1. Unit B – Analytical Stoichiometry
Lundquist

2. Unit B.1
Gravimetric analysis

3. Mass Spectrometer

4. Lots of Arguing <1850 the mass of atoms was based on Hydrogen
H = 1 atomic mass unit
used Oxygen
O = 16 amu
Making H of O
Small problem (1919) isotopes (O with a mass of 17 & 18)
Made 2 different systems (O and O)
1961 based off 𝐶
Was already a base in physics for masses
More stable isotope
1 amu = mass of 𝐶 nucleus

5. 6 12 𝐶 6 13 𝐶 Carbon-13 Carbon-12 Carbon with a mass of 13 6 protons
7 neutrons
Carbon-12
Carbon with a mass of 12
6 protons
6 neutrons

6. Average Atomic Mass Number of protons (+) charge in the nucleus
Number of e- if neutral
Average atomic mass
Isotopes (heavier/lighter atoms)
Weighted average

7. Average Atomic Mass
𝐴𝑣𝑒𝑟𝑎𝑔𝑒.𝐴𝑡𝑜𝑚𝑖𝑐.𝑀𝑎𝑠𝑠=( 𝑚 1 % 1 )+( 𝑚 2 % 2 )+( 𝑚 3 % 3 )...
Mass of isotope
Percent abundance as a decimal

9. ADVANCED PROBLEM
A sample of argon contains 2 isotopes 39 𝐴𝑟 and 40 𝐴𝑟 , given the average atomic mass of argon what is the percent abundance of each isotope?

10. B.1 Note Quiz Questions 1.

11. The mole
Number of carbon atoms in exactly 12.0 g of 12 𝐶
6.022 x 1023

13. Molar Mass (Formula Weight)
The mass of x 1023 ___________ of a substance
Atoms if an element (Au, C, Hg)
Molecules
compounds (C6H12O6, CO2, H2O)
Polyatomic elementals (O2, S8, P4)
Formula units if a salt (CaO2, NaCl, MgSO4)

15. B.1 Note Quiz Questions 2. 3. 4. 5.

17. Percent Composition Percent by Mass Mass percent
What part of a substance’s matter is a particular element
Molar mass including subscripts

18. Percent by Mass
What is the percent by mass of each element in ethanol (C2H5OH)

20. B.1 Note Quiz Questions 6. 7. a. b. c. d.

21. When in doubt, burn it.

22. Formulas Empirical Formula Molecular Formula
Simplest ratio of each element
For ionic compounds (salts) there is only empirical formulas
Actual number of each element present
For molecular compounds (all non-metals)

23. B.1 Note Quiz Questions 8. a. b. c. d.

24. The Poem By Mrs. Freeman Percent to mass Mass to mole Divide by small
Multiple till whole

25. Example
A white powder is analyzed and found to contain 43.64% P and 56.36% O by mass. The compound has a molar mass of g/mol. What are the compound’s empirical and molecular formulas?

26. B.1 Note Quiz Questions 9.
10.

27. Problem
A compound is composed of carbon, nitrogen, and hydrogen. When g of this compound is reacted with oxygen, g of carbon dioxide, and g of water are collected. Determine the empirical formula of the compound.

28. Problem (continued)
A compound is composed of carbon, nitrogen, and hydrogen. When g of this compound is reacted with oxygen, g of carbon dioxide, and g of water are collected. Determine the empirical formula of the compound. If the molar mass of the is 31 𝑔 𝑚𝑜𝑙 what is the molecular formula?

30. Hydrates Also known as dot waters
CoCl2 & CoCl2.6H2O
Water molecules can fit between the ions of a salt
Anhydrous – no water
Hydrate – water is present
Can pull out the water with heat

31. Hydrates
A calcium chloride hydrate has a mass of 4.72 g, after heating for several minutes the mass of the anhydrate is found to be 3.56 g. Determine the formula of the hydrate.

32. Unit B.2
Stoichiometry
(5 Note quiz questions – short w/ lots of practice)

33. Stoichiometry 2 parts for this unit
Analytical / gravimetric stoichiometry
Determine the formula from data
Solids & gas stoichiometry
Stoichiometry
Determine the amount of products produced
Determine the amount of reactants needed
Do you have enough of both?
LOTS of ways of doing it FIND ONE THAT WORKS FOR YOU!
ALL MUST HAVE A BALENCED EQUATION

34. Balancing S8 + H2 → H2S Do an atom inventory
Subscripts apply to what is INFRONT of them
H2O
Mg(NO3)2
Coefficients apply to what is BEHIND them
2 H2O
6Mg(NO3)2
S8 + H2 → H2S

35. Balancing
Change ONLY the coefficients to INCREASE numbers of each element so that the Rxts = Prod.
S8 + H2 → H2S

36. Tips CuNO3 + Al → Al(NO3)3 + Cu H2SO4 + NaOH → H2O + Na2SO4
Keep polyatomic ions together!
If water and hydroxide (OH-) are present write water as HOH
CuNO3 + Al → Al(NO3)3 + Cu
H2SO4 + NaOH → H2O + Na2SO4

37. Tips
Save anything elemental for last
S8 + O2 → SO3

38. Tips
If stuck double EVERYTHING
C8H18 +O2 → CO2 + H2O

39. KNOW

40. Balancing Chemical Equations

41. THIS IS A SKILL You will get better with PRACTICE GO ONLINE
Find practice in your packet
FRQ 1982
Do the handout

42. SAMPLE PROBLEM 1 C3H8 + 5 O2 → 3 CO2 + 4 H2O C3H8 + O2 → CO2 + H2O
Calculate the mass of oxygen that will react completely with 96.1 grams of propane
Write a reaction
Balance it
1 C3H8 + 5 O2 → 3 CO2 + 4 H2O
C3H8 + O2 → CO2 + H2O

43. B.2 Note Quiz Questions 1. 2. 3.

44. SAMPLE PROBLEM 1 C3H8 + 5 O2 → 3 CO2 + 4 H2O C3H8 + O2 → CO2 + H2O
Calculate the mass of oxygen that will react completely with grams of propane
3. Determine number of moles
4. Determine number of moles of product
1 C3H8 + 5 O2 → 3 CO2 + 4 H2O
C3H8 + O2 → CO2 + H2O

45. 1.) Dimensional analysis
Calculate the mass of oxygen that will react completely with 96.1 grams of propane
1.) Dimensional analysis
START WITH A PLAN
[…] moles A to moles B […]
The plan becomes the top of you chart, previous units become your bottom

46. 1.) Dimensional Analysis
C3H8 + 5 O2  3 CO2 + 4 H2O

47. Calculate the mass of oxygen that will react completely with 96
Calculate the mass of oxygen that will react completely with 96.1 grams of propane
2.) mole map

48. 2.) mole map
C3H8 + 5 O2  3 CO2 + 4 H2O

49. 3.) Round about C3H8 + 5 O2  3 CO2 + 4 H2O Find moles
Place moles under BALANCED equation
Going up divide, moving down multiply
C3H8 + 5 O2  3 CO2 + 4 H2O
Calculate the mass of oxygen that will react completely with 96.1 grams of propane

50. 4.) Renee’s Table  Equation C3H8 5 O2 3 CO2 4 H2O Moles Conversion
Calculate the mass of oxygen that will react completely with 96.1 grams of propane
4.) Renee’s Table
MAGIC
Equation
C3H8
5 O2 
3 CO2
4 H2O
Moles
Conversion
Given/wanted

51. B.2 Note Quiz Questions 4. 5.

52. Unit B.3
Limiting Reagents/Reactants

53. Limiting Reagents
What limits how many hot dogs everyone can have?

54. Limiting Reagents
The reactant that is consumed first, limiting the amount of product that can be formed
Required you to do the problem twice (maybe thrice)
Determine the amount of product that each reactant can form

55. Practice

56. B.3 Note Quiz Questions 1. 3. 2.

57. Yields Theoretical Yield Experimental Yield
The amount of reactant/product from the stoichiometry
math
Expectation
The amount of reactant/product from an EXPERIMENT
Reality

58. Why Typically because of human error Products are not dry
Loss from splatter/spills
Residue in transfers
Imperfect conditions

59. %𝑦𝑖𝑒𝑙𝑑= exp𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 𝑠𝑡𝑜𝑖𝑐ℎ𝑖𝑜𝑚𝑒𝑡𝑟𝑦 ×100
Percent Yield
%𝑦𝑖𝑒𝑙𝑑= exp𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 𝑠𝑡𝑜𝑖𝑐ℎ𝑖𝑜𝑚𝑒𝑡𝑟𝑦 ×100
How much you produced
In a perfect world = 100% (it’s never 100% -- reality sucks)

60. Practice 2AgCl + Cu  CuCl2 + 2Ag
A student performs the reaction above with 0.932g Cu, if 2.98g Ag is captured, what is his percent yield?
Another student captured g of Ag, what is her percent yield?

61. B.3 Note Quiz Questions 4.
If a student carries out the reaction of benzene with nitric acid seen to the left, and from 7.8g of benzene obtained a 33% yield what mass of water did they produce?
a. 0.3g
b. 0.6g
c. 1.2g
d. 1.8g 5.

62. Lab Next Period, Test after that
Quiz
Write a balanced equation
Determine the moles of product from quantities of a gas
Determine the LR
Percent by mass
Excess of remaining
Predict change due to error
Lab
Determination of the formula of a hydrate
BEFORE LAB:
Do prelab
Watch lab procedure