Which one of the following statements is false O AG7 of elements in their standard states is zero O The entropy of a substance in the liquid phase is lower than the entropy of the same substance in the gas phas O AS for vaporization of a liquid is always positive. O A spontaneous reaction in one direction is always nonspontaneous in the reverse direction. AG should be positive for a spontaneous reaction

At 100C and 1.00 atm, H = 40.6 kJ/mol for the vaporization of water. Estimate G for the vaporization of water at 90.C and 110.C. Assume H and S at 100.C and 1.00 atm do not depend on temperature.

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?

On the basis of your experience, predict which of the following reactions are spontaneous. (a) CO2(s)CO2(g) at 25°C (b) NaCl(s)NaCl(l) at 25°C (c) 2NaCl(s)2Na(s)+Cl2(g) (d) CO2(g)C(s)+O2(g)

Is the following reaction spontaneous as written? Explain. Do whatever calculation is needed to answer the question. CH4(g)+N2(g)HCN(g)+NH3(g)

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).

How does the second law of thermodynamics explain a spontaneous change in a system that becomes more ordered when that process is exothermic?

Calculate the standard entropy change for the reaction CO2(g)+2H2O(l)CH4(g)+2O2(g) . What does the sign of S say about the spontaneity of this reaction?

What happens to the entropy of the universe during a spontaneous process?

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.