CHEM 151 Exam 3

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Chemistry: Atoms First
Chapters 6-9
updated 6 days ago by Sheyla_Villa
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1

Formal Charge Formula

# valence electrons - (# unshared electrons + 1/2 # shared electrons)

2

What is a resonance?

More than one valid Lewis Structure for a single molecule

3

Exceptions to Octet Rule

  1. Can have an incomplete octet
  2. Odd # of valence e-
  3. Expanded Octets
4

What does VSEPR stand for?

Valence

Shell

Electron

Pair

Repulsion

5

Rules for Electron Domains

  1. A single bond is considered to be one electron domain
  2. A double bond is considered to be one electron domain
  3. A triple bond is considered to be one electron domain
  4. A lone pair is considered to be one electron domain
6

Linear Molecule

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  • Has 2 bonds (2 e- domains)
  • 180o
  • Ex: CO2
7

Trigonal Planar

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  • 3 bonds (3 e- domains)
  • 120o
  • Ex: SO3
8

Tetrahedral

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  • 4 bonds (4 e- domains)
  • 109.5o
  • Ex: CH4
9

Trigonal Bipyramidal

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  • 5 bonds (5 e- domains)
  • 90o and 120o
  • Ex: PCl5
10

Octahedral

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  • 6 bonds (6 e- domains)
  • 90o
  • Ex: SF6
11

Bent 120o

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  • 3 e- domains and 2 bonds
  • Ex: SO2
12

Trigonal Pyramidal

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  • 4 e- domains and 3 bonds
  • 109.5o
  • Ex: NH3
13

Bent

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  • 4 e- domains and 2 bonds
  • 109.5o
  • Ex: H2O
14

See-Saw (Distorted Tetrahedral)

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  • 5 e- domains and 1 lone pair
  • Ex: SF4
15

T-Shape

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  • 5 e- domains and 2 lone pairs
  • Ex: ClF3
16

Linear

  • 5 e- domains and 3 lone pairs
  • Ex: IF3 -
17

Square Pyramidal

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  • 6 e- domains and 1 lone pair
  • Ex: BrF5
18

Square Planar

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  • 6 e- domains and 2 lone pairs
  • Ex: XeF4
19

Intermolecular Forces

  1. Dipole-Dipole interactions
  2. Hydrogen Bonding (Super Dipole-Dipole attraction)
  3. Dispersion (London) Forces
20

Dipole-Dipole

Partial positive of one molecule attracts partial negative of another molecule

21

Hydrogen Bonding (Super Dipole-Dipole attractions)

  • For molecules with hydrogen bonded to N, O, and F ONLY
  • N, O, F are the most electronegative elements (very polar bonds)
  • N, O, F, H are the smallest of atoms (get very close)
22

Dispersion (London) Forces

  • For nonpolar molecules
  • The attraction between tiny temporary induced charges
  • All molecules have London Forces
23

Valence Bond Theory

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  • Overlap of singly-occupied atomic orbitals on separate atoms- electrons must have opposite spins
  • The overall energy of the bonded atoms must be lower than the energy of separate atoms
24

Hybridization

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  • # of atomic orbitals in = # hybrid orbitals that come out
  • There are lone pairs in hybrid orbitals
25

Atomic Orbitals

Region of space around a nucleus that electron of particular energy should be found

26

Molecular Orbitals

Region of space around the molecule where electrons are likely to be found

  • Have specific energies and hold MAX of 2 electrons
  • # atomic orbitals used = # molecules orbitals formed
  • Can make for complicated pictures
27

2 Way to Combine Atomic Orbitals

  • Can be constructively or destructively
  • Destructive gives electrons density outside nuclei (tend to pull atoms apart)
28

Constructive combination

Gives electrons density between nuclei (tends to attract atoms)

29

Destructive

Gives electrons density outside nuclei (tend to pull atoms apart)

30

Bonding Order Formula

1/2(bonding e- - anti-bonding electrons)

31

What happens to the identity of a substance after a chemical change (chemical reaction)?

Identity of a substance must be different before and after

32

Law of Conservation of Mass

  • Same atoms of same elements before and after, mass shouldn't change
  • OR The number of atoms of each element must be unchanged in a chemical change or reaction
33

Evidence of Chemical Change

  1. Change in color
  2. Change in temperature
  3. Formation of a precipitate (insoluble salt)
  4. Formation of a gas (bubbles)
  5. Dissolving of a solid
34

Types of Reactions

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  1. Combination Reaction
  2. Decomposition Reaction
  3. Single Replacement Reaction
  4. Double Replacement Reaction
  5. Hydrocarbon Combustion Reaction
35

What is the Combustion Analysis of Hydrocarbons used to determine?

It is used to determine the empirical formula.

36

Percent Yield Formula

(Actual Yield / Theoretical Yield) x 100%

37

What is a solution?

Any homogeneous mixture

38

What is an aqueous solution?

Substance dissolved in water

39

What is an Electrolyte?

A substance that produces a solution that conducts electricity

40

What is Nonelectrolyte?

A substance that produces a solution that does not conduct electricity

41

Difference between Electrolyte and Nonelectrolyte

Electrolyte dissociate in solution to produce ions

Ex: NaCl (s) ---> Na+ (aq) + Cl- (aq)

Nonelectrolyte doesn't dissociate in solution

Ex: Sucrose

C12H22O11 (s) ---> C12H22O11 (aq)

42

What are strong Electrolytes?

Electrolytes that dissociate completely

43

Molecular Compounds that are Strong Electrolytes

  • HNO3 (aq)
  • HCl (aq)
  • HBr (aq)
  • HI (aq)
  • H2SO4 (aq)
  • HClO3 (aq)
  • HClO4 (aq)
44

Weak Electrolytes

Dissociate into ions just a bit

45

Nomenclature of acids

  1. Leads with H and ends with (aq) Ways to memorize naming
  • My R ide Has Hydraul ics (For monatomic anion)
  • I Ate Something Icky (For Polyatomic )
  • Spr ite Is Delic ious (For Polyatomic)
46

Precipitation Reactions

  1. Solvent (What there's more of)
  2. Solute (What there's less of)
47

Solubility

Amount of solute that dissolves in a given amount of solvent at a given temperature.

48

What is it called when ionic compounds dissolve, water molecule cluster around cations and anions in predicted ways?

It is called a Solvation or in aqueous solution, Hydration