Supplemental Instruction 1060 Hixson-Lied Student Success Center 294-6624 www.si.iastate.edu Chapter 19: Entropy and Microstates Supplemental Instruction Iowa State University Leader: Kelsey Course: Chemistry 178 Instructor: Verkade Date: 10/28/2010 1. Demo 10/28/2010 = Lycopodium (Fire Breathing) Pumpkin “Lycopodium powder is a very fine yellow powder made from the spores of Lycopodium clavatum, also known as stag’s horn club moss and running ground pine. Lycopodium powder does not readily burn unless it is dispersed as a mist near flame, where it can ignite because of presence of oxygen to support combustion as well as the increase in available surface area.” Further explanation and how to make a Lycopodium Pumpkin (be careful!) may be found at: http://www.ehow.com/how_6327512_make-lycopodiumpumpkin.html#ixzz13fURJj ZX 2. The second law of thermodynamics states that there is a direction to the way events occur in nature. In any spontaneous process the entropy of the universe increases. Circle the correct answer: a. For a reversible/irreversible process, b. For a reversible/irreversible process, 3. Arrange solid, liquid, and gas in order of decreasing entropy. Explain your choice. 4. (Problem 19.42 in BLBM textbook) Predict the sign of for each of the following processes: a. Gaseous Ar is liquefied at 80 K b. Gaseous N2O4 dissociates to form gaseous NO2 c. Solid potassium reacts with gaseous O2 to form solid potassium superoxide, KO2 d. Lead bromide precipitates upon mixing Pb(NO3)2(aq) and KBr(aq)5. What is a microstate and (Problem 19.29 in BLBM textbook) how would each of the following changes affect the number of microstates available to a system: a. Increase in temperature b. Decrease in volume c. Change of state from liquid to gas 6. Entropy is a measure of how many microstates are associated with a particular macroscopic state. The Boltzmann equation is: . What does each variable stand for? 7. The third law of thermodynamics states that the entropy of a perfect pure crystal at 0 K is zero (state of perfect order). Name the three atomic modes of motion, and what these types of motion do. Illustrate these three kinds of motion with sketches for the HCl
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