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Problems

Author: John Hutchinson

Problem 1 Each possible sequence of the 52 cards in a deck is equally probable. However, when you shuffle a deck and then examine the sequence, the deck is never ordered. Explain why in terms of microstates, macrostates, and entropy.
Problem 2 Assess the validity of the statement, "In all spontaneous processes, the system moves toward a state of lowest energy." Correct any errors you identify.
Problem 3 In each case, determine whether spontaneity is expected at low temperature, high temperature, any temperature, or no temperature: ΔH>0, ΔS>0
ΔH<0, ΔS>0
ΔH>0, ΔS<0
ΔH<0, ΔS<0
Problem 4 Using thermodynamic equilibrium arguments, explain why a substance with weaker intermolecular forces has a greater vapor pressure than one with stronger intermolecular forces.
Problem 5 Why does the entropy of a gas increase as the volume of the gas increases? Why does the entropy decrease as the pressure increases?
Problem 6 For each of the following reactions, calculate the values of ΔS, ΔH, and ΔG at T=298K and use these to predict whether equilibrium will favor products or reactants at T=298K. Also calculate Kp.

2CO(g)+O2(g) 2CO2(g)
O3(g)+NO(g) NO2(g)+O2(g)
2O3(g) 3 O2(g)

Problem 7  Predict the sign of the entropy for the reaction 2H2(g)+O2(g) 2H2O(g) Give an explanation, based on entropy and the Second Law, of why this reaction occurs spontaneously.
Problem 8 For the reaction H2(g) 2H(g), predict the sign of both ΔH and ΔS. Should this reaction be spontaneous at high temperature or at low temperature? Explain.
Problem 9 For each of the reactions in exercise 6, predict whether increases in temperature will shift the reaction equilibrium more towards products or more towards reactants.
Problem 10  Using equation 7 and equation 9, show that for a given set of initial partial pressures where Q is larger than Kp, the reaction will spontaneously create more reactants. Also show that if Q is smaller than Kp, the reaction will spontaneously create more products.




Last Update: 2011-02-16