Question 2 Indicate whether the following statements are true or false: A. v The entropy of the system increases for all spontaneous reactions. A. False VAn exothermic reaction with negative entropy change can be spontaneous at low temperatures. B. True B. Exothermic reactions with positive entropy changes are spontanecus at all temperatures. Entropy of a perfect crystalline substance at 0 K is zero v The value of AG does not depend on the temperature of the reaction A Moving to another question will save this response. MacBook Air

Question 2 Indicate whether the following statements are true or false: A. v The entropy of the system increases for all spontaneous reactions. A. False VAn exothermic reaction with negative entropy change can be spontaneous at low temperatures. B. True B. Exothermic reactions with positive entropy changes are spontanecus at all temperatures. Entropy of a perfect crystalline substance at 0 K is zero v The value of AG does not depend on the temperature of the reaction A Moving to another question will save this response. MacBook Air

Chemistry

9th Edition

ISBN:9781133611097

Author:Steven S. Zumdahl

Publisher:Steven S. Zumdahl

Chapter17: Spontaneity, Entropy, And Free Energy

Section: Chapter Questions

Problem 4RQ: The free energy change, G, for a process at constant temperature and pressure is related to Suniv...

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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.
For the reaction CH3OH(l)+32O2(g)2H2O(l)+CO2(g) the value of G is 702.2 kJ at 25C. Other data are as follows: Hf (kJ/mol) at 25C S (J/molK) at 25C CH3OH(l) 238.7 126.8 H2O(l) 285.8 70.0 CO2(g) 393.5 213.7 Calculate the standard entropy, S, per mole of O2(g).
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?
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?
In a spontaneous process, S(universe) is (a) 0 (b) = 0 (c) 0
The free energy change, G, for a process at constant temperature and pressure is related to Suniv and reflects the spontaneity of the process. How is G related to Suniv? When is a process spontaneous? Nonspontaneous? At equilibrium? G is a composite term composed of H, T, and S. What is the G equation? Give the four possible sign combinations for H and S. What temperatures are required for each sign combination to yield a spontaneous process? If G is positive, what does it say about the reverse process? How does the G = H TS equation reduce when at the melting-point temperature of a solid-to-liquid phase change or at the boiling-point temperature of a liquid-to-gas phase change? What is the sign of G for the solid-to-liquid phase change at temperatures above the freezing point? What is the sign of G for the liquid-to-gas phase change at temperatures below the boiling point?
Calculate S for the reaction C2H4(g)+3O2(g)2CO2(g)+2H2O(l) See Table 18.1 for values of standard entropies. Does the entropy of the chemical system increase or decrease as you expect? Explain.
There is another free energy state function, the Helmholtz free energy (A), defined as A = E — TS. Comparing this to the definition of G, we see that internal energy has replaced enthalpy in the definition. Under what conditions would this free energy tell us whether or not a process is spontaneous?
Calculate the entropy change for the vaporization of liquid methane and liquid hexane using the following data. Boilling point (1atm) Hvap Methane 112K 8.20 KJ/mol Hexane 342K 28.9 KJ/mol Compare the molar volume of gaseous methane at 112 K with that of gaseous hexane at 342 K. How do the differences in molar volume affect the values of Svap for these liquids?
What is the second law of thermodynamics? For any process, there are four possible sign combinations for Ssys and Ssurr. Which sign combination(s) always give a spontaneous process? Which sign combination(s) always give a non-spontaneous process? Which sign combination(s) may or may not give a spontaneous process?
Limestone is predominantly CaCO3, which can undergo the reaction CaCO3(s)CaO(s)+CO2(g). We know from experience that this reaction is not spontaneous, yet S for the reaction is positive. How can the second law of thermodynamics explain that this reaction is not spontaneous?
The evaporation of one mole of water at 298 K has a standard free allergy change of 8.58 kJ. H2O(l)H2O(g)G298=8.58kJ (a) Is the evaporation of water under standard thermodynamic conditions spontaneous?. (b) Determine the equilibrium constant, KP, for this physical process. (c) By calculating G, determine if the evaporation of water at 298 K is spontaneous when the partial pressure of water, PH2O, is 0.011 atm.. (d) If the evaporation of water were always nonspontaneous at room temperature, wet laundry would never dry when placed outside. In order for laundry to dry, what must be the value of PH2O in the air?