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AP CHEMISTRYAP CHEMISTRY
Summer Review• Main Topics:
- Ch. 1/ sig. figs; conversion problems; density
- Ch 2/ counting p+, no, & e-; naming & writing formulas
- Ch. 3/ balancing eq.; % composition; empirical formulas
stoichiometry conversions; limiting reagents; % Yield
• Other:- Orbital diagrams; Dot notation
AP CHEMISTRYAP CHEMISTRY
Significant Figures• The number of significant figures is the number of digits known
with certainty plus one uncertain digit.
(Example: 2.2405 g means we are sure the mass is _______
but we are uncertain about the
nearest 0.0001 g.)
•Final calculations are only as significant as the least significant
measurement.
2.240 g
AP CHEMISTRYAP CHEMISTRY
Sig. Fig. Rules1) Nonzero digits are significant. (Nonzero Rule)
Example: 2.45 cm =________
2) Zeros between sig. figs. are significant. (Straddle Rule)
Example: 2.03 cm=_________
3) Zeros at the end of the number and after a decimal point are
significant. (Righty-Righty Rule)
Example: 7.850 cm=_________
3 s.f
4 s.f
3 s.f
AP CHEMISTRYAP CHEMISTRY
4) Zeros at the end of a number before a decimal point are
ambiguous…In some cases, a bar will be placed over a zero to
eliminate the ambiguity or the number will be written in scientific
notation. (Bar Rule)
Example: 10,300 grams = _____________
1.030 x 104 g = _________
5) If a number is known for certain, it is said to contain an infinite
number of sig. figs. (Counting Rule)
Example: 60 seconds =1 minute
at least 3 s.f.
4 s.f
(60 is known to ∞ # of s.f.)
AP CHEMISTRYAP CHEMISTRY
Significant Figures in Calculations• Multiplication and Division:
- Report to the least number of significant figures
Example: 6.221 cm x 5.2 cm = _______
• Addition and Subtraction:
- Report to the least number of decimal places
Example: 20.4 g – 1.322 g = _______
32 cm2
19.1 g
AP CHEMISTRYAP CHEMISTRY
Density• Density= mass/volume
-Density can be used as a “conversion factor” as well!
Density
mass
volume
AP CHEMISTRYAP CHEMISTRY
Counting p+, no and e-
• Protons = Atomic Number
• Electrons = protons (in a neutral atom)
• Neutrons = Mass # - protons
• Mass Number = protons + neutrons
Gaining electrons gives an atom a (-) charge.
Losing electrons gives an atom a (+) charge.
AP CHEMISTRYAP CHEMISTRY Naming Compounds
•Molecules– Contains only 2 nonmetals; covalent bonding.
General Format
Prefix (except mono)-name 1st element prefix-name 2nd element ending in –ide
AP CHEMISTRYAP CHEMISTRY
AP CHEMISTRYAP CHEMISTRY Naming Compounds
•Ionic– Starts with metallic cation (or NH4+); ionic bonding.
General Format
Cation Name Anion Name
You will have to memorize the cation and anion symbols & charges!
We will have a quiz over them later!
AP CHEMISTRYAP CHEMISTRY Naming Compounds
•Acids– Starts with “H”
AP CHEMISTRYAP CHEMISTRY Balancing Equations
•You can only change coefficients!
Example: C3H8 + __O2 __CO2 + __H2O 3 45
AP CHEMISTRYAP CHEMISTRY Percent Composition
100
Compound ofFW AWElement of Atoms
Element %
AW stands for the atomic weight of the atom from the periodic table.
FW stands for the formula weight of the compound.
AP CHEMISTRYAP CHEMISTRY Empirical Formulas
Helpful Rhyme: % to mass, mass to mole, divide by small, times ’til whole.
AP CHEMISTRYAP CHEMISTRY
Stoichiometry Conversion Factors
1 mole = 22.4 L (at STP) = 6.02 x 1023 particles = FW (grams)
•These conversions will take up to 3 steps and no more!
•Always convert to moles of given first!
AP CHEMISTRYAP CHEMISTRY Stoichiometry Conversions- (gram to gram)
AP CHEMISTRYAP CHEMISTRY Limiting Reagent (or Reactant)
•The reactant that runs out first “limits” the amount of product that can be formed.
•Stoichiometry conversions can be done to determine which substance is the limiting reagent.
AP CHEMISTRYAP CHEMISTRY
% Yield•The amount of product predicted from stoichiometry taking into account limiting reagents is called the theoretical yield.
•The percent yield relates the actual yield (amount of material recovered in the laboratory) to the theoretical yield:
100yield lTheoretica
yield ActualYield %
AP CHEMISTRYAP CHEMISTRY Electron Configurations
(Energy Level Diagrams)
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p…
Electron Configurations
(Energy Level Diagram)
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p…
↑↓
↑
↓
↓↓
↑
↑
↑
↑
↑↑ ↓ ↓
Silicon
AP CHEMISTRYAP CHEMISTRY Electron Dot Notation
•The “Group A” number on the periodic table equals the # of valence electrons and therefore the # of dots.