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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

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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

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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

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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.)

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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

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Density• Density= mass/volume

-Density can be used as a “conversion factor” as well!

Density

mass

volume

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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

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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.

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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.

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% 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.