The combustion of acetylene, C2H2, is a spontaneous reaction given by the equation
As expected for a combustion, the reaction is exothermic. What is the sign of ΔH°? What do you expect for the sign of ΔS°? Explain the spontaneity of the reaction in terms of the enthalpy and entropy changes.
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Chapter 18 Solutions
Student Solutions Manual for Ebbing/Gammon's General Chemistry
- Solid NH4NO3 is placed in a beaker containing water at 25 C. When the solid has completely dissolved, the temperature of the solution is 23.5 C. (a) Was the process exothermic or endothermic? (b) Was the process spontaneous? (c) Did the entropy of the system increase? (d) Did the entropy of the universe increase?arrow_forwardHow is the sign of q, heat, defined? How does it relate to the total energy of the system?arrow_forwardSome water is placed in a coffee-cup calorimeter. When 1.0 g of an ionic solid is added, the temperature of the solution increases from 21.5C to 24.2C as the solid dissolves. For the dissolving process, what are the signs for Ssys, Ssurr, and Suniv?arrow_forward
- Indicate whether the following processes are spontaneous or nonspontaneous. (a) Liquid water freezing at a temperature below its freezing point (b) Liquid water freezing at a temperature above its freezing point (c) The combustion of gasoline (d) A ball thrown into the air (e) A raindrop falling to the ground (f) Iron rusting in a moist atmospherearrow_forwardThe free energy for a reaction decreases as temperature increases. Explain how this observation is used to determine the sign of either H or S.arrow_forwardGiven the values of H and S, which of the following changes will be spontaneous at constant T and p? a. H = + 25 kJ, S = + 5.0 J/K, T = 300. K b. H = + 25 kJ, S = + 100. J/K, T = 300. K c. H = 10. kJ, S = + 5.0 J/K, T= 298 K d. H = 10.kJ, S =40.J/K, T = 200.Karrow_forward
- What is meant by the standard free-energy change G for a reaction? What is meant by the standard free energy of formation Gf of a substance?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_forwardFor each of the following processes, identify the systemand the surroundings. Identify those processes that arespontaneous. For each spontaneous process, identify theconstraint that has been removed to enable the process to occur: Ammonium nitrate dissolves in water. Hydrogen and oxygen explode in a closed bomb. A rubber band is rapidly extended by a hangingweight. The gas in a chamber is slowly compressed by aweighted piston. A glass shatters on the floor.arrow_forward
- Nickel metal reacts with carbon monoxide to form tetra-carbonyl nickel, Ni(CO)4: Ni(s)+4CO(g)Ni(CO)4(g) This reaction is exploited in the Mond process in order to separate pure nickel from other metals. The reaction above separates nickel from impurities by dissolving it into the gas phase. Conditions are then changed so that the reaction runs in the opposite direction to recover the purified metal. (a) Predict the sign of S for the reaction as written above. (b) Use tabulated thermodynamic data to calculate H, S , and G for the reaction. (c) Find the range of temperatures at which this reaction is spontaneous in the forward direction.arrow_forwardDetermine whether each of the following statements is true or false. (a) An exothermic reaction is spontaneous. (b) When G° is positive, the reaction cannot occur under any conditions. (c) S° is positive for a reaction in which there is an increase in the number of moles. d) If H° and S° are both negative, G° will be negative.arrow_forwardThermodynamics provides a way to interpret everyday occurrences. If you live in northern climates, one common experience is that during early winter, snow falls but then melts when it hits the ground. Both the formation and the melting happen spontaneously. How can thermodynamics explain both of these seemingly opposed events?arrow_forward
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