1. Drill /27/14
Laughing gas (N2O) is sometimes used as anesthetic in dentistry. It is produced when ammonium nitrate is decomposed according to the following reaction:
NH4NO3 (s) → N2O (g) + 2 H2O (l)
How many moles of NH4NO3 are required to produce 33.0 g N2O?

2. Answer
0.750 mol NH4NO3

3. Drill?? 3/10/2014
Define percent composition…

4. Objectives: SWBAT
Convert between mass or volume and number of moles for a given substance.
Convert between number of moles and number of particles for a given substance.
Determine empirical and molecular formulas.

5. Announcement
Stoichiometry Test
Pd 4B – Friday
Pd 4A - Monday

6. Agenda
Percent Composition
Empirical Formula
Molecular Formula

7. Percent Composition

8. Percent Composition
The percentage by mass of each element in a compound
% element in compound =
(mass of element in sample of compound / total mass of sample of compound) * 100

9. Drill – pd 4A
Any questions about worksheets?

10. Agenda
Quiz
Empirical and Molecular Formulas
Day 2 of Lab

11. Reminder…
Must be in seats with electronic device put away by the time the second bell rings.

12. Drill pd /13/15
What is the first step when determining the empirical formula of a compound?
Assume a g sample so that the percentage values can be converted to grams.

13. Empirical Formula

14. Empirical Formula
Simplest positive integer ratio of atoms present in a compound
Percent composition can be used to determine the formula

15. Percent
Composition
Mass
Composition
Composition
in moles
Smallest
whole-number
mole ratio

16. to determine empirical formulas…
Assume that you have a g sample so that the percentage values can be converted to grams.
Convert the grams to moles
Divide each number of moles by the smallest number.
If necessary, multiply these numbers by integers in order to get whole numbers; if an operation is done to one of the numbers, it must be done to all of them.

17. Mass composition (in 100.0g) = 32.4 g Na, 22.6 g S, 45.0 g O
What is the empirical formula if a compound contains 32.4% Na, 22.6% S, & 45.0% O?
Mass composition (in 100.0g) =
32.4 g Na, 22.6 g S, 45.0 g O
Composition in moles =
32.4 g Na x (1 mol Na / g Na) = 1.41 mol Na
22.6 g S x (1 mol S / g S) = mol S
45.0 g O x (1 mol O / g O) = 2.81 mol O
Smallest whole-number mole ratio
Na: / .705 = 2.00
S: / .705 = 1.00
O: / .705 = Na2SO4

18. Sample Problem
Determine the empirical formula of a compound containing g Au and g Cl.

19. Answer
AuCl

20. Sample Problem
Determine the empirical formula of a compound given the following mass percent composition: 49.5% C, 5.2% H, 28.8% N, and 16.5% O.

21. Answer
The formula is C4H5N2O

22. Molecular Formula

23. Molecular Formula
A compound’s empirical formula can be used to determine its molecular formula (number and type of atoms that are present in a single molecule of a substance. )
Ratio = given formula mass
empirical formula mass
Use number from ratio to multiply subscripts

24. So… CH  C6H6 Molecular formula mass = 78.11 g
Determine the molecular formula of the compound with an empirical formula of CH and a mass of g.
Molecular formula mass = g
Empirical formula mass =
C + H = g g = g
Ratio = g/13.02 g =
So… CH  C6H6

25. Classwork/Homework Percent Composition
Determining Empirical Formulas WS 1-5
Determining Molecular Formulas WS 1-4

26. Drill #31 3/8/2012
What ratio or conversion factor is used in all conversion problems?

27. Announcement Remove everything from your desk except for a pencil.
I will provide periodic table for you to use.
Remember to show all work
After you are finished with test, bring to me and work quietly on something else or take a nap.
Leave one empty desk between you and your classmate – can use lab area.

28. Drill #30 3/7/2012 List the 3 steps used to write an empirical formula
Turn in drill sheets

29. Agenda Work quietly on Review WS No socializing
I will post answers to Review WS on my webpage today after school.

30. Announcements Test tomorrow, March 8, 2012 Topics include:
Mole-to-mole conversion probs
Mass-to-mass conversion probs
Volume-to-mass conversion probs
Limiting Reactant probs
Empirical formulas

31. Drill /6/2012
Determine the mass of P4O10 formed if 25.0 g of P4 and 50.0 g of O2 are combined.

32. Drill – 3/6/2012
Determine the mass of P4O10 formed if 25.0 g of P4 and 50.0 g of O2 are combined.
57.3 g P4O10

33. No Drill Today /9/12 I’ll give you a half sheet of paper and complete ON YOUR OWN – extra credit for test. Can use your notes. Have 10 mins.
How much chlorine (g) should be produced if 84.2 grams of aluminum chloride and 68.4 grams bromine are combined?
AlCl3 + Br AlBr3 + Cl2

34. Mole Conversions Graphic Organizer
Place in notes
Conversion factor for liters:
22.4 L/1 mole

35. Volume
1 mol of any gas at STP (standard temperature and pressure) is equal to 22.4 L