 1 CO2(g) c. Ca3P2(s) 1 6H2O(l) n 3Ca(OH)2(s) 1 2PH3(g) d. 2CH3OH(l) 1 3O2(g) n 2CO2(g) 1 4H2O(l) e. I2(s) n I2(g) At constant temperature and pressure, in which of these changes is work done by the system on the surroundings? By the surroundings on the system? In which of them is no work done?

Nitrogen gas reacts with hydrogen gas to form ammonia gas . Consider the reaction between nitrogen and hydrogen as depicted below: 1 atma. Draw what the container will look like after the reaction has gone to completion. Assume a constant pressure of 1 atm. b. Is the sign of work positive or negative, or is the value of work equal to zero for the reaction? Explain your answer.

Using the following data, calculate the standard heat of formation of ICl(g) in kJ/mol: Cl2(g) 88n 2Cl(g) DH8 5 242.3 kJ I2(g) 88n 2I(g) DH8 5 151.0 kJ ICl(g) 88n I(g) 1 Cl(g) DH8 5 211.3 kJ I2(s) 88n I2(g) DH8 5 62.8 kJ

High-quality audio amplifiers generate large amounts of heat. To dissipate the heat and prevent damage to the electronic devices, manufacturers use heat-radiating metal fins. Would it be better to make these fins out of iron or aluminum? Why? (See Table 9.3 for specific heat capacities.)

Write reactions that correspond to the following enthalpy changes: a. DH8f for solid aluminum oxide b. the standard enthalpy of combustion of liquid ethanol [C2H5OH(l)] c. the standard enthalpy of neutralization of barium hydroxide solution by hydrochloric acid d. DH8f for gaseous vinyl chloride [C2H3Cl(g)] e. the enthalpy of combustion of liquid benzene [C6H6(l)] f. the enthalpy of solution of solid ammonium bromide

Consider a balloon filled with helium at the following conditions. 313 g He 1.00 atm 1910. L Molar Heat Capacity 5 20.8 J 8C21 mol21 The temperature of this balloon is decreased by 41.68C as the volume decreases to 1643 L, with the pressure remaining constant. Determine q, w, and DE (in kJ) for the compression of the balloo

In which of the following systems is(are) work done by the surroundings on the system? Assume pressure and temperature are constant. a. 2SO2 1g2 1 O2 1g2 h 2SO3 1g2 b. CO2 1s2 h CO2 1g2 c. 4NH3 1g2 1 7O2 1g2 h 4NO2 1g2 1 6H2O1g2 d. N2O4 1g2 h 2NO2 1g2 e. CaCO3 1s2 h CaCO1s2 1 CO2 1g

Which of the following processes are exothermic? a. N2 1g2 h 2N1g2 b. H2O1l2 h H2O1s2 c. Cl2 1g2 h 2Cl1g2 d. 2H2 1g2 1 O2 1g2 h 2H2O1g2 e. O2 1g2 h 2O1g2

Consider the reaction B2H6 1g2 1 3O2 1g2 h B2O3 1s2 1 3H2O1g2 DH 5 22035 kJ Calculate the amount of heat released when 54.0 g of diborane is combusted.

A swimming pool, 10.0 m by 4.0 m, is filled with water to a depth of 3.0 m at a temperature of 20.28C. How much energy is required to raise the temperature of the water to 24.68C?

In a coffee-cup calorimeter, 150.0 mL of 0.50 M HCl is added to 50.0 mL of 1.00 M NaOH to make 200.0 g solution at an initial temperature of 48.28C. If the enthalpy of neutralization for the reaction between a strong acid and a strong base is 256 kJ/mol, calculate the final temperature of the calorimeter contents. Assume the specific heat capacity of the solution is 4.184 J 8C21 g21 and assume no heat loss to the surroundings.

Calculate DH for the reaction N2H4 1l2 1 O2 1g2 h N2 1g2 1 2H2O1l2 given the following data: Equation DH (kJ) 2NH3 1g2 1 3N2O1g2 h 4N2 1g2 1 3H2O1l2 21010 N2O1g2 1 3H2 1g2 h N2H4 1l2 1 H2O1l2 2317 2NH3 1g2 1 1 2 O2 1g2 h N2H4 1l2 1 H2O1l2 2143 H2 1g2 1 1 2 O2 1g2 h H2O1l2 2286

Which of the following substances have an enthalpy of formation equal to zero? a. Cl2(g) b. H2(g) c. N2(l) d. Cl(g)

The heat required to raise the temperature from 300.0 K to 400.0 K for 1 mole of a gas at constant volume is 2079 J. The internal energy required to heat the same gas at constant pressure from 550.0 K to 600.0 K is 1305 J. The gas does 150. J of work during this expansion at constant pressure. Is this gas behaving ideally? Is the gas a monatomic gas? Explain.

When water is supercooled, it freezes at a temperature below 0.08C. If 10.9 kJ of heat is released when 2.00 moles of supercooled water at 215.08C freezes, calculate the molar enthalpy of fusion for ice at 0.08C and 1 atm. Assume the molar heat capacities for H2O(s) and H2O(l) are 37.5 J K21 mol21 and 75.3 J K21 mol21, respectively, and are temperature independent.

The sun supplies energy at a rate of about 1.0 kilowatt per square meter of surface area (1 watt 5 1 J/s). The plants in an agricultural field produce the equivalent of 20. kg of sucrose (C12H22O11) per hour per hectare (1 ha 5 10,000 m2). Assuming that sucrose is produced by the reaction 12CO2(g) 1 11H2O(l) 88n C12H22O11(s) 1 12O2(g) DH 5 5640 kJ calculate the percentage of sunlight used to produce the sucrosethat is, determine the efficiency of photosynthesis.

The heat of vaporization of water at the normal boiling point, 373.2 K, is 40.66 kJ/mol. The specific heat capacity of liquid water is 4.184 J K21 g21 and of gaseous water is 2.02 J K21 g21. Assume that these values are independent of temperature. What is the heat of vaporization of water at 298.2 K? Does this result agree with Appendix 4 data?

Consider the following reaction at 2488C and 1.00 atm: CH3Cl(g) 1 H2(g) 88n CH4(g) 1 HCl(g) For this reaction, the enthalpy change at 2488C is 283.3 kJ/mol. At constant pressure the molar heat capacities (Cp) for the compounds are as follows: CH3Cl (48.5 J K21 mol21), H2 (28.9 J K21 mol21), CH4 (41.3 J K21 mol21), and HCl (29.1 J K21 mol21). a. Assuming that the Cp values are independent of temperature, calculate DH8 for this reaction at 258C. b. Calculate DH8f for CH3Cl using data from Appendix 4 and the result from part a.

The best solar panels currently available are about 19% efficient in converting sunlight to electricity. A typical home will use about 40. kWh of electricity per day (1 kWh 5 1 kilowatt hour; 1 kW 5 1000 J/s). Assuming 8.0 hours of useful sunlight per day, calculate the minimum solar panel surface area necessary to provide all of a typical homes electricity. (See Exercise 118 for the energy rate supplied by the sun.)

You have 2.4 moles of a gas contained in a 4.0-L bulb at a temperature of 328C. This bulb is connected to a 20.0-L sealed, initially evacuated bulb via a valve. Assume the temperature remains constant. a. What should happen to the gas when you open the valve? Calculate any changes of conditions. b. Calculate DH, DE, q, and w for the process you described in part a. c. Given your answer to part b, what is the driving force for the process?

An isothermal process is one in which the temperatures of the system and surroundings remain constant at all times. With this in mind, what is wrong with the following statement: For an isothermal expansion of an ideal gas against a constant pressure, DT 5 0, so q 5 0? What is q equal to in an isothermal expansion of an ideal gas against a constant external pressure

You have a 1.00-mole sample of water at 230.8C, and you heat it until you have gaseous water at 140.8C. Calculate q for the entire process. Use the following data: Specific heat capacity of ice 5 2.03 J 8C21 g21 Specific heat capacity of water 5 4.18 J 8C21 g21 Specific heat capacity of steam 5 2.02 J 8C21 g21 H2O(s) 88n H2O(l) DHfusion 5 6.01 kJ/mol (at 08C) H2O(l) 88n H2O(g) DHvaporization 5 40.7 kJ/mol (at 100.8C)

Consider a sample containing 5.00 moles of a monatomic ideal gas that is taken from state A to state B by the following two pathways: Pathway one: PA 5 3.00 atm 1 PC 5 3.00 atm VA 5 15.0 L 88n VC 5 55.0 L 2 PB 5 6.00 atm 88n VB 5 20.0 L Pathway two: PA 5 3.00 atm 3 PD 5 6.00 atm VA 5 15.0 L 88n VD 5 15.0 L 4 PB 5 6.00 atm 88n VB 5 20.0 L For each step, assume that the external pressure is constant and equals the final pressure of the gas for that step. Calculate q, w, DE, and DH for each step, and calculate overall values for each pathway. Explain how the overall values for the two pathways illustrate that DE and DH are state functions, whereas q and w are path functions.

A gaseous hydrocarbon reacts completely with oxygen gas to form carbon dioxide and water vapor. Given the following data, determine DH8f for the hydrocarbon: DHrxn 5 22044.5 kJ/mol DH8f (CO2) 5 2393.5 kJ/mol DH8f (H2O) 5 2242 kJ/mol Density of CO2 and H2O mixture at 1 atm, 200.8C 5 0.751 g/L The density of the hydrocarbon is less than the density of Kr at the same conditions.