Total points: 32

General
•	Closed book. You may use a (one page) note sheet, plus a periodic table. 
•	Calculators “required”. 
•	If a question isn’t clear, please ask me about it. 
•	In multi-part questions, if a difficulty with one part is keeping you from going on, please ask about it. 
•	Some questions request a simple answer and an explanation. It’s the explanation that is important. No credit for answer without a requested explanation. 
•	For chemical equations: be sure they are balanced, and show phases for all species. 
•	Show work and show units on all calculations. Use dimensional analysis for all unit conversions. Show correct number of significant figures in final results.

N = 6.02x1023 		R = 0.0821 L·atm/(mol·K)		T(K) = T(C) + 273
Kw, the equilibrium constant for the ionization of water, is 10-14 M2. 

1. (1 pt.; 1/2 pt. per part) In each part, give one example of what is requested; give the chemical formula. 

a. A binary ionic compound that includes sulfur. (A binary compound is one with only two elements.)

b. A binary covalent compound that includes sulfur.

2. (1 pt.) Consider the single replacement reaction of aluminum metal with hydrochloric acid:	
2 Al (s) + 6 HCl (aq)  2 AlCl3 (aq) + 3 H2 (g)

Which atom gains electrons? Write a (balanced) “half reaction” (showing the electron gain) for this part of the reaction.

3. (2 pts.) Consider a bottle that contains 0.100 moles of an ideal gas at -15 C. More gas is added, so that the bottle now contains 0.200 moles of gas. At what temperature would the bottle have the original pressure (i.e., the pressure it had before adding the additional gas)? Explain clearly; show clear work. (Remember, parameters not mentioned are assumed to be constant.)

4. (3 pts.; 1 pt. per part) In parts a and b, calculate the pH of the given solution.

a. [H+] = 10-12 M

b. [OH-] = 10-5 M. Show work.

c. (no credit without explanation) Which (one) of the two solutions above (parts a and b) is more basic? How can you tell?

5. (3 pts.; 1 pt. per part) 
a. Write a balanced equation showing the (“reversible”) acid-base (proton transfer) reaction between phosphoric acid, H3PO4, and the nitrate ion. (As usual, consider only the first proton of the phosphoric acid.)

b. Label each chemical in the equation, above, as to whether it is an acid or a base. Then show the conjugate acid-base pairs.

c. (no credit without explanation) In which direction would this reaction tend to go? How do you know?

6. (2 pts.) You have a 0.135 M solution of iron(II) bromide. How much of this solution do you need to get 8.47 g of solute?

7. (1 pt.; 1/2 pt. per part) Give the oxidation number of the sulfur atom in each of the following chemical species. I encourage you to show how you calculate them (for at least one of them), but will grade these only on the answer. Be sure to include both sign and magnitude.

a. sulfur trioxide, SO3.			b. sulfite ion, SO32-.

8. (3 pts.) You mix solutions of calcium nitrate and sodium fluoride, and observe a precipitate.

a. (1 pt.) Write the complete equation for this reaction. Balance the equation. Show phase for each chemical.

b. (2 pts.) Write the net ionic equation for this reaction. (Balanced, with phases.) Show how you get it.

9. (1 pt.; no credit without explanation) TiCl4 is a liquid at room temperature. Based on that information, is this chemical an ionic or a covalent compound? Explain.

10. (2 pts.) Commercial concentrated sulfuric acid is 18 M. How much of this solution would you need to make 0.20 L of 3.0 M H2SO4? Include proper SF. (Think how many moles do you need? Where will they come from?)

11. (1 pt.) When an ionic compound dissolves in water, it dissociates into the individual ions. For example, we could write the following balanced equation for the dissolution of barium chloride: BaCl2 (s)  Ba2+ (aq) + 2 Cl- (aq)

Write the corresponding balanced equation for the dissolution of sodium sulfate in water.

12. (1 pt.) Sucrose (ordinary table sugar), C12H22O11, is entirely covalent and is neither acidic nor basic. However, it is very soluble in water. (It is very polar, because of all the O atoms.) Somewhat analogously to the previous question, which shows the major species in a solution of a strong electrolyte What are the major species in an aqueous solution of sugar?

13. (4 pts.)  
a. (1 1/2 pts.) Draw two water molecules, using Lewis structures. Show the two molecules hydrogen-bonding to each other. Try to show a reasonable length for the hydrogen bond (relative to the regular bonds). Label the diagram to show why the two molecules are H-bonding to each other.

Parts b and c both depend on part a, but are independent of each other.

b. (1 1/2 pts.) Discuss how many hydrogen bonds one water molecule forms in each of the three physical states of water. Be as quantitative as possible.

c. (1 pt.) What is the shape of a water molecule? Explain, based on the Lewis structure you drew in part a. Use proper shape terminology.

14. (1 pt.) What would be the most polar bond that is possible? (That is, a bond between what two elements would be the most polar bond that is possible?) Explain.

15. (1 pt.; no credit without explanation) You are trying to clean up a stain, and find that water doesn’t help. Which (one) of the following two solvents would you try next: hexane (CH3CH2CH2CH2CH2CH3) or methanol (CH3OH)? Explain, based on the predicted solvent properties of these chemicals. 

16. (1 pt.) A student reports that, for an aqueous solution at 25 C, [H+] = 2x10-4 M and [OH-] = 2x10-4 M. Your comments?

17. (3 pts.; 1 pt. per part) Draw a Lewis structure (electron dot formula) for each of the following

a. a chlorine atom	b. a bromine molecule	c. a fluoride ion (be sure to show the  on the ion)	

18. (1 pt.) The solubility of minerals is an important issue in geochemistry. Compounds that are soluble in water will tend to migrate much more than insoluble compounds. An example of this consideration One reason that long term underground storage of plutonium is considered safe is that the chemical form stored, plutonium(IV) oxide, is very insoluble in water; therefore, even if the storage container is breached, the plutonium will not be very mobile. Emsley gives the solubility of the oxide -- the least soluble oxide known -- as one atom (or presumably, one formula unit of the oxide) per million liters of water. What is this solubility in molarity?

cq\pq3	
(Fall 05)	
12/12/05