Use the observations about each chemical reaction in the table below to decide the sign (positive or negative) of the reaction enthalpy AH and reaction entropy as. Note: if you have not been given enough information to decide a sign, select the "unknown" option. reaction observations conclusions ΔΗ is (pick one) This reaction is faster above 53. °C than A below. AS is (pick one) O ΔΗ is (pick one) Crystallization of a pure compound is B spontaneous only below 67. °C. AS is (pick one) O This reaction is spontaneous only above ΔΗ is (pick one) -41. °C but proceeds at a faster rate above - 18. °C. AS is (pick one)

Use the observations about each chemical reaction in the table below to decide the sign (positive or negative) of the reaction enthalpy AH and reaction entropy as. Note: if you have not been given enough information to decide a sign, select the "unknown" option. reaction observations conclusions ΔΗ is (pick one) This reaction is faster above 53. °C than A below. AS is (pick one) O ΔΗ is (pick one) Crystallization of a pure compound is B spontaneous only below 67. °C. AS is (pick one) O This reaction is spontaneous only above ΔΗ is (pick one) -41. °C but proceeds at a faster rate above - 18. °C. AS is (pick one)

Chemistry for Engineering Students

4th Edition

ISBN:9781337398909

Author:Lawrence S. Brown, Tom Holme

Publisher:Lawrence S. Brown, Tom Holme

Chapter10: Entropy And The Second Law Of Thermodynamics

Section: Chapter Questions

Problem 10.91PAE: The reaction shown below is involved in the refining of iron. (The table that follows provides all...

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The reaction CO2(g)+H2(g)CO(g)+H2O(g) is not spontaneous at room temperature but becomes spontaneous at a much higher temperature. What can you conclude from this about the signs of H and S , assuming that the enthalpy and entropy changes are not greatly affected by the temperature change? Explain your reasoning.
Using tabulated thermodynamic data, calculate G for these reactions. (a) Mg3N2(s)+6H2O(l)2NH3(g)+3Mg(OH)2(s) (b) 4CH3NH2(g)+9O2(g)4CO2(g)+10H2O(l)+2N2(g) (c) Fe3O(s)+4CO(g)3Fe(s)+4CO2(g) (d) P4O10(s)+6H2O(l)4H3PO4(aq)
For 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.)
Using tabulated thermodynamic data, calculate G for these reactions. (a) Fe(s)+2HCl(g)FeCl2(s)+H2(g) (b) 3NO2(g)+H2O(l)2HNO3(l)+NO(g) (c) 2K(s)+Cl2(g)2KCl(s) (d) Cl2(g)+2NO(g)2NOCl(g) (e) SiCl4(g)Si(s)+2Cl2(g)
The overall reaction that occurs when sugar is metabolized is C12H22O11(s)+12O2(g)12CO2(g)+11H2O(l) For this reaction, H° is -5650 kJ and G° is -5790 kJ at 25°C. (a) If 25% of the free energy change is actually converted to useful work, how many kilojoules of work are obtained when one gram of sugar is metabolized at body temperature, 37°C? (b) How many grams of sugar would a 120-lb woman have to eat to get the energy to climb the Jungfrau in the Alps, which is 4158 m high? ( w=9.79103mh, where w= work in kilojoules, m is body mass in kilograms, and h is height in meters.)
Use the standard entropy data in Appendix G to determine the change in entropy for each of the reactions listed in Exercise 16.34. All the processes occur at the standard conditions and 25 C.
Consider two processes: sublimation of I2(s) and melting of I2(s) (Note: the latter process can occur at the same temperature but somewhat higher pressure). I2(s)I2(g)I2(s)I2(l) Is S positive or negative in these processes? In which of the processes will the magnitude of the entropy change be greater?
10.104 (a) When a chemical bond forms, what happens to the entropy of the system? (b) Thermodynamically, what allows any bond formation to occur? (c) What do your answers to parts (a) and (b) suggest must be true about the formation of chemical bonds for the octet rule to hold?
10.51 The combustion of acetylene was used in welder's torches for many years because it produces a very hot flame: C2H2(g)+52O2(g)2CO2(g)+H2O(g) H= -1255.5 kJ (a) Use data in Appendix E to calculate S for this reaction, (b) Calculate G and show that the reaction is spontaneous at 25°C. (c) Ls there any temperature range in which this reaction is not spontaneous? (d) Do you think you could use Equation 10.4 to calculate such a temperature range reliably? Explain your answer.
Consider the following reaction at 25C: Cl2(g)2Cl(g)K=1.01037 (a) Calculate G for the reaction at 25C. (b) Calculate G f for Cl(g) at 25C.
Without doing a calculation, predict whether the entropy change will be positive or negative when each of the following reactions occurs in the direction it is written. (a) CH3OH(l)+3/2O2(g)CO2(g)+2H2O(g) (b) Br2(l)+H2(g)2HBr(g) (c) Na(s)+l/2F2(g)NaF(s) (d)CO(g)+2H2(g)CH3OH(l) (e) 2NH3(g)N2(g)+3H2(g)
Using enthalpies of formation (Appendix C), calculate H for the following reaction at 25C. Also calculate S for this reaction from standard entropies at 25C. Use these values to calculate G for the reaction at this temperature. 4HCN(l)+5O2(g)2H2O(g)+4CO(g)+2N2(g)