- Principles of Chemistry II: Honors
Spring 2014, Unique 51880
Homework, Week 7
1. How do the equilibrium constants for the following two reactions compare at 25˚C:
Reaction 1: CS2(g) + 3 O2(g) --> CO2(g) + 2 SO2(g)
Reaction 2: 1/3 CS2(g) + O2(g) --> 1/3 CO2(g) + 2/3 SO2(g)
2. Determine the equilibrium constant for reaction 3 (K3) in terms of the equilibrium constants for reactions 1 and 2 (K1 and K2):
Reaction 1: XeF6(g) + H2O(g) --> XeOF4(g) + 2 HF(g)
Reaction 2: XeO4(g) + XeF6(g) --> XeOF4(g) + XeO3F2(g)
Reaction 3: XeO4(g) + 2 HF(g) --> XeO3F2(g) + H2O(g)
3. Phosphorous pentachloride (PCl5) decomposes into phosphorous trichloride (PCl3) and chlorine gas. 1.5 g of PCl5 is placed into a 10 mL sealed vessel and heated to 250˚C, (which is above its sublimation temperature). Determine the partial pressure of all species at equilibrium.
4. Dimethyl ether can be made from the dimerization of methanol:
2 CH3OH(g) --> (CH3)2O(g) + H2O(g)
Describe, both quantitatively and qualitatively, the optimum conditions of pressure and temperature to make as much of this chemical as possible.
5. Determine which of the following molecules is a Bronsted-Lowry acid, and draw its conjugate base.
a) Cl- b) HSO4- c) NH4+
d) NH3 e) H2O f) HCN
6. Niacin (C5H4NCOOH, also called vitamin B3) is an essential nutrient whose deficiency in the diet leads to a nasty disease called pellagra.
a) Write a balanced equation for the equilibrium reaction of niacin with water. This will require determining if the molecule is an acid or a base.
b) Niacin is structurally very similar to pyridine: C5H5N. Would you predict the Ka of niacin to be greater than or less than the Ka of pyridine? Justify your answer.7. The Ka of HIO3 is 0.016 at 25˚C. Determine the pH of an aqueous solution of 0.10 M HIO3.