Hydrogen gas is being considered as a fuel for automobiles.There are many chemical means for producinghydrogen gas from water. One of these reactions is
a. Calculate
b. At what temperature is
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Chapter 18 Solutions
Chemical Principles
- Consider the reaction of 1 mol H2(g) at 25C and 1 atm with 1 mol Br2(l) at the same temperature and pressure to produce gaseous HBr at these conditions. If this reaction is run in a controlled way to generate work, what is the maximum useful work that can be obtained? How much entropy is produced in this case?arrow_forwardConsider the reaction of 2 mol H2(g) at 25C and 1 atm with 1 mol O2(g) at the same temperature and pressure to produce liquid water at these conditions. If this reaction is run in a controlled way to generate work, what is the maximum useful work that can be obtained? How much entropy is produced in this case?arrow_forwardThe decomposition of diamond to graphite [C(diamond) C(graphite)] is thermodynamically favored, but occurs slowly at room temperature. a. Use fG values from Appendix L to calculate rG and Keq for the reaction under standard conditions and 298.15 K. b. Use fH and S values from Appendix L to estimate rG and Keq for the reaction at 1000 K. Assume that enthalpy and entropy values are valid at these temperatures. Does heating shift the equilibrium toward the formation of diamond or graphite? c. Why is the formation of diamond favored at high pressures? d. The phase diagram shows that diamond is thermodynamically favored over graphite at 20,000 atmospheres pressure (about 2 GPa) at room temperature. Why is this conversion actually done at much higher temperatures and pressures?arrow_forward
- What is the third law of thermodynamics? What are standard entropy values, S, and how are these S values (listed in Appendix 4) used to calculate S for a reaction? How would you use Hesss law to calculate S for a reaction? What does the superscript indicate? Predicting the sign of S for a reaction is an important skill to master. For a gas-phase reaction, what do you concentrate on to predict the sign of S? For a phase change, what do you concentrate on to predict the sign of S? That is, how are Ssolid, Sliquid, and Sgas related to one another? When a solute dissolves in water, what is usually the sign of S for this process?arrow_forwardThe combustion of acetylene, C2H2, is a spontaneous reaction given by the equation 2C2H2(g)+5O2(g)4CO2(g)+2H2O(l) As expected for a combustion, the reaction is exothermic. What is the sign of H? What do you expect for the sign of S? Explain the spontaneity of the reaction in terms of the enthalpy and entropy changes.arrow_forwardWhich contains greater entropy, a quantity of frozen benzene or the same quantity of liquid benzene at the same temperature? Explain in terms of the dispersal of energy in the substance.arrow_forward
- Silver carbonate, Ag2CO3, is a light yellow compound that decomposes when heated to give silver oxide and carbon dioxide: Ag2CO3(s)Ag2O(s)+CO2(g) A researcher measured the partial pressure of carbon dioxide over a sample of silver carbonate at 220C and found that it was 1.37 atm. Calculate the partial pressure of carbon dioxide at 25C. The standard enthalpies of formation of silver carbonate and silver oxide at 25C are 505.9 kJ/mol and 31.05 kJ/mol, respectively. Make any reasonable assumptions in your calculations. State the assumptions that you make, and note why you think they are reasonable.arrow_forwardFor the reaction NO(g)+NO2(g)N2O3(g) , use tabulated thermodynamic data to calculate H and S. Then use those values to answer the following questions. (a) Is this reaction spontaneous at 25°C? Explain your answer. (b) If the reaction is not spontaneous at 25°C, will it become spontaneous at higher temperatures or lower temperatures? (c) To show that your prediction is accurate, choose a temperature that corresponds to your prediction in part (b) and calculate G . (Assume that both enthalpy and entropy are independent of temperature.)arrow_forwardWhich of the following are spontaneous processes? a A cube of sugar dissolves in a cup of hot tea. b A rusty crowbar turns shiny. c Butane from a lighter burns in air. d A clock pendulum, initially stopped, begins swinging. e Hydrogen and oxygen gases bubble out from a glass of pure water.arrow_forward
- Identify each of the processes listed as spontaneous or nons-pontaneous. For each nonspontaneous process, describe the corresponding spontaneous process in the opposite direction. (a) A group of cheerleaders builds a human pyramid. (b) Table salt dissolves in water. (c) A cup of cold coffee in a room becomes steaming hot. (d) Water molecules in the air are converted to hydrogen and oxygen gases. (e) A person peels an orange, and you smell it from across the room.arrow_forwardA reaction has H298=100 kj/mol and S298=250 J/mol K. Is the reaction spontaneous at room temperature? If not, under what temperature conditions will it become spontaneous?arrow_forwardIdentify each of the processes listed as spontaneous or non-spontaneous. For each non spontaneous process, describe the corresponding spontaneous process in the opposite direction. (a) Oxygen molecules dissociate to form oxygen atoms. (b) A tray of water is placed in the sun on a warm day and freezes. (c) A solution of salt water forms a layer of acid on top of a layer of base. (d) Silver nitrate is added to a solution of sodium chloride and a precipitate forms. (e) Sulfuric acid sitting in a beaker turns into water by giving off gaseous SO3.arrow_forward
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