1. A: 16 Nov. 2010
Objective: SWBAT calculate percent composition for a compound and determine the percentage of water in a hydrate using laboratory techniques
Do now: Calculate the molar mass of calcium chloride. (Hint: Write the correct formula first!)

2. Agenda
Do now
Percent Composition by Mass: examples and practice problems
Empirical vs. Molecular Formulas
Pre-lab and using a Bunsen burner
Homework: Week 11 Homework #1-8
Read lab handout carefully!

3. Percent Composition by Mass
What is the percent composition of each element in dinitrogen trioxide?
What is the percent composition of each element in magnesium nitrate?
What is the percent composition of each element in glucose (C6H12O6)?

4. a tougher problem…
Calculate the number of grams of nitrogen in 50.0 grams of dinitrogen trioxide.
Calculate the number of grams of magnesium in 10.0 grams of magnesium nitrate
Calculate the mass of carbon in 82.0 g of glucose (C6H12O6)

5. Steps Calculate the molar mass of the compound.
Calculate the percent composition by mass of the element in the problem, but keep it as a decimal, not a percent!
Multiply the percent composition of that element x the mass given in the problem.

6. C: 17 Nov. 2010 Take Out Homework: Week 11 #1-5
Objective: SWBAT differentiate between empirical and molecular formulas and calculate a molecular formula.
Do now: (in your notebook) Calculate the percent composition by mass of each element in silver sulfide. (Hint: Write the correct formula first!)

7. Agenda Do now Homework answers Empirical vs. Molecular Formulas
Calculating a Molecular Formula
Pre-lab and using a Bunsen burner
Homework: Week 11 Homework #6-8

8. A: 18 Nov. 2010 Take out homework: Week 11 #1-5
Objective: SWBAT to write empirical and molecular formulas for a compounds, given laboratory data
Do now: What is the empirical formula of the compound C8H4O12?

9. Agenda Do now Homework solutions Determining molecular formulas
Determining formulas given empirical data
Homework: Week 11 Homework #6-12: Fri.

10. Empirical and Molecular Formulas

11. Molecular Formula Gives a complete list of all the atoms in a molecule
Ex: H2O
2 atoms of H, 1 of O
Ex: C6H12O6
6 atoms of c, 12 of H, 6 of O

12. Empirical Formula
Just gives the lowest, whole number RATIO of elements in the compound
empirical: “by experiment”
Ex: Glucose (Molecular formula: C6H12O6)
Empirical Formula: CH2O
(what is the multiplier?)
Ex: Water (Molecular formula: H2O)
Empirical Formula: H2O

13. What is the empirical formula for each of the following?

14. Finding Molecular formula
Ex 1. What is the molecular formula for a compound with the empirical formula HO and a molar mass of 36 g/mol?
STEP 1 – find the total mass of the empirical formula given to you
STEP 2 – divide the molar mass from the problem by the mass of the empirical formula
STEP 3 – multiply each subscript in the emp. form by the number you just found

15. Examples Ex 2: CH with a molar mass of 39 g/mol.
Ex 3: CH2O with a molar mass of 240 g/mol

16. Determine the molecular formula
CH4N with molar mass 60 g/mol
CH2O with molar mass 150 g/mol
HgCl with molar mass 472 g/mol

17. Which have the same empirical and molecular formulas?
C2H4O2 and C6H12O6
NaCrO4 and NaCr2O7

18. Which is both an empirical and a molecular formula?
C5H10O5 (ribose)
C6H12O2 (ethyl butyrate)
C55H72MgN4O5 (chlorophyll)
C12H17ON (DEET)

19. C: 19 Nov. 2010 Take Out: % Water in a Hydrate Lab Handout
Objective: SWBAT calculate the percent water in a hydrate and determine the hydrate’s molecular formula.
Do now: Which pair of formulas have the same empirical formula? What is it?
C2H4O2 and C6H12O6
NaCrO4 and NaCr2O7

20. Agenda Do now Pre-lab discussion, safety and using a Bunsen burner
Lab calculations and conclusions
Homework: Complete lab packet (#5 is optional): Mon.
Advance notice: Test Weds.

21. Lab – water of hydration
Hydrate – An ionic compound that contains water molecules as part of its crystal structure
Naming/writing formulas
CaCl2 •2H2O – Calcium Chloride dihydrate
This is a compound where each molecule of calcium chloride is combined with 2 molecules of water in the crystal structure
The prefixes are the same as for naming compounds

22. Lab – water of hydration
Anhydrous – The form of a hydrate- forming compound with NO water in its structure
Salt – Any ionic compound

23. Lab – water of hydration
Objective: To determine the percentage of water in a hydrate, and to calculate the ratio of the number of moles of water to the number of moles of anhydrous salt molecules.
You will be removing the water from a hydrate and calculating how much water was in it and then using that value to calculate the formula for the compound
CuSO4·XH2O(s) CuSO4(s) + H2O(g)

24. Using a Bunsen burner
Be sure the gas valves at your station are turned off.
Attach the black tubing to the gas outlet at your station and attach the other end to your Bunsen burner. Be sure the tubing is attached securely.
Open the gas valve at your station. You should hear a soft hissing sound.
Immediately, hold the flint lighter above, and at an angle to, the top of your Bunsen burner. Squeeze to produce a spark.

25. Using a Bunsen burner
If the flame is not immediately ignited, turn off the gas at your station and wait several minutes until the gas has dissipated before trying again.
Once lit, turn down the gas at the station, and then use the airflow adjustments on the Bunsen burner to produce a quiet flame with smooth edges and two distinct cones: a darker blue cone inside a lighter blue cone.
To extinguish the flame, turn off the gas at your station.
NEVER leave the Bunsen burner lit unless you are actively using it!

26. Lab – % Water in a Hydrate
Never set a hot object directly on the lab bench: place it on a wire mesh.
Never place a hot object on a balance. Let it cool to the touch first.
Heat with the cover OFF, cool with the cover ON.
Be careful not to burn your substance. Stir and move the crucible in and out of the flame to evaporate evenly.
A hot crucible and a cool crucible look the same!!

27. Goggles stay on for the entire lab, until your area is completely clean.
When you finish the lab, clean up your area completely.
Return clean, dry equipment to the front table.
Then, sit down with your group and begin calculations.

28. Homework
Lab worksheet due Monday with all completed calculations. Show all work! (#5 optional)
Test Weds.
You will be writing a formal lab report – started in class next week.

29. A: 19 Nov. 2010
Take Out Homework: Week 11 #6-10 and Hydrates Lab worksheet!
Objective: SWBAT calculate an empirical formula from lab data, and write a lab report for the hydrate lab.
Do now: What is the molecular formula for the compound with empirical formula PCl2 and molar mass 306 g/mol?

30. Agenda Do now Homework solutions Empirical formula practice problems
Lab report writing overview
Lab report work time
Homework: Finish Week 11 Homework,
Lab report 1st draft due Friday, Dec. 3

31. Finding Empirical Formula in the Lab
When we do Analytical Chemistry in the lab, we can find values for the amount of a certain element in a compound
Like when we found the amount of water in CuSO4 • XH2O
We have a system for taking the values we get in the lab and figuring out the empirical formula

32. STEP 2 - Convert each mass value into moles
Determine the empirical formula for a compound that is 74.83% carbon and 25.17% hydrogen by mass
STEP 1 - Pretend you have 100 grams of the substance, make the % values into numbers of grams
STEP 2 - Convert each mass value into moles
STEP 3 - Divide all mole values by smallest # of moles
STEP 4 - Use the resulting numbers as your subscripts

33. Determine the empirical formula for a compound that is 25
Determine the empirical formula for a compound that is 25.9% nitrogen and 74.1% oxygen.
STEP 1 - Pretend you have 100 grams of the substance, make the % values into numbers of grams
STEP 2 - Convert each mass value into moles
STEP 3 - Divide all mole values by smallest # of moles
STEP 4 - Use the resulting numbers as your subscripts

34. Finding Empirical Formula
Sometimes you won’t be given percentages, but values for each element out of a total value
Ex: What is the empirical formula for a compound where a 10.0 g sample contains g O and 0.59 g H?
To solve: Just write down the number of grams of each, then proceed as before.

35. Practice Problems
Calculate the empirical formula of a compound composed of 79.8% C and 20.2% H
Calculate the empirical formula of a compound composed of 67.6% Hg, 10.8% S and 21.6% O.
Calculate the empirical formula of a compound where a 50.0 gram sample contains 29.4 g of C, 4.90 g H and 15.7 g O.
Calculate the molecular formula of the compound in #3 if the molar mass is g/mol.

36. For the rest of class… Choose one section
Spent the rest of this period (quietly!) making a rough draft in your notebook
I’ll pass back papers

37. Homework! Week 11 HW, # 11 – 15: Fri.
Lab report first draft: Friday. Dec. 3

38. C: 23 Nov. 2010 Take Out Homework: Week 11 #9-16
Objective: SWBAT solve all types of “determine the formula” problems.
Do now: Put these steps in order to solve a “calculate the empirical formula” problem:
Divide all numbers by the smallest number of moles.
Change % to grams
Round to the nearest whole number and use that number as the subscript
Divide by atomic mass to get moles

39. Agenda Do now Homework solutions Lab report rubric
“Determine the formula” self-assessment
Practice Problems
Unit Review Game!
Test Wednesday
Homework: Finish Practice Section III
(Section IV is optional but helpful!)
Lab report: Due next Friday

40. C: This week Today: Extra help after school!!! 3:30-4:30 Room 203
Wednesday: Unit Test
Atoms/molecules  moles  mass problems
Determining empirical/molecular formulas
Thursday/Friday: No class! 
Next week Mon: Lab report work time (we just ran out of time this week)

41. Hand out lab report rubric

42. Title
Your lab report should be titled with a title of your choosing.
It should be relevant to the lab and should not just be the same as the title of a handout your teacher gave you.
Do not have it on a separate title page.
Include your name, the date, class section and the names of your lab partners
Background Information
Provide an overview of necessary information
Explain any important concepts that are central to understanding the experiment.
In paragraph form, define any scientific terms necessary for understanding the lab.
Link these concepts and terms together into a coherent paragraph
Objective
State the reasons for the experiment
Explain what the purpose of the experiment or what goals you have in completing the lab. What do you hope to accomplish?

43. Summary of Procedure
Summarize what you did
Write a summary of what you did. Do not rewrite the given procedure word for word. The summary should be in paragraph form and, ideally, in past tense.
Include a labeled diagram of the experimental set-up.
Data and Results
Present the results of your experiment.
Include a data table that shows what data you collected. Be sure it shows what each number means!
Data should be presented neatly!
Include all calculations you did. Show each step and a short description of what you did for each step.
Include paragraph(s) of qualitative data and descriptions.

44. Analysis
Discuss patterns and trends in the data
Describe what your data mean. That is, what do the results of your calculations tell you?
Describe what your qualitative observations mean.
Conclusions
Explain what you can draw from the data
Was the experiment successful at completing the objectives above? Explain why or why not.
Calculate the actual percent water by mass of CuSO4·5H2O.
Compare your percent water to the actual percent water by calculating percent error. Show your calculations.
Describe all sources of error in the experiment. Explain how they affected your data (for example, did they make your mass of water increase or decrease? Did this make your moles of water increase or decrease? Did this make your number of molecules of water increase or decrease? Be specific!)
Explain how each of your errors could be minimized and improved.

45. Self-Assessment
Silently, on your own, solve the first three problems (Type A, B and C) and check your answers. (12 min.)
Work on Section II: Use the results of Section I to determine which types of problems you need to practice most!
For example, if you got “Type A” wrong in Section I, do Section II, Type A.

46. After you take the self-assessment…
Parts of Section II are optional, but recommended if you got any of Section I wrong.
You MUST complete Section III – Mixed Practice, and check your answers.
Section IV is optional (but recommended!) – Practice Quiz, and check your answers.
Anything you don’t finish by the end of 1st period is homework

47. Homework Test Wednesday
Finish Practice Problems Section III: due tomorrow
Section IV is optional, but a great way to study!
Study your mass-moles-atoms/molecules quiz, and redo problems you got wrong
Lab report: Due next Friday

48. 24 Nov. 2010
Objective: SWBAT show what you know about moles conversions and determining formulas on a test!!
Questions?

49. Periodic table is on the last page. You can rip it off!
When you are finished, do one of the following:
Begin working on your lab report first draft in your notebook.
Lab report work day Monday!
Begin working on extra credit problems. (due Monday!)

50. Lab report work time
Save your work to a USB or to your , NOT to the desktop or laptop!!
Stay in your seat and work quietly.
Follow the checklist!!
Raise your hand if you have questions.
Lab report due Friday, December 3 in class.