1. Stoichiometry & the Mole

2. Part 1
The Mole

3. Dimensional Analysis Review
How many seconds are in 5.0 hours?

4. Stoichiometry
Stoichiometry is just a long word for changing units in chemistry
If you can do Dimensional Analysis, you can do stoichiometry

5. The Mole
Chemists need a convenient method for counting accurately the number of atoms, molecules, or formula units in a sample of a substance.
The mole, commonly abbreviated mol, is the SI base unit used to measure the amount of a substance.

6. The Mole A mole of anything contains 6.0221367 x 1023 particles.
A particle may be atoms, molecules, formula units, electrons, or ions.
In this class, Avogadro’s number will be rounded to four significant figures— x 1023.

7. Just How Big is a Mole?
Enough soft drink cans to cover the surface of the earth to a depth of over 200 miles.
If you had Avogadro's number of unpopped popcorn kernels, and spread them across the United States of America, the country would be covered in popcorn to a depth of over 9 miles.
If we were able to count atoms at the rate of 10 million per second, it would take about 2 billion years to count the atoms in one mole.

8. A Mole of Particles Contains 6.02 x 1023 particles
= x 1023 C atoms
= x 1023 H2O molecules
= x 1023 NaCl “molecules”
(technically, ionics are compounds not molecules so they are called formula units)
6.02 x 1023 Na+ ions and
6.02 x 1023 Cl– ions
1 mole C
1 mole H2O
1 mole NaCl

9. Conversion Factor #1
Remember that you can flip this conversion factor

10. Mole Map Atoms or Molecules Moles 1 mole 6.02 X 1023 particles

11. Mole –Particle Calculations
Calculate the number of atoms in 3.50 moles of copper

12. Mole –Particle Calculations
How many moles of MgO are in 9.72 x formula units of MgO?

13. Mole – Mass Relationship
The mass in grams of one mole of any pure substance is called its molar mass.
The molar mass of any element is numerically equal to its atomic mass and has the units g/mol.

14. Molar Mass of Compounds
The molar mass (MM) of a compound is determined by adding up all the atomic masses for the molecule (or compound)
Ex. Molar mass of CaCl2 20
Ca 
17 Cl 35.45

15. Practice Calculate the Molar Mass of calcium phosphate Ca3(PO4)2
Formula =
Masses elements:
Molar Mass =
Ca3(PO4)2

16. Calculating Molecular Mass
What is the molar mass of (C3H5)2S?
What is the molar mass of BeC2O42H2O?

17. Conversion Factor # 2 1 mole Molar mass (g)
The molar mass comes from the periodic table!
Remember, you can flip the conversion factor to go the other way!

18. Mole – Mass Calculations
What is the mass of 4.21 moles of iron (III) oxide?

19. Mole – Mass Calculations
How many moles of Ca(OH)2 are in 325 grams?

20. Learning Check!
The artificial sweetener aspartame (Nutra-Sweet) formula C14H18N2O5 is used to sweeten diet foods, coffee and soft drinks. How many moles of aspartame are present in 225 g of aspartame?

21. Mole Map Atoms or Molecules Moles Mass (grams) Molar Mass 1 mole
6.02 X 1023 particles
1 Mole
Molar Mass
6.02 X 1023 particles
1 mole
Moles

22. Everything must go through Moles!!!
Calculations
molar mass Avogadro’s number Grams Moles particles
Everything must go through Moles!!!

23. Mass – Particle Conversions
How many atoms of gold are in 25.0 g of gold?

24. Mole-Liters
STP
Temperature = 298 K
Pressure = 1 atm
At standard temperature and pressure (STP), one mole of gas (no matter what the gas is) occupies 22.4 liters of space.

25. 1 mole 22.4 Liters This is ONLY true at STP
Conversion Factor #3
1 mole 22.4 Liters This is ONLY true at STP

26. Mole Map Atoms or Molecules Moles Mass (grams) Liters of GAS (at STP)
Molar Mass
1 mole
1 mole
6.02 X 1023 particles
1 Mole
Molar Mass
6.02 X 1023 particles
1 mole
Moles
22.4 Liters
1 mole
1 Mole
22.4 Liters
Liters of GAS
(at STP)

27. Mole – Liter Calculations
What is the volume of 4.21 moles of carbon dioxide gas at STP?

28. Mole Map Atoms or Molecules Mass (grams) Liters (at STP) Molar Mass
6.022 X 1023
Molar Mass
Multiply with the arrows
Divide against the arrows
22.4
Liters (at STP)

29. Mixed Practice Calculate the molar mass of the following 1. C3H5N3O3
2. Al(NO3)3
SO2

30. Mixed Practice 4. 5.49 mol of KI 5. 0.354 mol of Fe3(Fe(CN)6)2
Calculate the mass in grams of each of the following
mol of KI
mol of Fe3(Fe(CN)6)2
mol of Ca(NO3)2.3 H2O

31. Mixed Practice
Calculate the number of moles in each of the following: g of Na2S g of C16H18N2O4S g of K2SO4

32. Calculate the number of atoms, molecules, or ions for each of the following mole of CO2, number of molecules g of H2S, number of molecules mole of Mg+2, number of ions

33. Calculate the number of grams in each of the following:
1.50 X 1023 ions of Na+
X 1023 atoms of S
X 1024 molecules of H2O

34. Practice Problems (Calculator Free)
A balloon is filled with 1.0 mole of CO2 at STP.
What is the balloon’s mass?
What is the balloon’s volume?
How many molecules are in the balloon?

35. Practice Problem #2 (Calc. Free)
A student measures out moles of Radon, how many atoms of radon did the student measure out?

36. Practice Problem #3 (Calc. Free)
The mass of X 1024 atoms of hydrogen gas is equal to ____________.

37. Practice Problem #4 (Calc. Free)
The mass of 3.01 X 1023 molecules of gas is 18.0 grams. What volume does 12.0 grams of the gas occupy at STP?

38. Practice Problem #5 Who am I?
A 22 gram sample of me contains 6.02 x 1023 atoms of oxygen
0.25 moles of me weighs 10.0 grams.
C12H22O11
Calcium sulfate
Carbon Dioxide
Water
Sodium hydroxide

39. Additions to the Mole Map
Liters of a liquid The number of moles in a liter of liquid can be found if the MOLARITY of the solution is known. Molarity = mole Liters
To go from liters to moles, multiply by this molarity. To go from moles to liters, divide by this molarity.

40. Mole Map Atoms or Molecules Moles Mass (grams) Liters of GAS (at STP)
Molar Mass
1 mole
1 mole
6.02 X 1023 particles
1 Mole
Molar Mass
6.02 X 1023 particles
1 mole
Moles
Molarity 1
22.4 Liters
1 mole
1 Mole
22.4 Liters 1
Molarity
Liters of GAS
(at STP)
Liters of liquid

41. Additions to the mole map
Gases not at STP (0 C and 1 atm) The equation PV=nRT is used P= pressure in atm V= volume in L N= moles of gas R=8.314 J/mol*K T=Temperature in Kelvin

42. Percent Composition, Empirical and Molecular Formula
Part II
Percent Composition, Empirical and Molecular Formula

43. Calculating Percentage Composition
Calculate the percentage composition of barium sulfate.
Step 1: Determine the molar mass of the compound.
Step 2: Divide the mass of the element in the compound by the total molar mass, then multiply by 100%.

44. Practice Problem
Find the percent composition of sodium nitrate.

45. Practice Problem (Calc. Free)
What is the percent oxygen in potassium chlorate (molar mass 123 g/mol)?

46. You try! Determine the percent composition of NaCl.
Determine the percent composition of water.

47. Formulas
Empirical formula: the lowest whole number ratio of atoms in a compound.
Molecular formula: the true number of atoms of each element in the formula of a compound.
molecular formula = C6H6
empirical formula = CH

48. Formulas (continued)
Formulas for ionic compounds are ALWAYS empirical (lowest whole number ratio).
Examples:
NaCl
MgCl2
Al2(SO4)3
K2CO3

49. Formulas (continued)
Formulas for molecular compounds MIGHT be empirical (lowest whole number ratio).
Molecular:
H2O
C6H12O6
C12H22O11
Empirical:
H2O
CH2O
C12H22O11

50. Practice Problem Which of the following are NOT empirical formulas?
K2CO3
C6H12O6 (glucose)
H2O (water)
C2H4

51. Empirical Formula Determination
If given percentages (%) convert these to grams by assuming a 100g sample.
Convert grams to moles.
Divide each value of moles by the smallest of the values.
If the resulting answers contain numbers other than whole numbers, you will have to multiply them all by the same # to get whole #s.

52. Empirical Formula Determination
Practice Problem
Adipic acid contains 49.32% C, 43.84% O, and 6.85% H by mass. What is the empirical formula of adipic acid?

53. Practice Problem
A compound is found to contain 36.48% Na, 25.41% S, and 38.11% O. Find its empirical formula.

54. Practice Problem
Analysis of a g sample of a compound known to contain only phosphorus and oxygen indicates a phosphorus content of g. What is the empirical formula of this compound?

55. Practice Problem (Calc. Free)
A sample is analyzed and found to contain 24.0 grams C, 4.0 g H and 32.0 g O. What is the empirical formula?

56. Finding the Molecular Formula
The empirical formula for adipic acid is C3H5O2. The molar mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid?
Step 1: Find the molar mass of the empirical formula.
3(12.01 g) + 5(1.01) + 2(16.00) = g

57. Finding the Molecular Formula
The empirical formula for adipic acid is C3H5O2. The molar mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid?
Step 2: Divide the molar mass of the compound by the molar mass given by the empirical formula.
3(12.01 g) + 5(1.01) + 2(16.00) = g

58. Finding the Molecular Formula
The empirical formula for adipic acid is C3H5O2. The molar mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid?
3. Multiply the empirical formula by this number to get the molecular formula.
3(12.01 g) + 5(1.01) + 2(16.00) = g
(C3H5O2) x 2 =
C6H10O4

59. Practice Problem
What is the molecular formula of a compound that has an empirical formula of CH2 and a molar mass of 28 g/mol?

60. Practice Problem
A compound is 81.06% boron and 18.94% hydrogen. The molar mass was experimentally determined to be 54 g/mol. What is the molecular formula for the compound?