1. The Mole
2. Guy-Lussac
a. Found reacting volumes of gases react in whole number ratios
b. Found 1 volume of N reacted with 3 volumes of H to form ammonia
3. Avogadro (1811)
a. Started as lawyer, shifted to math and chemistry
b. Hypothesized elements could exist as polyatomic molecules
c. Concluded equal volumes hold an equal number of molecules
4. Avogadro’s Law
a. Equal volumes of a gases at the same temperature and pressure have the same number of molecules.
5. Canizzaro (1850)
a. Proved Avogadro’s Law for gases
b. Extended law to all states
i. Analyzed compounds to determine gram atomic mass
ii. Gram atomic or molecular mass always has same number of particles
6. The Mole
a. Mass on periodic table is in AMU
b. 1 amu is 1.66x10-24g
c. Derived by second law (F=ma)
7. Mass of 1 atom of Al
a. 26.98 amu/atom x 1.66x10-24 g/amu
b. 4.48x10-23g/atom
8. Atoms in 1 gram Atomic Mass
a. 26.98 g ÷ 4.48 x10-23 g/atom
b. 6.022 x 1023 atoms
c. Same value found for all elements and compounds
9. Molar Mass
a. Mass of 1 mole of particles
b. Atoms: from periodic table
c. Compounds: sum of atoms
10. Unit Conversion
11. Conversion Steps
a. 1. Determine given and desired units
b. Ex. What is the mass of 90 apples
i. Given: 90 apples
ii. Desired: mass
c. 2. Determine conversion sequence
i. Number ---> Dozens ---> Mass
12. Determine the conversion factor
a. A fraction equal to 1
b. 100 cm = 1 m
c. 100cm/100cm = 1m/100cm
d. 1 = 1m/100cm
13. Example Continued
a. 1. Known information:
b. Number of apples: 90
c. 1 dozen apples = 2.0kg
d. 2. Set up conversion factors
e. 1dozen apples/12 apples
f.
g.
14. Example Continued
a. Set up ratios and solve
b. 90 apples x 1dozen apples/12 apples x
c. 2kg apples/1 dozen apples
d. Cancel units and carry out math
e. 15 kg apples
15. Scientific Notation
a. Number of form Mx10n
b. 1 < M < 10
c. n is interger
i. + n is greater than 1
ii. - n is fraction
16. Why use it
a. Show the precision of the measurements.
17. Significant figure rules
a. Addition: set decimal places to least number used
b. Multipication: set significant figures to least used
18. Calculator Use
a. Set mode to “SCI”
b. Set float to 1 less than number of sig. figs.
c. Solve problem. Answer will have right number of sig.fig,
19. Molecular Mass
a. Mass of 1 molecule
b. Only for covalent compounds
c. Find sum of atoms in compound
20. Formula Mass
a. Mass of 1 formula unit
b. Used for ionic compounds
c. Find sum of atoms in compound
21. Molar Mass of Compound
a. Determine elements present and number of each
b. Determine mass of element (periodic table)
c. Multiply by number of atoms
d. Find sum
22. To Find Moles Present
a. Determine mol/g conversion factor
i. 1 mole/molar mass
b. Multiply by mass
23. To Find Mass Present
a. Determine g/mol conversion factor
i. Molar mass/1 mole
b. Multply by moles
24. Molarity
a. The number of moles in solution
b. Molarity (M) = moles of solute / Liters of solution
c. Text used dm3. In 1995 SI changed to accept L for liquids
25. Percentage Composition
a. Relative mass of elements in compound
26. Empirical Formula
a. Based on law of Definite Proportions
b. Atoms and moles present in same simple ratios
c. Gives simplest possible formula
27. Empirical Formula Steps
a. Find mass in grams
b. Find mass in moles
c. Find ratios
28. Molecular Formula
a. Give actual number of atoms with ratio
b. More accurate for organic compounds
29. Molecular Formula Steps
a. Find Molecular mass of compound
b. Determine mass of 1 empirical unit
c. Divide into molecular mass
d. Distribute quotient over empirical unit
30. Stoichiometry
a. The calculation of quantities in equations
31. Interpreting Chemical Equations
a. Particles:
i. Atoms: always conserved
ii. Molecules and moles not conserved
b. Mass: always conserved
c. Volume: not conserved
d. All may be used to calculate unknown quantities
32. Mass-Mass Relationships
a. How much is needed to combine with a known amount?
b. How much can be made from a known amount?
c. Problem: How many grams of AgCl can be produced using 17.0g of AgNO3 with excess NaCl?
33. Mass-Mass Steps
a. Write balanced equation
b. Find moles of known substance
c. Find ratio of known to unknown
d. Find moles of unknown
e. Find mass of unknown
34. Step 1: Write a balanced equation
a. AgNO3(aq) + NaCl (aq) -----> AgCl(cr) + NaNO3(aq)
35. Step 2: Find moles of the given substance
a. Mass given x 1mol/molar mass
b. 17g AgNO3 x (1 mol AgNO3 /170g AgNO3)
36. Step 3: Determine the ratio of the given to the unknown
a. Use the coefficients of the substances
b. 1 mol AgCl / 1 mol AgNO3
37. Step 4: Find moles of desired substance
a. Multiply the results of steps 2 and 3
b. 17g AgNO3 x 1mol AgNO3/170g AgNO3 x 1mol AgCl/1 mol AgNO3 = .1 mol AgCl
38. Step 5: Convert Moles to Grams
a. Moles x Molar Mass/1 mol
b. 0.1 mol AgCl x 144 g AgCl/1 mol AgCl = 14.4 g AgCl
c. This procedure can also be used to find volume and number of molecules
39. Limiting Reagent
a. The reactant completely consumed in a reaction
b. Use mass-mass to calculate required amount
c. If required is less than given then substance is limiting reagent
40. Percentage of Yield
a. Comparison of actual to expected yield
b. Step 1: calculate expected
c. Step 2: compare expected to actual
i. (actual/expected)x100