As a system increases in volume, it absorbs 52.5 J of

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.

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

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

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 in the discussion.

Consider the following statements: Heat is a form of energy, and energy is conserved. The heat lost by a 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. Indicate everything you think is incorrect. Correct the incorrect statements and explain.

Consider 5.5 L of a gas at a pressure of 3.0 atm in a cylinder with a movable piston. The external pressure is changed so that the volume changes to 10.5 L. a. Calculate the work done, and indicate the correct sign. b. Use the preceding data but consider the process to occur in two steps. At the end of the first step, the volume is 7.0 L. The second step results in a final volume of 10.5 L. Calculate the work done, and indicate the correct sign. c. Calculate the work done if after the first step the volume is 8.0 L and the second step leads to a volume of 10.5 L. Does the work differ from that in part b? Explain.

In Question 6 the work calculated for the different conditions in the various parts of the question was different even though the system had the same initial and final conditions. Based on this information, is work a state function? a. Explain how you know that work is not a state function. b. Why does the work increase with an increase in the number of steps? c. Which two-step process resulted in more work, when the first step had the bigger change in volume or when the second step had the bigger change in volume? Explain.

Explain why oceanfront areas generally have smaller temperature fluctuations than inland areas

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

In the equation w PV, why is there a negative sign?

Consider an airplane trip from Chicago, Illinois, to Denver, Colorado. List some path-dependent functions and some state functions for the plane trip.

How is average bond strength related to relative potential energies of the reactants and the products?

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).

What is the difference between H and E?

The enthalpy change for the reaction is 891 kJ for the reaction as written. a. What quantity of heat is released for each mole of water formed? b. What quantity of heat is released for each mole of oxygen reacted?

For the reaction : a. What quantity of heat is required to produce 1 mol of mercury by this reaction? b. What quantity of heat is required to produce 1 mol of oxygen gas by this reaction? c. What quantity of heat would be released in the following reaction as written?

The enthalpy of combustion of CH4(g) when H2O(l) is formed is 891 kJ/mol and the enthalpy of combustion of CH4(g) when H2O(g) is formed is 803 kJ/mol. Use these data and Hesss law to determine the enthalpy of vaporization for water.

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

Standard enthalpies of formation are relative values. What are Hf values relative to?

Why is it a good idea to rinse your thermos bottle with hot water before filling it with hot coffee?

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

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

Calculate the kinetic energy of a baseball (mass 5.25 oz) with a velocity of 1.0  102 mi/h.

Calculate the kinetic energy of an object with a mass of 1.0  105 g and a velocity of 2.0  105 cm/s.

Which has the greater kinetic energy, an object with a mass of 2.0 kg and a velocity of 1.0 m/s or an object with a mass of 1.0 kg and a velocity of 2.0 m/s?

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. What is the kinetic energy and the potential energy of ball B at point II? The potential energy is given by PE mgz, where m is the mass in kilograms, g is the gravitational constant (9.81 m/s2 ), and z is the distance in meters.

A gas absorbs 45 kJ of heat and does 29 kJ of work. Calculate E.

A system releases 125 kJ of heat while 104 kJ of work is done on it. Calculate E

Calculate E for each of the following. a. q 47 kJ, w 88 kJ b. q 82 kJ, w 47 kJ 1047 c. q 47 kJ, w 0 d. In which of these cases do the surroundings do work on the system?

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 E for the overall process.

If the internal energy of a thermodynamic system is increased by 300. J while 75 J of expansion work is done, how much heat was transferred and in which direction, to or from the system?

Calculate the internal energy change for each of the following. a. One hundred (100.) joules of work is 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 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?

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?

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?

A balloon filled with 39.1 mol helium has a volume of 876 L at 0.0C and 1.00 atm pressure. The temperature of the balloon is increased to 38.0C as it expands to a volume of 998 L, the pressure remaining constant. Calculate q, w, and E for the helium in the balloon. (The molar heat capacity for helium gas is .)

One mole of H2O(g) at 1.00 atm and 100.C occupies a volume of 30.6 L. When one mole of H2O(g) is condensed to one mole of H2O(l) at 1.00 atm and 100.C, 40.66 kJ of heat is released. If the density of H2O(l) at this temperature and pressure is 0.996 g/cm3 , calculate E for the condensation of one mole of water at 1.00 atm and 100.C.

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: Why are high temperatures needed to convert N2 and O2 to NO?

The reaction is the last step in the commercial production of sulfuric acid. The enthalpy change for this reaction is 227 kJ. In designing a sulfuric acid plant, is it necessary to provide for heating or cooling of the reaction mixture? Explain.

Are the following processes exothermic or endothermic? a. When solid KBr is dissolved in water, the solution gets colder. b. Natural gas (CH4) is burned in a furnace. c. When concentrated H2SO4 is added to water, the solution gets very hot. d. Water is boiled in a teakettle.

Are the following processes exothermic or endothermic?

The overall reaction in a commercial heat pack can be represented as a. How much heat is released when 4.00 mol iron is reacted with excess O2? b. How much heat is released when 1.00 mol 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 following reaction: a. How much heat is evolved for the production of 1.00 mol 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  108 L at 1.0 atm and 25C. How much heat was evolved when the Hindenburg exploded, assuming all of the hydrogen reacted?

Consider the combustion of propane: Assume that all the heat in Example 6.3 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?

Consider the following reaction: Calculate the enthalpy change for each of the following cases: a. 1.00 g methane is burned in excess oxygen. b. 1.00  103 L methane gas at 740. torr and 25C is burned in excess oxygen

For the process H2O1l2 H2O1g2 at 298 K and 1.0 atm, H is more positive than E by 2.5 kJ/mol. What does the 2.5 kJ/mol quantity represent?

For the following reactions at constant pressure, predict if H E, H E, or H E.

Consider the substances in Table 6.1. Which substance requires the largest amount of energy to raise the temperature of 25.0 g of the substance from 15.0C to 37.0C? Calculate the energy. Which substance in Table 6.1 has the largest temperature change when 550. g of the substance absorbs 10.7 kJ of energy? Calculate the temperature change.

The specific heat capacity of silver is 0.24 J/C g. 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 mol Ag by 1.0C (called the molar heat capacity of silver). c. It takes 1.25 kJ of energy to heat a sample of pure silver from 12.0C to 15.2C. Calculate the mass of the sample of silver.

A 5.00-g sample of one of the substances listed in Table 6.1 was heated from 25.2C to 55.1C, requiring 133 J to do so. What substance was it?

It takes 585 J of energy to raise the temperature of 125.6 g mercury from 20.0C to 53.5C. Calculate the specific heat capacity and the molar heat capacity of mercury.

A 30.0-g sample of water at 280. K is mixed with 50.0 g water at 330. K. Calculate the final temperature of the mixture assuming no heat loss to the surroundings

A sample of nickel is heated to 99.8C and placed in a coffeecup calorimeter containing 150.0 g water at 23.5C. After the metal cools, the final temperature of metal and water mixture is 25.0C. If the specific heat capacity of nickel is 0.444 J/C g, what mass of nickel was originally heated? Assume no heat loss to the surroundings.

A 5.00-g sample of aluminum pellets (specific heat capacity 0.89 J/C g) and a 10.00-g sample of iron pellets (specific heat capacity 0.45 J/C g) are heated to 100.0C. The mixture of hot iron and aluminum is then dropped into 97.3 g water at 22.0C. Calculate the final temperature of the metal and water mixture, assuming no heat loss to the surroundings. 4N

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 25.0C, what final temperature will be reached by the water?

A 150.0-g sample of a metal at 75.0C is added to 150.0 g H2O at 15.0C. The temperature of the water rises to 18.3C. Calculate the specific heat capacity of the metal, assuming that all the heat lost by the metal is gained by the water.

A 110.-g sample of copper (specific heat capacity 0.20 J/C g) is heated to 82.4C and then placed in a container of water at 22.3C. The final temperature of the water and copper is 24.9C. What is the mass of the water in the container, assuming that all the heat lost by the copper is gained 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 to yield the following reaction: The two solutions were initially at 22.60C, and the final temperature is 23.40C. Calculate the heat that accompanies this reaction in kJ/mol of AgCl formed. Assume that the combined solution has a mass of 100.0 g and a specific heat capacity of 4.18 J/C g.

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 24.6C. After the reaction, the final temperature is 31.3C. Assuming that all the solutions have a density of 1.0 g/cm3 and a specific heat capacity of 4.18 J/C 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 24.2C. Potassium bromide (10.5 g), also at 24.2C, is added to the water, and after the KBr dissolves, the final temperature is 21.1C. 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/C g and that no heat is transferred to the surroundings or to the calorimeter.

In a coffee-cup calorimeter, 1.60 g NH4NO3 is mixed with 75.0 g water at an initial temperature of 25.00C. After dissolution of the salt, the final temperature of the calorimeter contents is 23.34C. Assuming the solution has a heat capacity of 4.18 J/C g 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: An 11.0-g sample of CaCl2 is dissolved in 125 g water, with both substances at 25.0C. 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/C g.

Consider the reaction H 118 kJ 2HCl1aq2  Ba1OH221aq2 BaCl21aq2  2H2O1l2. 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 25.0C and that the final mixture has a mass of 400.0 g and a specific heat capacity of 4.18 J/C g, calculate the final temperature of the mixture.

The heat capacity of a bomb calorimeter was determined by burning 6.79 g methane (energy of combustion 802 kJ/mol CH4) in the bomb. The temperature changed by 10.8C. a. What is the heat capacity of the bomb? b. A 12.6-g sample of acetylene, C2H2, produced a temperature increase of 16.9C 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 2.54C. 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 temperature increases by 3.25C. What is the energy of combustion per gram of vanillin? Per mole of vanillin?

The enthalpy of combustion of solid carbon to form carbon dioxide is 393.7 kJ/mol carbon, and the enthalpy of combustion of carbon monoxide to form carbon dioxide is 283.3 kJ/mol CO. Use these data to calculate H for the reaction

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 (2341 kJ/mol), C4H8 (2755 kJ/mol), and H2 (286 kJ/mol), calculate H for the reaction 6

Given the following data calculate H for the reaction On the basis of the enthalpy change, is this a useful reaction for the synthesis of ammonia?

Given the following data calculate H for the reaction

Given the following data NO1g2  O31g2 NO21g2  O21g2 H 199 kJ O21g2 2O1g2 H 495 kJ 2O31g2 3O21g2 H 427 kJ ClF calculate H for the reaction

Calculate H for the reaction given the following data:

Given the following data calculate H for the reaction

Given the following data calculate H for the reaction

Give 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 H values equal to Hf  for each compound

Write reactions for which the enthalpy change will be a. Hf  for solid aluminum oxide. b. The standard enthalpy of combustion of liquid ethanol, C2H5OH(l). c. The standard enthalpy of neutralization of sodium hydroxide solution by hydrochloric acid. d. Hf  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.

Use the values of Hf  in Appendix 4 to calculate H for the following reactions.

Use the values of Hf  in Appendix 4 to calculate H for the following reactions. (See Exercise 77.)

The Ostwald process for the commercial production of nitric acid from ammonia and oxygen involves the following steps: a. Use the values of Hf in Appendix 4 to calculate the value of H 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 H for each of the following reactions using the data in Appendix 4: 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 Calculate H for this reaction.

The space shuttle orbiter utilizes the oxidation of methylhydrazine by dinitrogen tetroxide for propulsion: Calculate H for this reaction

Consider the reaction Calculate Hf  for ClF3(g).

The standard enthalpy of combustion of ethene gas, C2H4(g), is 1411.1 kJ/mol at 298 K. Given the following enthalpies of formation, calculate Hf  for C2H4(g). H2O1l2 285.8 kJ/mol CO21g2 393.5 kJ/mol

Water gas is produced from the reaction of steam with coal: Assuming that coal is pure graphite, calculate H for this reaction.

Syngas can be burned directly or converted to methanol. Calculate H for the reaction

Ethanol (C2H5OH) has been proposed as an alternative fuel. Calculate the standard of 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 87.

Some automobiles and buses have been equipped to burn propane (C3H8). Compare the amounts of energy that can be obtained per gram of C3H8(g) and per gram of gasoline, assuming that gasoline is pure octane, C8H18(l). (See Example 6.11.) Look up the boiling point of propane. What disadvantages are there to using propane instead of gasoline as a fuel?

Acetylene (C2H2) and butane (C4H10) are gaseous fuels with enthalpies of combustion of 49.9 kJ/g and 49.5 kJ/g, respectively. Compare the energy available from the combustion of a given volume of acetylene to the combustion energy from the same volume of butane at the same temperature and pressure.

Assume that 4.19  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? (Hcombustion for CH4 891 kJ/mol)

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 water by 10.0C if the process is 80.0% efficient? Assume the density of water is 1.00 g/cm3 .

The equation for the fermentation of glucose to alcohol and carbon dioxide is The enthalpy change for the reaction is 67 kJ. Is the reaction exothermic or endothermic? Is energy, in the form of heat, absorbed or evolved as the reaction occurs?

One way to lose weight is to exercise! Walking briskly at 4.0 miles per hour for an hour consumes about 400 kcal of energy. How many hours would you have to walk at 4.0 miles per hour to lose one pound of body fat? One gram of body fat is equivalent to 7.7 kcal of energy. There are 454 g in 1 lb.

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 two hours of exercise? (The heat of vaporization of water is 40.6 kJ/mol.)

A biology experiment requires the preparation of a water bath at 37.0C (body temperature). The temperature of the cold tap water is 22.0C, and the temperature of the hot tap water is 55.0C. If a student starts with 90.0 g cold water, what mass of hot water must be added to reach 37.0C?

Quinone is an important type of molecule that is involved in photosynthesis. The transport of electrons mediated by quinone in certain enzymes allows plants to take water, carbon dioxide, and the energy of sunlight to create glucose. A 0.1964-g sample of quinone (C6H4O2) is burned in a bomb calorimeter with a heat capacity of 1.56 kJ/C. The temperature of the calorimeter increases by 3.2C. Calculate the energy of combustion of quinone per gram and per mole.

Combustion of table sugar produces CO2(g) and H2O(l). When 1.46 g table sugar is combusted in a constant-volume (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 E in kJ/mol C12H22O11 for the combustion reaction of sucrose. c. Calculate H in kJ/mol C12H22O11 for the combustion reaction of sucrose at 25C.

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: Calculate H for this reaction from the following data:

Photosynthetic plants use the following reaction to produce glucose, cellulose, and so forth: How might extensive destruction of forests exacerbate the greenhouse effect?

Three gas-phase reactions were run in a constant-pressure piston apparatus as shown in the following illustration. For each reaction, give the balanced reaction and predict the sign of w (the work done) for the reaction.

Consider the following changes: a. b. c. d. e. 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?

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

Calculate H for the reaction A 5.00-g chunk of potassium is dropped into 1.00 kg water at 24.0C. What is the final temperature of the water after the preceding reaction occurs? Assume that all the heat is used to raise the temperature of the water. (Never run this reaction. It is very dangerous; it bursts into flame!)

The enthalpy of neutralization for the reaction of a strong acid with a strong base is 56 kJ/mol water produced. How much energy will be released when 200.0 mL of 0.400 M HCl is mixed with 150.0 mL of 0.500 M NaOH?

When 1.00 L of 2.00 M Na2SO4 solution at 30.0C is added to 2.00 L of 0.750 M Ba(NO3)2 solution at 30.0C in a calorimeter, a white solid (BaSO4) forms. The temperature of the mixture increases to 42.0C. Assuming that the specific heat capacity of the solution is 6.37 J/C g 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 H differ from the actual value if the heat exchanged with the calorimeter is not taken into account?

In a bomb calorimeter, the reaction vessel is surrounded by water that must be added for each experiment. Since the amount of water is not constant from experiment to experiment, the mass of water 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 water and has a total heat capacity of 10.84 kJ/C, what is the heat capacity of the calorimeter components?

The bomb calorimeter in Exercise 108 is filled with 987 g water. The initial temperature of the calorimeter contents is 23.32C. A 1.056-g sample of benzoic acid (Ecomb 26.42 kJ/g) is combusted in the calorimeter. What is the final temperature of the calorimeter contents?

Consider the two space shuttle fuel reactions in Exercises 81 and 82. Which reaction produces more energy per kilogram of reactant mixture (stoichiometric amounts)?

Consider the following equations: Suppose the first equation is reversed and multiplied by , the second and third equations are divided by 2, and the three adjusted equations are added. What is the net reaction and what is the overall heat of this reaction

Given the following data calculate H for the reaction

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 H for C6H61l2 3C2H21g2 b. Both acetylene (C2H2) and benzene (C6H6) can be used as fuels. Which compound would liberate more energy per gram when combusted in air?

Using the following data, calculate the standard heat of formation of ICl(g) in kJ/mol:

Calculate H for each of the following reactions, which occur in the atmosphere

Consider 2.00 mol of an ideal gas that is taken from state A (PA 2.00 atm, VA 10.0 L) to state B (PB 1.00 atm, VB 30.0 L) by two different pathways: These pathways are summarized on the following graph of P versus V: a

Calculate w and E when one mole of a liquid is vaporized at its boiling point (80.C) and 1.00 atm pressure. Hvap for the liquid is 30.7 kJ/mol1 at 80.C.

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

The best solar panels currently available are about 13% efficient in converting sunlight to electricity. A typical home will use about 40. kWh of electricity per day (1 kWh 1 kilowatt hour; 1 kW 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.)

On Easter Sunday, April 3, 1983, nitric acid spilled from a tank car near downtown Denver, Colorado. The spill was neutralized with sodium carbonate: a. Calculate H for this reaction. Approximately 2.0  104 gal nitric acid was spilled. Assume that the acid was an aqueous solution containing 70.0% HNO3 by mass with a density of 1.42 g/cm3 . What mass of sodium carbonate was required for complete neutralization of the spill, and what quantity of heat was evolved? (Hf  for NaNO3(aq) 467 kJ/mol) b. According to The Denver Post for April 4, 1983, authorities feared that dangerous air pollution might occur during the neutralization. Considering the magnitude of H, what was their major concern?

A piece of chocolate cake contains about 400 Calories. A nutritional Calorie is equal to 1000 calories (thermochemical calories), which is equal to 4.184 kJ. How many 8-in-high steps must a 180-lb man climb to expend the 400 Cal from the piece of cake? See Exercise 26 for the formula for potential energy

The standard enthalpy of formation of H2O(l) at 298 K is 285.8 kJ/mol. Calculate the change in internal energy for the following process at 298 K and 1 atm: (Hint: Using the ideal gas equation, derive an expression for work in terms of n, R, and T.)

You have a 1.00-mol sample of water at 30.C and you heat it until you have gaseous water at 140.C. Calculate q for the entire process. Use the following data.

A 500.0-g sample of an element at 195C is dropped into an icewater mixture; 109.5 g ice melts and an icewater mixture remains. Calculate the specific heat of the element. See Exercise 123 for pertinent information.

The preparation of NO2(g) from N2(g) and O2(g) is an endothermic reaction: The enthalpy change of reaction for the balanced equation (with lowest whole-number coefficients) is H 67.7 kJ. If 2.50  102 mL N2(g) at 100.C and 3.50 atm and 4.50  102 mL O2(g) at 100.C and 3.50 atm are mixed, what amount of heat is necessary to synthesize the maximum yield of NO2(g)?

Nitromethane, CH3NO2, can be used as a fuel. When the liquid is burned, the (unbalanced) reaction is mainly a. The standard enthalpy change of reaction (Hrxn) for the balanced reaction (with lowest whole-number coefficients) is 1288.5 kJ. Calculate the Hf 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 ( ) is 0.134 after the reaction is complete, what mass of nitrogen was produced?

A cubic piece of uranium metal (specific heat capacity 0.117 J/C g) at 200.0C is dropped into 1.00 L deuterium oxide (heavy water, specific heat capacity 4.211 J/C g) at 25.5C. The final temperature of the uranium and deuterium oxide mixture is 28.5C. Given the densities of uranium (19.05 g/cm3 ) and deuterium oxide (1.11 g/mL), what is the edge length of the cube of uranium? M

A sample consisting of 22.7 g of a nongaseous, unstable compound X is placed inside a metal cylinder with a radius of 8.00 cm, and a piston is carefully placed on the surface of the compound so that, for all practical purposes, the distance between the bottom of the cylinder and the piston is zero. (A hole in the piston allows trapped air to escape as the piston is placed on the compound; then this hole is plugged so that nothing inside the cylinder can escape.) The piston-and-cylinder apparatus is carefully placed in 10.00 kg water at 25.00C. The barometric pressure is 778 torr. When the compound spontaneously decomposes, the piston moves up, the temperature of the water reaches a maximum of 29.52C, and then it gradually decreases as the water loses heat to the surrounding air. The distance between the piston and the bottom of the cylinder, at the maximum temperature, is 59.8 cm. Chemical analysis shows that the cylinder contains 0.300 mol carbon dioxide, 0.250 mol liquid water, 0.025 mol oxygen gas, and an undetermined amount of a gaseous element A. It is known that the enthalpy change for the decomposition of X, according to the reaction described above, is 1893 kJ/mol X. The standard enthalpies of formation for gaseous carbon dioxide and liquid water are 393.5 kJ/mol and 286 kJ/mol, respectively. The heat capacity for water is 4.184 J/C g. The conversion factor between L atm and J can be determined from the two values for the gas constant R, namely, 0.08206 L atm/K mol and 8.3145 J/K mol. The vapor pressure of water at 29.5C is 31 torr. Assume that the heat capacity of the pistonand-cylinder apparatus is negligible and that the piston has negligible mass. Given the preceding information, determine a. The formula for X. b. The pressurevolume work (in kJ) for the decomposition of the 22.7-g sample of X. c. The molar change in internal energy for the decomposition of X and the approximate standard enthalpy of formation for X. 129. A

A gaseous hydrocarbon reacts completely with oxygen gas to form carbon dioxide and water vapor. Given the following data, determine Hf for the hydrocarbon: Density of CO2 and H2O product mixture at 1.00 atm, 200.C 0.751g/L. The density of the hydrocarbon is less than the density of Kr at the same conditions.