Chapter 28.2, Problem 6P

Consider the following chemical equilibrium: 2SO2(g) + O2(g) = 2SO3(g) • Write the equilibrium constant expression for this reaction. Now compare it to the equilibrium constant expression for the related reaction: • . 1 SO2(g) + O2(g) = SO3(g) 2 How do these two equilibrium expressions differ? What important principle about the dependence of equilibrium constants on the stoichiometry of a reaction can you learn from this comparison?

Given Kp for 2 reactions. Find the Kp for the following reaction: BrCl(g)+ 1/2 I2(g) ->IBr(g) + 1/2 Cl2(g)

For a certain gas-phase reaction at constant pressure, the equilibrium constant Kp is observed to double when the temperature increases from 300 K to 400 K. Calculate the enthalpy change of the reaction, Ah, using this information.

Hydrogen bonding in water plays a key role in its physical properties. Assume that the energy required to break a hydrogen bond is approximately 8 kJ/mol. Consider a simplified two-state model where a "formed" hydrogen bond is in the ground state and a "broken" bond is in the excited state. Using this model: • Calculate the fraction of broken hydrogen bonds at T = 300 K, and also at T = 273 K and T = 373 K. • At what temperature would approximately 50% of the hydrogen bonds be broken? • What does your result imply about the accuracy or limitations of the two-state model in describing hydrogen bonding in water? Finally, applying your understanding: • Would you expect it to be easier or harder to vaporize water at higher temperatures? Why? If you were to hang wet laundry outside, would it dry more quickly on a warm summer day or on a cold winter day, assuming humidity is constant?

(3 pts) Use the Kapustinskii equation to calculate the lattice enthalpy for MgBr2 anddiscuss any differences between this result and that from #4.

(3 pts) Silver metal adopts a fcc unit cell structure and has an atomic radius of 144 pm. Fromthis information, calculate the density of silver. Show all work.

4. (3 pts) From the information below, determine the lattice enthalpy for MgBr2. Show all work. AH/(kJ mol-¹) Sublimation of Mg(s) +148 lonization of Mg(g) +2187 to Mg2+(g) Vaporization of Br₂(1) +31 Dissociation of Br,(g) +193 Electron gain by Br(g) -331 Formation of MgBr₂(s) -524

1. (4 pts-2 pts each part) Consider the crystal structures of NaCl, ZnS, and CsCl (not necessarily shown in this order). a. For one of the three compounds, justify that the unit cell is consistent with stoichiometry of the compound. b. In each of the crystal structures, the cations reside in certain holes in the anions' packing structures. For each compound, what type of holes are occupied by the cations and explain why those particular types of holes are preferred.

(2 pts) What do you expect to happen in a Na2O crystal if a Cl− ion replaces one of the O2−ions in the lattice?