Total points: 25	[Plus bonus problems, 10 pts.]

Take home test. Test 2 covers Ch 6 through Ch 10. Much of the test is on material from the two written assignments. 

DUE: Thursday, 4/7/05, start of class. 

Test is closed book. You may use a note page (one page, 8.5 x 11), plus a periodic table. Calculators “required”. You may supply scratch paper. (You will need some extra paper for the bonus questions.) You may NOT use books, handouts, models, other class or reading notes, other outside sources, etc (except for the specific items listed above).

The general idea is that a take home test is just like a test in class, except that you determine the time and place to take it.

Do not open the test until you are ready to start taking it. Opening the test marks the end of your study time and the beginning of test time. Prior to beginning the test, you may study as much as you wish, and in any way. You may study with others, so long as no one involved has yet opened the test. You may not discuss the test with others (except me) until after the test has been turned in.

This test is similar to other tests in this course (including the samples). Try to resolve doubts about the meaning of test questions by considering them in the context of this course. If you feel there are ambiguities in a question, state any assumptions you make.

Estimated time: 1-2 hours (plus bonus section). It is not a timed test. Take the time you need to do it well. As long as you feel you are being productive, you are welcome to continue. (That also means you need to know when to stop.) I would appreciate it if you would note how long you took.

You should take the test “straight through” in one session (except for the rather long and optional bonus section; see note there). However, you may seek clarification of test questions at a reasonable time after your primary session. This may include asking me about test questions before class.

Feel free to contact me (<contact info provided>), either in preparation for the test or if you need clarification of questions during the test. I will “guarantee” phone availability Wednesday evening 7-9 pm. I will send any test clarifications/corrections that come up to the class e-mail list.

For “emergency use only” You may return the test by mail (postmarked by the due date): <address provided>. (Do NOT send by any method that requires my signature to pick it up.)

•	Please sign the “Honor System pledge” (next page).

Total points: 25	[Plus bonus problems, 10 pts.]

General
•	Closed book. You may use a note page, plus a periodic table. 
•	Calculator “required”.
•	If a question isn’t clear, please ask me 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. 
•	Show phases in all equations.
•	Show work and show units on all calculations. Try to show correct number of significant figures (SF) in final results. I will grade on this in most problems.

N = 6.02x1023; density of water = 1.0 g/mL; 3.785 L = 1 gallon; molar volume of any ideal gas, at STP: 22.4 L. 1 pound = 454 g. Pico = 10-12; nano = 10-9; micro = 10-6.

Please SIGN the following agreement (often referred to as an Honor System pledge).

	I agree to take this test according to the rules established for it.

								(-signature)

Reminder Show phases in all equations you write; use clear dimensional analysis on all conversions; show proper SF in answers.

1. (1 pt.) A major oxide of iodine is diiodine pentoxide. Write the formula for this compound.

2. (2 pts.) Give one example of a combination reaction between a group 1A element and a group 7A element. Write a balanced equation, with phases.

3. (2 pts.) A bottle contains 25 millimoles of hydrogen gas. What is the mass of hydrogen in the bottle? (Careful. What is the formula for the chemical?) Show proper SF.

4. (3 pts.) The final step in making pure platinum (which is used in automobile catalytic converters) is the thermal decomposition of ammonium chloroplatinate, described by the (balanced) equation:

3 (NH4)2PtCl6 (s)  3 Pt (s) + 2 NH4Cl (g) + 2 N2 (g) + 16 HCl (g)

The following two parts are independent.

a. (2 pts.) If you decompose enough ammonium chloroplatinate to make 0.0270 moles of pure platinum, what mass of ammonium chloride will also be produced? Show proper SF.

b. (1 pt.) What is the chloroplatinate ion? Give proper formula, including charge. Briefly explain how you can tell.

5. (2 pts.; 1 pt. per part) The following equation, from a paper in the journal Science, attempts to summarize a complex geological process. (In this equation, the term Corg means carbon that is in organic compounds.)

6.47 SiO2 + 4.8 Al(OH)3 +0.9 Fe(OH)3 + 0.225 Corg + 0.96 K+ + 0.39 Mg2+ + 0.05 Na+ 
+ 0.03 Ti(OH)4 + 1.8 HCO3-  
(K0.96Na0.05)(Al3.27Fe2+0.90Mg0.39Ti0.03)(Si6.47Al1.53)O20(OH)4 + 2.035 CO2 + 7.52 H2O

a. Is the equation balanced for aluminum? Explain. (That is, show how the Al does or does not balance.)

b. If you were going to do quantitative calculations involving this process (such as in #4) Write a conversion factor between moles of iron(III) hydroxide and the gaseous product.

6. (3 pts.) A colleague wanted a salt of chromium(III) that is soluble in water. We checked the stockroom, and found chromium(III) nitrate and chromium(III) oxide.

a. (2 pts.) Write the formulas of these two compounds.

b. (1 pt.; no credit without explanation) Which compound would you choose? Explain how you made the choice.

7. (2 pts.) Calculate the formula mass of potassium phosphate octahydrate. Show the chemical formula you use, and show how you calculate the formula mass. Units? (The phosphate ion is PO43-, which you are supposed to know.)

8. (2 pts.) Methane gas (the stuff you buy from PG&E) burns according to the following balanced equation.

CH4 (g) + 2 O2 (g)  CO2 (g) + 2 H2O (g)

H for this reaction is -802 kJ. 

a. (1 1/2 pts.) How much heat is liberated by burning 112 g of methane gas?

b. (1/2 pt.; no credit without explanation) Judging from the H value, this reaction is (exothermic OR endothermic)? Choose correct term from the parentheses, and briefly explain what it means.

9. (2 pts.) Making high purity materials for computer chips is a continuing challenge. In 1999 scientists at MIT reported a new way to make cadmium selenide, a semi-conductor material under investigation. The method they used is very much like a double replacement reaction, though not in water in this case. They mix solutions in methanol of sodium selenide and cadmium iodide; you can show the phase for these as (methanol) or (MeOH) or just (alc). The desired product does precipitate. Write a balanced equation for this reaction; include phases. (Cadmium ions have charge 2+.)

10. (2 pts.)  It has been estimated that about 1x1014 bacteria live in each human body. What is the total population of bacteria living in humans on earth? Give the answer in moles of bacteria. Show clear work, using dimensional analysis for all steps. State any assumptions you make.

11. (2 pts.; 1/2 pt. per part) Consider an atom with the electron configuration 1s22s22p63s23p2.

a. (No credit without an explanation.) What element has this electron configuration? How can you tell?

b. How many valence electrons does this atom have? 

c. Which electrons are the valence electrons?

d. Give one example of another element with the same number and type of valence electrons.

12. (2 pts.) We have mentioned that limestone is calcium carbonate, CaCO3. It is made when carbon dioxide, dissolved in water, percolates through silicate rocks. Very slowly, the silicate rocks are changed to carbonate rocks. Silicon dioxide is the other product. (Pure silicon dioxide is quartz.) A simple example of a silicate rock would be calcium silicate; the silicate ion is SiO32-. Write a balanced equation, with phases, for the reaction of carbon dioxide with calcium silicate, to produce limestone.

BONUS QUESTIONS: 10 pts. (Reminder The bonus questions are intended as an extra challenge; they are not an important part of your score. Focus on the main set of questions. However, each of the bonus questions deals with some interesting issue, probably a little more advanced than the main coverage in the course. I hope that most of you will at least try most of these.)

This is a rather long bonus section. I did that because I wanted to be able to offer some significant range of more challenging questions, for those who want such a challenge. Because of the length, it is ok if you want to take a break and do this at a second sitting, even the next day. However, except for that, please follow general test procedures here.

•	Please use an extra sheet of paper for these; there is not room to do them on this page.

B1. (1 pt.; 1/2 pt. per part) We have learned about some ions found in ordinary chemistry, but rather unusual ions can occur with intense radiation. Recently, the Cassini spacecraft has found O+ and O2+ in the ring system of Saturn. How many electrons are there in each of these species?
		Total electrons in O+:			Total electrons in O2+:

B2. (2 pts.) How many grams of nitrogen are in 100 g (1.00x102) g of ammonium nitrate? Show clear work.

B3. (4 pts.) A group of students carry out an experiment to determine the formula of zinc iodide. They react 0.76 g of zinc metal with iodine. The product weighs 3.59 g. In each part below, show clear work.

a. (1 pt.) How many moles of zinc did they use? I suggest that you keep an extra SF.

b. (1/2 pt.) What is the mass of iodine in the product?

c. (1 pt.) How many moles of iodine are in the product? (Suggest: calculate this as I, that is, as moles of iodine atoms.)

d. (1 pt.) Based on the experimental data (above), what is the formula of zinc iodide? Explain and/or show how you figure this out.

e. (1/2 pt.) What assumption must you make about the amount of iodine added to the reaction mix?

B4 (3 pts.) Approximately how much carbon dioxide, measured in liters at STP, does your car produce when you drive to class? (If you don’t drive, assume that you did.) You can consider gasoline to be octane, C8H18 (density = 0.7 g/mL).

Emphasize clear logic. It should be clear what you are doing. Make and state assumptions as needed; the numbers are less important than the logic. Use dimensional analysis to guide the calculations.

B5. (1 millipoint) What do the formulas of the following compounds have in common: rubidium bromide, tin(II) sulfide, einsteinium(II) selenide, francium fluoride? (Hint: If you happen to be doing this question at exactly midday, that may help.) (The compounds do not necessarily exist, though they are plausible.)				cq\pq2		3/28/05