Calculate K at 298 K for each reaction: (a) MgCO3(s) BA Mg21(aq) 1 CO3 22(aq) (b) H2(g)

Distinguish between the terms spontaneous and instantaneous. Give an example of a process that is spontaneous but very slow, and one that is very fast but not spontaneous.

Distinguish between the terms spontaneous and nonspontaneous. Can a nonspontaneous process occur? Explain.

State the first law of thermodynamics in terms of (a) the energy of the universe; (b) the creation or destruction of energy; (c) the energy change of system and surroundings. Does the first law reveal the direction of spontaneous change? Explain.

State qualitatively the relationship between entropy and freedom of particle motion. Use this idea to explain why you will probably never (a) be suffocated because all the air near you has moved to the other side of the room; (b) see half the water in your cup of tea freeze while the other half boils.

Why is DSvap of a substance always larger than DSfus?

How does the entropy of the surroundings change during an exothermic reaction? An endothermic reaction? Other than the examples in text, describe a spontaneous endothermic process.

(a) What is the entropy of a perfect crystal at 0 K? (b) Does entropy increase or decrease as the temperature rises? (c) Why is DH8 f 5 0 but S8 . 0 for an element? (d) Why does Appendix B list DH8 f values but not DS8 f values?

Which of these processes are spontaneous? (a) Water evaporates from a puddle. (b) A lion chases an antelope. (c) An isotope undergoes radioactive disintegration.

Which of these processes are spontaneous? (a) Earth moves around the Sun. (b) A boulder rolls up a hill. (c) Sodium metal and chlorine gas form solid sodium chloride.

Which of these processes are spontaneous? (a) Methane burns in air. (b) A teaspoonful of sugar dissolves in a cup of hot coffee. (c) A soft-boiled egg becomes raw.

Which of these processes are spontaneous? (a) A satellite falls to Earth. (b) Water decomposes to H2 and O2 at 298 K and 1 atm. (c) Average car prices increase.

Predict the sign of DSsys for each process: (a) A piece of wax melts. (b) Silver chloride precipitates from solution. (c) Dew forms on a lawn in the morning.

Predict the sign of DSsys for each process: (a) Gasoline vapors mix with air in a car engine. (b) Hot air expands. (c) Humidity condenses in cold air.

Predict the sign of DSsys for each process: (a) Alcohol evaporates. (b) A solid explosive converts to a gas. (c) Perfume vapors diffuse through a room.

Predict the sign of DSsys for each process: (a) A pond freezes in winter. (b) Atmospheric CO2 dissolves in the ocean. (c) An apple tree bears fruit.

Without using Appendix B, predict the sign of DS8 for (a) 2K(s) 1 F2(g) - 2KF(s) (b) NH3(g) 1 HBr(g) - NH4Br(s) (c) NaClO3(s) - Na1(aq) 1 ClO3 2(aq)

Without using Appendix B, predict the sign of DS8 for (a) H2S(g) 1 1 2O2(g) - 1 8S8(s) 1 H2O(g) (b) HCl(aq) 1 NaOH(aq) - NaCl(aq) 1 H2O(l) (c) 2NO2(g) - N2O4(g)

Without using Appendix B, predict the sign of DS8 for (a) CaCO3(s) 1 2HCl(aq) - CaCl2(aq) 1 H2O(l) 1 CO2(g) (b) 2NO(g) 1 O2(g) - 2NO2(g) (c) 2KClO3(s) - 2KCl(s) 1 3O2(g)

Without using Appendix B, predict the sign of DS8 for (a) Ag1(aq) 1 Cl2(aq) - AgCl(s) (b) KBr(s) - KBr(aq) (c) H2C CH2 CH3CH CH (g)

Predict the sign of DS for each process: (a) C2H5OH(g) (350 K and 500 torr) - C2H5OH(g) (350 K and 250 torr) (b) N2(g) (298 K and 1 atm) - N2(aq) (298 K and 1 atm) (c) O2(aq) (303 K and 1 atm) - O2(g) (303 K and 1 atm)

Predict the sign of DS for each process: (a) O2(g) (1.0 L at 1 atm) - O2(g) (0.10 L at 10 atm) (b) Cu(s) (3508C and 2.5 atm) - Cu(s) (4508C and 2.5 atm) (c) Cl2(g) (1008C and 1 atm) - Cl2(g) (108C and 1 atm)

Predict which substance has greater molar entropy. Explain. (a) Butane CH3CH2CH2CH3(g) or 2-butene CH3CHCHCH3(g) (b) Ne(g) or Xe(g) (c) CH4(g) or CCl4(l)

Predict which substance has greater molar entropy. Explain. (a) NO2(g) or N2O4(g) (b) CH3OCH3(l) or CH3CH2OH(l) (c) HCl(g) or HBr(g)

Predict which substance has greater molar entropy. Explain. (a) CH3OH(l) or C2H5OH(l) (b) KClO3(s) or KClO3(aq) (c) Na(s) or K(s)

Predict which substance has greater molar entropy. Explain. (a) P4(g) or P2(g) (b) HNO3(aq) or HNO3(l) (c) CuSO4(s) or CuSO4?5H2O(s)

Without consulting Appendix B, arrange each group in order of increasing standard molar entropy (S8). Explain. (a) Graphite, diamond, charcoal (b) Ice, water vapor, liquid water (c) O2, O3, O atoms

Without consulting Appendix B, arrange each group in order of increasing standard molar entropy (S8). Explain. (a) Glucose (C6H12O6), sucrose (C12H22O11), ribose (C5H10O5) (b) CaCO3, Ca 1 C 1 3 2 O2, CaO 1 CO2 (c) SF6(g), SF4(g), S2F10(g)

Without consulting Appendix B, arrange each group in order of decreasing standard molar entropy (S8). Explain. (a) ClO4 2(aq), ClO2 2(aq), ClO3 2(aq) (b) NO2(g), NO(g), N2(g) (c) Fe2O3(s), Al2O3(s), Fe3O4(s)

Without consulting Appendix B, arrange each group in order of decreasing standard molar entropy (S8). Explain. (a) Mg metal, Ca metal, Ba metal (b) Hexane (C6H14), benzene (C6H6), cyclohexane (C6H12) (c) PF2Cl3(g), PF5(g), PF3(g)

For the reaction depicted in the molecular scenes, X is red and Y is green. (a) Write a balanced equation. (b) Determine the sign of DSrxn. (c) Which species has the highest molar entropy?

Describe the equilibrium condition in terms of the entropy changes of a system and its surroundings. What does this description mean about the entropy change of the universe?

For the reaction H2O(g) 1 Cl2O(g) - 2HClO(g), you know DS8 rxn and S8 of HClO(g) and of H2O(g). Write an expression that can be used to determine S8 of Cl2O(g).

For each reaction, predict the sign and find the value of DS8 rxn: (a) 3NO(g) - N2O(g) 1 NO2(g) (b) 3H2(g) 1 Fe2O3(s) - 2Fe(s) 1 3H2O(g) (c) P4(s) 1 5O2(g) - P4O10(s)

For each reaction, predict the sign and find the value of DS8 rxn: (a) 3NO2(g) 1 H2O(l) - 2HNO3(l) 1 NO(g) (b) N2(g) 1 3F2(g) - 2NF3(g) (c) C6H12O6(s) 1 6O2(g) - 6CO2(g) 1 6H2O(g)

Find DS8 rxn for the combustion of ethane (C2H6) to carbon dioxide and gaseous water. Is the sign of DS8 rxn as expected? 20.36 Find DS8 rxn for the combustion of methane to carbon dioxide and liquid water. Is the sign of DS8 rxn as expected?

Find DS8 rxn for the reaction of nitrogen monoxide with hydrogen to form ammonia and water vapor. Is the sign of DS8 rxn as expected?

Find DS8 rxn for the combustion of ammonia to nitrogen dioxide and water vapor. Is the sign of DS8 rxn as expected?

(a) Find DS8 rxn for the formation of Cu2O(s) from its elements.

(a) Find DS8 rxn for the formation of Cu2O(s) from its elements. (b) Calculate DSuniv, and state whether the reaction is spontaneous at 298 K.

(a) Find DS8 rxn for the formation of HI(g) from its elements. (b) Calculate DSuniv, and state whether the reaction is spontaneous at 298 K.

(a) Find DS8 rxn for the formation of CH3OH(l) from its elements. (b) Calculate DSuniv, and state whether the reaction is spontaneous at 298 K.

(a) Find DS8 rxn for the formation of N2O(g) from its elements. (b) Calculate DSuniv, and state whether the reaction is spontaneous at 298 K.

Sulfur dioxide is released in the combustion of coal. Scrubbers use aqueous slurries of calcium hydroxide to remove the SO2 from flue gases. Write a balanced equation for this reaction and calculate DS8 rxn at 298 K [S8 of CaSO3(s) 5 101.4 J/mol?K].

Oxyacetylene welding is used to repair metal structures, including bridges, buildings, and even the Statue of Liberty. Calculate DS8 rxn for the combustion of 1 mol of acetylene (C2H2).

What is the advantage of calculating free energy changes rather than entropy changes to determine reaction spontaneity?

Given that DGsys 5 2TDSuniv, explain how the sign of DGsys correlates with reaction spontaneity.

(a) Is an endothermic reaction more likely to be spontaneous at higher temperatures or lower temperatures? Explain. (b) The change depicted below occurs at constant pressure. Explain your answers to each of the following: (1) What is the sign of DHsys? (2) What is the sign of DSsys? (3) What is the sign of DSsurr? (4) How does the sign of DGsys vary with temperature?

Explain your answers to each of the following for the change depicted below. (a) What is the sign of DHsys? (b) What is the sign of DSsys? (c) What is the sign of DSsurr? (d) How does the sign of DGsys vary with temperature?

With its components in their standard states, a certain reaction is spontaneous only at high T. What do you know about the signs of DH8 and DS8? Describe a process for which this is true. 20.50 How can DS8 be relatively independent of T if S8 of each reactant and product increases with T?

How can DS8 be relatively independent of T if S8 of each reactant and product increases with T?

Calculate DG8 for each reaction using DG8 f values: (a) 2Mg(s) 1 O2(g) - 2MgO(s) (b) 2CH3OH(g) 1 3O2(g) - 2CO2(g) 1 4H2O(g) (c) BaO(s) 1 CO2(g) - BaCO3(s)

Calculate DG8 for each reaction using DG8 f values: (a) H2(g) 1 I2(s) - 2HI(g) (b) MnO2(s) 1 2CO(g) - Mn(s) 1 2CO2(g) (c) NH4Cl(s) - NH3(g) 1 HCl(g)

Find DG8 for the reactions in Problem 20.51 using DH8 f and S8 values.

Find DG8 for the reactions in Problem 20.52 using DH8 f and S8 values.

Consider the oxidation of carbon monoxide: CO(g) 1 1 2O2(g) - CO2(g) (a) Predict the signs of DS8 and DH8. Explain. (b) Calculate DG8 by two different methods.

Consider the combustion of butane gas: C4H10(g) 1 13 2 O2(g) - 4CO2(g) 1 5H2O(g) (a) Predict the signs of DS8 and DH8. Explain. (b) Calculate DG8 by two different methods.

For the gaseous reaction of xenon and fluorine to form xenon hexafluoride: (a) Calculate DS8 at 298 K (DH8 5 2402 kJ/mol and DG8 5 2280. kJ/mol). (b) Assuming that DS8 and DH8 change little with temperature, calculate DG8 at 500. K.

For the gaseous reaction of carbon monoxide and chlorine to form phosgene (COCl2): (a) Calculate DS8 at 298 K (DH8 5 2220. kJ/mol and DG8 5 2206 kJ/mol). (b) Assuming that DS8 and DH8 change little with temperature, calculate DG8 at 450. K.

One reaction used to produce small quantities of pure H2 is CH3OH(g) BA CO(g) 1 2H2(g) (a) Determine DH8 and DS8 for the reaction at 298 K. (b) Assuming that these values are relatively independent of temperature, calculate DG8 at 288C, 1288C, and 2288C. (c) What is the significance of the different values of DG8? (d) At what temperature (in K) does the reaction become spontaneous?

A reaction that occurs in the internal combustion engine is N2(g) 1 O2(g) BA 2NO(g) (a) Determine DH8 and DS8 for the reaction at 298 K. (b) Assuming that these values are relatively independent of temperature, calculate DG8 at 100.8C, 2560.8C, and 3540.8C. (c) What is the significance of the different values of DG8? (d) At what temperature (in K) does the reaction become spontaneous?

As a fuel, H2(g) produces only nonpolluting H2O(g) when it burns. Moreover, it combines with O2(g) in a fuel cell (Chapter 21) to provide electrical energy. (a) Calculate DH8, DS8, and DG8 per mole of H2 at 298 K. (b) Is the spontaneity of this reaction dependent on T? Explain. (c) At what temperature does the reaction become spontaneous?

The U.S. government requires automobile fuels to contain a renewable component. Fermentation of glucose from corn yields ethanol, which is added to gasoline to fulfill this requirement: C6H12O6(s) - 2C2H5OH(l) 1 2CO2(g) Calculate DH8, DS8, and DG8 for the reaction at 258C. Is the spontaneity of this reaction dependent on T? Explain.

(a) If K ,, 1 for a reaction, what do you know about the sign and magnitude of DG8? (b) If DG8 ,, 0 for a reaction, what do you know about the magnitude of K? Of Q?

How is the free energy change of a process related to the work that can be obtained from the process? Is this quantity of work obtainable in practice? Explain.

The scenes and the graph relate to the reaction of X2(g) (black) with Y2(g) (orange) to form XY(g). (a) If reactants and products are in their standard states, what quantity is represented on the graph by x? (b) Which scene represents point 1? Explain. (c) Which scene represents point 2? Explain. Gsys x Extent X2 + Y2 XY

What is the difference between ?G° and ?G? Under what circumstances does ?G = ?G°?

Calculate K at 298 K for each reaction: (a) MgCO3(s) BA Mg21(aq) 1 CO3 22(aq) (b) H2(g) 1 O2(g) BA H2O2(l)

Calculate DG8 at 298 K for each reaction: (a) 2H2S(g) 1 3O2(g) BA 2H2O(g) 1 2SO2(g); K 5 6.57310173 (b) H2SO4(l) BA H2O(l) 1 SO3(g); K 5 4.46310215

Calculate K at 298 K for each reaction: (a) HCN(aq) 1 NaOH(aq) BA NaCN(aq) 1 H2O(l) (b) SrSO4(s) BA Sr21(aq) 1 SO4 22(aq)

Calculate DG8 at 298 K for each reaction: (a) 2NO(g) 1 Cl2(g) BA 2NOCl(g); K 5 1.583107 (b) Cu2S(s) 1 O2(g) BA 2Cu(s) 1 SO2(g); K 5 3.2531037

Use DH8 and DS8 values for the following process at 1 atm to find the normal boiling point of Br2: Br2(l) BA Br2(g)

Use DH8 and DS8 values to find the temperature at which these sulfur allotropes reach equilibrium at 1 atm: S(rhombic) BA S(monoclinic)

Use Appendix B to determine the Ksp of Ag2S.

Use Appendix B to determine the Ksp of CaF2.

For the reaction I2(g) 1 Cl2(g) BA 2ICl(g), calculate Kp at 258C [DG8 f of ICl(g) 5 26.075 kJ/mol].

For the reaction CaCO3(s) BA CaO(s) 1 CO2(g), calculate the equilibrium PCO2 at 258C.

The Ksp of PbCl2 is 1.731025 at 258C. What is DG8? Is it possible to prepare a solution that contains Pb21(aq) and Cl2(aq), at their standard-state concentrations?

The Ksp of ZnF2 is 3.031022 at 258C. What is DG8? Is it possible to prepare a solution that contains Zn21(aq) and F2(aq) at their standard-state concentrations?

The equilibrium constant for the reaction 2Fe31(aq) 1 Hg2 21(aq) BA 2Fe21(aq) 1 2Hg21(aq) is Kc 5 9.131026 at 298 K. (a) What is DG8 at this temperature? (b) If standard-state concentrations of the reactants and products are mixed, in which direction does the reaction proceed? (c) Calculate DG when [Fe31] 5 0.20 M, [Hg2 21] 5 0.010 M, [Fe21] 5 0.010 M, and [Hg21] 5 0.025 M. In which direction will the reaction proceed to achieve equilibrium?

The formation constant for the reaction Ni21(aq) 1 6NH3(aq) BA Ni(NH3)6 21(aq) is Kf 5 5.63108 at 258C. (a) What is DG8 at this temperature? (b) If standard-state concentrations of the reactants and products are mixed, in which direction does the reaction proceed? (c) Determine DG when [Ni(NH3)6 21] 5 0.010 M, [Ni21] 5 0.0010 M, and [NH3] 5 0.0050 M. In which direction will the reaction proceed to achieve equilibrium?

The scenes below depict three gaseous mixtures in which A is reacting with itself to form A2. Assume that each particle represents 0.10 mol and the volume is 0.10 L. 1 2 3 (a) If K 5 0.33, which mixture is at equilibrium? (b) Rank the mixtures from the most positive DG to the most negative DG.

The scenes below depict three gaseous mixtures in which X (orange) and Y2 (black) are reacting to form XY and Y. Assume that each gas has a partial pressure of 0.10 atm. 1 2 3 (a) If K 5 4.5, which mixture is at equilibrium? (b) Rank the mixtures from the most positive DG to the most negative DG.

High levels of ozone (O3) cause rubber to deteriorate, green plants to turn brown, and many people to have difficulty breathing. (a) Is the formation of O3 from O2 favored at all T, no T, high T, or low T? (b) Calculate DG8 for this reaction at 298 K. (c) Calculate DG at 298 K for this reaction in urban smog where [O2] 5 0.21 atm and [O3] 5 531027 atm.

A BaSO4 slurry is ingested before the gastrointestinal tract is x-rayed because it is opaque to x-rays and defines the contours of the tract. Ba21 ion is toxic, but the compound is nearly insoluble. If DG8 at 378C (body temperature) is 59.1 kJ/mol for the process BaSO4(s) BA Ba21(aq) 1 SO4 22(aq) what is [Ba21] in the intestinal tract? (Assume that the only source of SO4 22 is the ingested slurry.)

According to advertisements, a diamond is forever. (a) Calculate DH8, DS8, and DG8 at 298 K for the phase change Diamond - graphite (b) Given the conditions under which diamond jewelry is normally kept, argue for and against the statement in the ad. (c) Given the answers in part (a), what would need to be done to make synthetic diamonds from graphite? (d) Assuming DH8 and DS8 do not change with temperature, can graphite be converted to diamond spontaneously at 1 atm?

Replace each question mark with the correct information: DSrxn DHrxn DGrxn Comment (a) 1 2 2 ? (b) ? 0 2 Spontaneous (c) 2 1 ? Not spontaneous (d) 0 ? 2 Spontaneous (e) ? 0 1 ? (f) 1 1 ? TDS . DH

Among the many complex ions of cobalt are the following: Co(NH3)6 31(aq) 1 3en(aq) BA Co(en)3 31(aq) 1 6NH3(aq) where en stands for ethylenediamine, H2NCH2CH2NH2. Six Co-N bonds are broken and six Co-N bonds are formed in this reaction, so DH8 rxn < 0; yet K . 1. What are the signs of DS8 and DG8? What drives the reaction?

What is the change in entropy when 0.200 mol of potassium freezes at 63.78C (DHfus 5 2.39 kJ/mol)?

Is each statement true or false? If false, correct it. (a) All spontaneous reactions occur quickly. (b) The reverse of a spontaneous reaction is nonspontaneous. (c) All spontaneous processes release heat. (d) The boiling of water at 1008C and 1 atm is spontaneous. (e) If a process increases the freedom of motion of the particles of a system, the entropy of the system decreases. (f) The energy of the universe is constant; the entropy of the universe decreases toward a minimum. (g) All systems disperse their energy spontaneously. (h) Both DSsys and DSsurr equal zero at equilibrium.

Hemoglobin carries O2 from the lungs to tissue cells, where the O2 is released. The protein is represented as Hb in its unoxygenated form and as Hb?O2 in its oxygenated form. One reason CO is toxic is that it competes with O2 in binding to Hb: Hb?O2(aq) 1 CO(g) BA Hb?CO(aq) 1 O2(g) (a) If DG8 < 214 kJ at 378C (body temperature), what is the ratio of [Hb?CO] to [Hb?O2] at 378C with [O2] 5 [CO]? (b) How is Le Chteliers principle used to treat CO poisoning?

Magnesia (MgO) is used for fire brick, crucibles, and furnace linings because of its high melting point. It is produced by decomposing magnesite (MgCO3) at around 12008C. (a) Write a balanced equation for magnesite decomposition. (b) Use DH8 and S8 values to find DG8 at 298 K. (c) Assuming that DH8 and S8 do not change with temperature, find the minimum temperature at which the reaction is spontaneous. (d) Calculate the equilibrium PCO2 above MgCO3 at 298 K. (e) Calculate the equilibrium PCO2 above MgCO3 at 1200 K.

To prepare nuclear fuel, U3O8 (yellow cake) is converted to UO2(NO3)2, which is then converted to UO3 and finally UO2. The fuel is enriched (the proportion of the 235U is increased) by a two-step conversion of UO2 into UF6, a volatile solid, followed by a gaseous-diffusion separation of the 235U and 238U isotopes: UO2(s) 1 4HF(g) - UF4(s) 1 2H2O(g) UF4(s) 1 F2(g) - UF6(s) Calculate DG8 for the overall process at 858C: DH8 f (kJ/mol) S8 (J/mol?K) DG8 f (kJ/mol) UO2(s) 21085 77.0 21032 UF4(s) 21921 152 21830. UF6(s) 22197 225 22068

Methanol, a major industrial feedstock, is made by several catalyzed reactions, such as CO(g) 1 2H2(g) - CH3OH(l). (a) Show that this reaction is thermodynamically feasible. (b) Is it favored at low or at high temperatures? (c) One concern about using CH3OH as an auto fuel is its oxidation in air to yield formaldehyde, CH2O(g), which poses a health hazard. Calculate DG8 at 100.8C for this oxidation.

(a) Write a balanced equation for the gaseous reaction between N2O5 and F2 to form NF3 and O2. (b) Determine DG8 rxn. (c) Find DGrxn at 298 K if PN2O5 5 PF2 5 0.20 atm, PNF3 5 0.25 atm, and PO2 5 0.50 atm.

Consider the following reaction: 2NOBr(g) BA 2NO(g) 1 Br2(g) K 5 0.42 at 373 K Given that S8 of NOBr(g) 5 272.6 J/mol?K and that DS8 rxn and DH8 rxn are constant with temperature, find (a) DS8 rxn at 298 K (b) DG8 rxn at 373 K (c) DH8 rxn at 373 K (d) DH8 f of NOBr at 298 K (e) DG8 rxn at 298 K (f) DG8 f of NOBr at 298 K

Hydrogenation is the addition of H2 to double (or triple) carbon-carbon bonds. Peanut butter and most commercial baked goods include hydrogenated oils. Find DH8, DS8, and DG8 for the hydrogenation of ethene (C2H4) to ethane (C2H6) at 258C.

Styrene is produced by catalytic dehydrogenation of ethylbenzene at high temperature in the presence of superheated steam. (a) Find DH8 rxn, DG8 rxn, and DS8 rxn, given these data at 298 K: DH8 f DG8 f S8 Compound (kJ/mol) (kJ/mol) (J/mol?K) Ethylbenzene, C6H5-CH2CH3 212.5 119.7 255 Styrene, C6H5-CHNCH2 103.8 202.5 238 (b) At what temperature is the reaction spontaneous? (c) What are DG8 rxn and K at 600.8C? (d) With 5.0 parts steam to 1.0 part ethylbenzene in the reactant mixture and the total pressure kept constant at 1.3 atm, what is DG at 50.% conversion, that is, when 50.% of the ethylbenzene has reacted?

Propylene (propene; CH3CHCH2) is used to produce polypropylene and many other chemicals. Although most is obtained from the cracking of petroleum, about 2% is produced by catalytic dehydrogenation of propane (CH3CH2CH3): CH3CH2CH3 --- Pt/Al2O3 CH3CH w CH2 1 H2 Because this reaction is endothermic, heaters are placed between the reactor vessels to maintain the required temperature. (a) If the molar entropy, S8, of propylene is 267.1 J/mol?K, find its entropy of formation, S8 f . (b) Find DG8 f of propylene (DH8 f for propylene 5 20.4 kJ/mol). (c) Calculate DH8 rxn and DG8 rxn for the dehydrogenation. (d) What is the theoretical yield of propylene at 5808C if the initial pressure of propane is 1.00 atm? (e) Would the yield change if the reactor walls were permeable to H2? Explain. (f) At what temperature is the dehydrogenation spontaneous, with all substances in the standard state? Note: Problems 20.99 and 20.100 relate to the thermodynamics of adenosine triphosphate (ATP). Refer to the Chemical Connections essay on pp. 902903.

Find K for (a) the hydrolysis of ATP, (b) the dehydrationcondensation to form glucose phosphate, and (c) the coupled reaction between ATP and glucose. (d) How does each K change when T changes from 258C to 378C?

Energy from ATP hydrolysis drives many nonspontaneous cell reactions: ATP42(aq) 1 H2O(l) BA ADP32(aq) 1 HPO4 22(aq) 1 H1(aq) DG89 5 230.5 kJ Energy for the reverse process comes ultimately from glucose metabolism: C6H12O6(s) 1 6O2(g) - 6CO2(g) 1 6H2O(l) (a) Find K for the hydrolysis of ATP at 378C. (b) Find DG89rxn for metabolism of 1 mol of glucose. (c) How many moles of ATP can be produced by metabolism of 1 mol of glucose? (d) If 36 mol of ATP is formed, what is the actual yield?

From the following reaction and data, find (a) S8 of SOCl2 and (b) T at which the reaction becomes nonspontaneous: SO3(g) 1 SCl2(l) - SOCl2(l) 1 SO2(g) DG8 rxn 5 275.2 kJ SO3(g) SCl2(l) SOCl2(l) SO2(g) DH8 f (kJ/mol) 2396 250.0 2245.6 2296.8 S8 (J/mol?K) 256.7 184 248.1

Write equations for the oxidation of Fe and of Al. Use DG8 f to determine whether either process is spontaneous at 258C.

The molecular scene depicts a gaseous equilibrium mixture at 4608C for the reaction of H2 (blue) and I2 (purple) to form HI. Each molecule represents 0.010 mol and the container volume is 1.0 L. (a) Is Kc ., 5, or , 1? (b) Is Kp ., 5, or , Kc? (c) Calculate DG8 rxn. (d) How would the value of DG8 rxn change if the purple molecules represented H2 and the blue I2? Explain.

A key step in the metabolism of glucose for energy is the isomerization of glucose-6-phosphate (G6P) to fructose- 6-phosphate (F6P): G6P BA F6P; K 5 0.510 at 298 K. (a) Calculate DG8 at 298 K. (b) Calculate DG when Q, the [F6P]/[G6P] ratio, equals 10.0. (c) Calculate DG when Q 5 0.100. (d) Calculate Q if DG 5 22.50 kJ/mol.

A chemical reaction, such as HI forming from its elements, can reach equilibrium at many temperatures. In contrast, a phase change, such as ice melting, is in equilibrium at a given pressure and temperature. Each of the graphs below depicts Gsys vs. extent of change. (a) Which graph depicts how Gsys changes for the formation of HI? Explain. (b) Which graph depicts how Gsys changes as ice melts at 18C and 1 atm? Explain. Extent Extent Extent Extent Gsys A B C D

When heated, the DNA double helix separates into two random coil single strands. When cooled, the random coils reform the double helix: double helix BA 2 random coils. (a) What is the sign of DS for the forward process? Why? (b) Energy must be added to break H bonds and overcome dispersion forces between the strands. What is the sign of DG for the forward process when TDS is smaller than DH? (c) Write an expression for T in terms of DH and DS when the reaction is at equilibrium. (This temperature is called the melting temperature of the nucleic acid.)

In the process of respiration, glucose is oxidized completely. In fermentation, O2 is absent and glucose is broken down to ethanol and CO2. Ethanol is oxidized to CO2 and H2O. (a) Balance the following equations for these processes: Respiration: C6H12O6(s) 1 O2(g) - CO2(g) 1 H2O(l) Fermentation: C6H12O6(s) - C2H5OH(l) 1 CO2(g) Ethanol oxidation: C2H5OH(l) 1 O2(g) - CO2(g) 1 H2O(l) (b) Calculate DG8 rxn for respiration of 1.00 g of glucose. (c) Calculate DG8 rxn for fermentation of 1.00 g of glucose. (d) Calculate DG8 rxn for oxidation of the ethanol from part (c).

Consider the formation of ammonia: N2(g) 1 3H2(g) BA 2NH3(g) (a) Assuming that DH8 and DS8 are constant with temperature, find the temperature at which Kp 5 1.00. (b) Find Kp at 400.8C, a typical temperature for NH3 production. (c) Given the lower Kp at the higher temperature, why are these conditions used industrially?

Kyanite, sillimanite, and andalusite all have the formula Al2SiO5. Each is stable under different conditions (see the graph at right). At the point where the three phases intersect: (a) Which mineral, if any, has the lowest free energy? (b) Which mineral, if any, has the lowest enthalpy? (c) Which mineral, if any, has the highest entropy? (d) Which mineral, if any, has the lowest density? Kyanite Sillimanite Andalusite Temperature Pressure

Acetylene is produced commercially by the partial oxidation of methane. At 15008C and pressures of 110 bar, the yield of acetylene is about 20%. The major side product is carbon monoxide, and some soot and carbon dioxide also form. (a) At what temperature is the desired reaction spontaneous: 2CH4 1 1 2O2 - C2H2 1 2H2 1 H2O (b) Acetylene can also be made by the reaction of its elements, carbon (graphite) and hydrogen. At what temperature is this formation reaction spontaneous? (c) Why must this reaction mixture be immediately cooled?

Synthesis gas, a mixture that includes the fuels CO and H2, is used to produce liquid hydrocarbons and methanol. It is made at pressures up to 100 atm by oxidation of methane followed by the steam re-forming and water-gas shift reactions. Because the process is exothermic, temperatures reach 95011008C, and the conditions are such that the amounts of H2, CO, CO2, CH4, and H2O leaving the reactor are close to the equilibrium amounts for the steam re-forming and water-gas shift reactions: CH4(g) 1 H2O(g) BA CO(g) 1 3H2(g) (steam re-forming) CO(g) 1 H2O(g) BA CO2(g) 1 H2(g) (water-gas shift) (a) At 1000.8C, what are DG8 and DH8 for the steam re-forming reaction and for the water-gas shift reaction? (b) By doubling the steam re-forming step and adding it to the water-gas shift step, we obtain the following combined reaction: 2CH4(g) 1 3H2O(g) BA CO2(g) 1 CO(g) 1 7H2(g) Is this reaction spontaneous at 1000.8C in the standard state? (c) Is it spontaneous at 98 atm and 50.% conversion (when 50.% of the starting materials have reacted)? (d) Is it spontaneous at 98 atm and 90.% conversion?