1. Analytical Chemistry!!!!

2. Recall Mole—unit of measurement used to measure a quantity
1 dozen = 12 doughnuts
1 mole = 6.022*1023 atoms or molecules of a substance
Avogadro’s number—proportion that relates molar mass of a substance to the mass.
Used 12 g of Carbon-12 as a standard
2 g of H2 has the same number of molecules as 12 g of C.

3. Moles to Particles
Can find moles of a substance given the number of particles and visa versa.
Examples
Find the number of particles in 2 mol of Fluorine gas.
Find the number of moles of 5.63*1023 molecules of ammonia.

4. Mass to Moles 10 feathers has a different mass than 10 bowling balls
1 mol of one substance has a different mass than 1 mol of another substance.
Molar mass—mass of 1 mol of a substance
equal to the atomic mass of an element
units are grams per mole or g/mol
when you weigh out that many grams of a substance you have x atoms

5. Mass to Moles
Use molar mass as a conversion factor between mass and moles.
Example: Find the number of moles of 3.00 g of C.
Example: Find the mass of 4.23 moles of C.

6. Moles of Compounds
Chemical Formula – indicates the types and number of atoms present in a compound—also represents a mol ratio of elements in the compound.
1 mol of CH4 would consist of x 1023 molecules of CH4
or 1 mol C atoms, 4 mol of H atoms (remember 1 mole = atomic mass)
Calculate the number of moles of each element in 5 mol of glucose (C6H12O6)

7. Molar Mass of Compounds
The mass of a briefcase could be obtained by the sum of the case + mass of each of the contents within.
The mass of a mole of a compound equals the sum of the masses of each particle that makes it up.
This is used to measure moles of a substance in laboratory experiments.

8. Mole calculations How many grams are in 6.7 mol of Aluminum Chloride?
How many moles are in 3.4*1024 molecules of Sodium Hydride?
How many molecules are in 2.35 g of Hydrogen gas?
How many grams are in 5.4*1023 molecules of Sodium Chloride?
How many Al3+ and Cl- ions are there in a g sample of AlCl3?
What is the mass of 1 formula unit of AlCl3?

9. Percent Composition
The % composition of a compound is always the same, regardless of the size and source of the sample.
What is the percent composition of KMnO4?

10. Aspartame is used in as an artificial sweetener in brands such as Equal and Nutrasweet. Its chemical formula is C14H18N2O5
Calculate the mass percentage of each element in aspartame.
Calculate the mass of carbon in a 1.00 g packet of Equal, assuming it is pure aspartame.

11. Empirical Formulas
Remember, empirical formula is the smallest whole number ratio of atoms (aka a simplified version of the molecular formulas).
4 steps when given % composition.
Assume the sample is out of 100 g and convert percentages to masses.
Convert masses to moles.
Divide moles by lowest number of moles (if you need to convert these values to whole numbers, now is the time to do it.)
Use moles for each element as subscripts for that element.

12. An unknown compound was found to have a percent composition as follows: 47.0 % potassium, 14.5 % carbon, and 38.5 % oxygen. What is its empirical formula?

13. Formulas from Mass
Use masses to find moles of each substance and go from there.
A sample of indium chloride weighing g is found to contain g of chlorine. What is the empirical formula of the indium compound?

14. Molecular formulas
Specifies that actual number of each atom in that molecule.
Remember many compounds can have the same empirical formula, but different molecular formulas.
Empirical Formula
Molecular formula
Name of Molecule
Boiling Point (oC)
CH2O
Formaldehyde
-21
C2H4O2
Acetic Acid
117
C3H6O3
Glyceraldehyde
140

15. Find the empirical formula from the following molecular formulas:
C6H6
C8H18
WO2
C2H6O2
X39Y13

16. Glucose undergoes chemical analysis and is found to have a molar mass of g/mol and is composed of % C, 6.70% H, and 53.40% O. Find the empirical and molecular formulas.

17. Hydrates
A chemical compound containing water that is chemically combined with a substance and can usually be expelled without  changing the constitution of the substance.

18. Uses for hydrates Anhydrous compounds—without water
Used as dessicants—drying agents
Anhydrous compounds absorb water
Can be added to solvents to remove water

19. Nomenclature for Hydrates
Examples: CuSO4· 5H2O 1.) Use name of compound: Copper (II) Sulfate. 2.) Name hydrate with correct prefix: Di = 2 Tri = 3 Tetra = 4 Penta = 5 Hexa = 6 Hepta = 7 Octa = 8 Nona = 9 Deca = 10

20. Practice
CuCl2∙2H2O
BeSO4∙4H2O
MgSO4∙7H2O
CaSO4∙6H2O

21. More practice cobalt (II) fluoride tetrahydrate
 lithium nitrate trihydrate
 aluminum hypochlorite octahydrate
 cesium carbonate dihydrate

22. Finding formulas for hydrates
Must use anhydrous form of compound.
1.) Drive off water by heating.
2.) Use mass of anhydrous compound to calculate moles.
3.) Calculate mass of water and then find moles of water.
4.) Use mole ratio of anhydrous compound:water to write formula.

23. Empirical Formulas of Hydrates
What is the formula of a hydrate that is 86.7% Mo2S5 and 13.3% H2O? What is the name?
What is the formula for a hydrate that is 90.7g SrC2O4 and 9.30g H2O?
A sample of hydrated Li2SiF6 weighs grams. After heating, the anhydrous compound has a mass of grams. Find the formula of the hydrate.