What is entropy? Why is entropy important?

Which 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.

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.

Explain why each of the following statements is incorrect. (a) Entropy increases in all spontaneous reactions. (b) Reactions with a negative free energy change (rG 0) are product-favored and occur with rapid transformation of reactants to products. (c) All spontaneous processes are exothermic. (d) Endothermic processes are never spontaneous.

A key component in many chemical engineering designs is the separation of mixtures of chemicals. (a) What happens to the entropy of the system when a chemical mixture is separated? (b) Are designs for chemical separation more likely to rely on spontaneous or nonspontaneous processes?

Suppose you have four identical molecules labeled 1, 2, 3, and 4. Draw 16 simple two-flask diagrams as in thefigure for Question 17, and draw all possible arrangements of the four molecules in the two flasks. How manyof these arrangements have two molecules in each flask?How many have no molecules in one flask? From theseresults, what is the most probable arrangement of molecules? Which arrangement has the highest entropy?

Through photosynthesis, plants build molecules of sugar containing several carbon atoms from carbon dioxide. In the process, entropy is decreased. The reaction of CO2with formic acid to form oxalic acid provides a simple example of a reaction in which the number of carbon atoms in a compound increases: CO2(aq)+HCOOH(aq)H2C2O4(aq) (a) Calculate the standard entropy change for this reaction and discuss the sign of S . (b) How do plants carry out reactions that increase the number of carbon atoms in a sugar, given the changes in entropy for reactions like this?

For each pair of items, tell which has the higher entropy and explain why. (a) Item 1, a sample of solid CO2 at -78°C, or item 2, CO2 vapor at 0°C (b) Item I, solid sugar, or item 2, the same sugar dissolved in a cup of tea (c) Item 1, a 100-mL sample of pure water and a 100-mL sample of pure alcohol, or item 2, the same samples of water and alcohol after they have been poured together and stirred

Compare the compounds in each set below and decide which is expected to have the higher entropy. Assume all are at the same temperature. Check your answers using data in Appendix L. (a) HF(g), HCl(g), or HBr(g) (b) NH4Cl(s) or NH4Cl(aq) (c) C2H4(g) or N2(g) (two substances with the same molar mass) (d) NaCl(s) or NaCl(g)