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š§ŖAp Chemistry š§Ŗ
Test date: Tuesday, May 6 2025.
8:00 Am Local
Section 1: Multiple Choice (MCQ) 50%
60 questions
90 minutes
Section 2: Free Response (FRQ) 50%
7 questions: 3 long FRQs, worth 10
points each 4 short FRQs,
worth 4 points each
Unit 0: Basics of Chemistry
Unit 1: Atomic Structure and Properties
Unit 2: Compound structures and
properties Unit 3: Properties of
substances and mixtures Unit 4:
Chemical Reactions
Unit 5: Kinetics
Unit 6: Thermochemistry
Unit 7: Equilibrium
Unit 8: Acids and
Bases
Unit 9: Thermodynamics and Electrochemistry
Unit 0: Basics of Chemistry
Significant Figures
Sig Figs: the accuracy of an answer to a mathematical problem
- Numbers known to be exact Rules
- All non-zeros are significant 2.34 all 3 sig figs
- Leading zeroes are not significant 0.00 23 2 sig figs
- Zeros between digits are significant 320098 6 sig figs
- Trailing zeros arenāt significant 25000 2 sig figs
- Unless there is a decimal point 25000. 5 sig figs We know exactly 2 and some. We can guess about 2.2 It looks about less than half 2.2 is 2 sig figs We know exactly 2.3 and some. We guess about 2. 2.35 is 3 sig figs When calculating: To add/sub use the lowest number of sig figs in all numbers, round for others. To multiply/divide calculate normally, then round the answer to lowest sig figs in.
Picket Fences
- Create picket fence, usually 3 columns
- Write known amount
- Create conversion factors, end with desired unit
- Units should cancel out to desired
- Multiply top, divide by bottom.
Ionic Compounds:
- Cations go first, anions second.
- Cations are + ions, Anions are -
- Change to -ide, unless polyatomic ions Potassium Sulfide
- Donāt need to capitalize unless beginning of sentence
Transition metals:
- Use charges in the name, written by roman numerals CuF 2 Copper and Fluoride Cu2-^ F^1 + [opposite of swap and drop] Copper(ll) Fluorine
Covalent Compounds:
For 2 nonmetals 1- mono 2- di 3- tri First element as normal, write out whole name 4- tetra 5- penta 6- hexa Write second, add -ide at the end 7- hepta 8- octa 9- nona Use prefix for number of atoms, 1st and 2nd Element Donāt put mono for first element
Polyatomic Ions
Group of ions that act as a single unit and have their own charge Written with parenthesis () There are many, just remember the ones listed above.
DONāT FORGET THE CHARGE
Also Mercury: HgāĀ²āŗ Peroxide: O22- Bromate: B 2 O- Iodate: IO3- Sulfide: S2-
4 3
Solubility Rules
Soluble in water: All Alkali metals. K+, Na
, Li
All CH 3 HOO
- . NO - , NH - Most Halides. Cl
, Br-, I-^ except Pb^2
, Ag
, Hg
Most sulfates. SO 2-^ except Ca^2
, Ba^2
, Pb^2
, Sr^2
Not soluble in water: Most Phosphates. PO 4 3- (^) Except Na+, K+, NH 4
, CaS Most Carbonates. CO 3 2- Except Na
, K
, NH 4
, CaS Most Sulfides. S2-^ Except Na
, K
, NH 4
, CaS Most Hydroxides. OH- Except Na
, K
, Ca^2
, Ba^2
(atomic mass 1 )(% abundance 2 ) + (atomic mass 2 )(% abundance 2 )
= Average
Avogadros
6.022 x 1023 6.022 x 1023 particles in 1 mol of a substance Conversion factor for particles to moles 1 mol = 6.022 x 1023 particles
Mass Spectroscopy of Elements
Isotopes:
Same element but has different number of neutrons. Same protons, same electrons. Same element, but have different masses.
A = # of protons+ # of Neutrons
mass # - Atomic # = # of neutrons
Will have different Amu # Atomic weights are an average mass of isotopes and their relative abundance Average atomic Mass: atomic mass
Mass Spectroscopy:
As many spikes as there are isotopes If need to solve, % abundance given Mass spectroscopy allows us to find:
of isotopes. 35 Cl
(^37) Cl atomic # of isotopes 35 and 37 relative amount of isotope 75% and 25%
of spikes = # of isotopes, relative to
number at base Height = relative abundance in %
Average atomic mass:
(same as above) Mass on graph, abundance given or look up
Avg mass of Cl = (35)(0.757) + (37)(0.242) = 35.
Mass of cl = about 35. (Includes smaller isotopes)
Pure Substances
- Substance containing only 1 element or compound. Matter with a fixed composition and properties. Usually element or compound.
Law of definite proportions:
Compounds with the same elements and proportions are the same compounds Percent composition: percent by mass of each element in a compound
- Find molar mass of compound. C 2 H 6 2(12.01( + 6(1.01) = 10.08 g/mol
- Calculate the mass of the component of the compound For C. 2(12.01) = 24.01 g C
- Find the percentage of the component 24.01 / 30.08 = 0.798 = 79.98% C % = (molar mass of element)(# of moles of element) (total molar mass of compound) H 2 O: ( 1.008)(2) į„ 18.01 = 0.11 = 11% Hydrogen (16) (1) į„ 18.01 = 0.89 = 89% Oxygen
Atomic Structure
Atom: made of protons (+), neutrons (no charge), and electrons (-)
Electrons weigh almost nothing, most mass in the nucleus of protons and neutrons. As the number of electrons increases, so does the repulsion between them.
Electron configuration:
Describes the arrangements of electrons and electron shells Core electrons- inner electrons Valence electrons- electrons on the outermost shell Each shell has orbitals. more electrons, more orbitals filled. 1st shell: 1s orbital 2nd shell: 2s and 3p 3rd shell: 3s and 3p Start at lowest, fill then move up. Make sure each has double. Each arrow is an electron. There are 2 in every orbital. Sublevel must fill before next.
Energy levels:
Electrons want to stay as far away from each other, spread into energy levels, orbitals
Energy level: Possible shapes
electrons
1 S 2
2 S P 8 (2 + 6)
3 S P D 18
S: P:
D:
Written configurations:
(shell#)(orbital name)#e-(shell#)(orbital name)#e- Energy level is the family on ptable. Based on element location, and number of electrons. Lithium , 3 e-, 2 electrons in 1s, 1 more for 2s: 1sĀ²2sĀ¹ Scandium, 21 e-. 2 in 1s, 2 in 2s, 6 in 2p, 2 in 3s, 6 in 3p, 2 in 4s, 1 in 3d. 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^1 [Ar]4s^2 3d^1 Based on noble gas configuration
Photoelectron spectroscopy
Measures the amount of energy needed to remove an electron from a shell Basically same as mass spec, but with orbitals instead of isotopes
Coulomb's law:
Tells strength of interaction between charges, depends on distance and magnitude Greater distance, less force between nucleus and electrons Smaller distance, more force between nucleus and electrons Force of electrons increases right, decreases down. Known as electron affinity. F has most, Cs has least
Z-effective/ Effective nuclear charge:
Atomic number - # of shielding e- E- attracted to nucleus, repelled by other electrons Farther from nucleus, less āpullā. Closer to nucleus, more āpullā Shielding effect: other e- in the way, shielding by other e- Zeff = z - s Z = atomic number. S = number of shielding e-
Photoelectron Spectroscopy:
Used to measure the relative energies of electrons in atoms or molecules. Photoelectric effect is the emission or ejection of electrons, usually a metal. Called photoionization. Analyze peaks which are each sublevel to show binding energy of electrons
Periodic Trends
Atomic Radius:
Increase down, decrease right Electrons outside, less pull to nucleus
- Cations always smaller than parent, lose e-, more pull for inside
- Anions always bigger than parent, gain e-, less pull to inside As zeffective increases, atomic radius decreases With more pull towards the nucleus, electrons shrink in and radius decreases
Coulombic attraction
Negetive e- and positive p+ are attracted towards
each other. Bigger radius, less pull, easier to remove
Effective nuclear charge: net+ charged experienced by valence electrons
Ionization energy:
First ionization energy: amount of energy required to remove the first electron Second ionization energy: amount of energy required to remove second electron Decrease as move down, more energy higher column of ptable Increase as move right, less energy left side of ptable
- Radius decreases as move up and right, more energy
- Farther from nucleus, easier to remove When all valence electrons are gone, the next increase in energy is a lot. Has to pull from a lot closer to the nucleus.
Unit 2: Compound Structures
Chemical Bonds
Electronegativity:
Ability of an atom to attract shared electrons. Often associated with Coulomb's
- Attractive force between particles increases as charge increases
- Attractive force decreases as distance increases
Bond types:
Covalent bonds Ionic bonds non-polar polar -ionic- Share of electrons equal unequal Transfer bond-dipole none partial pos/neg: +/- electronegativity Less than .05 0.5 - 1.7 More than 1. Visual e- share A--------B A--------B A : B Visual Polar, non-polar, ionic bonds compare the electro-negativity difference.
Ionic Compounds:
Transfer of electrons from element to another Bonds are stronger when charges are larger and ions smaller; coulomb's law
- Lattice of crystals
- High melting point, high boiling point
- Hard and brittle
- Good insulators
- Can conduct electricity when liquid or aqueous
Metallic Bonding:
Metallic atoms, same or different, combine to be pure or allows Metallic cations attracted to delocalized sea of valence electrons Intermolecular forces are stronger with smaller cations and more VE
- Shiny & malleable
- Conduct heat and electricity
- Oxides are ionic and basic
Covalent bonds:
Bonds 2 non-metals and share valence electrons to fill both shells. polar or nonpolar. Single, double, or triple bonds
- Not shiny but colorful
- Brittle, can be hard or soft
- Poor conductors
- Form ions
- Oxides are acidic and covalent
Oxides:
Metal oxides: Non-metal oxides Chemical component with metal and at least 1 oxygen atom Basic pH, 7+ Ionic compounds Makes salts with acid Oxide components with nonmetal elements Acidic pH, 7- Covalent compounds Makes salts with bases
Interstitial alloys:
Smaller electrons fit into space between larger atoms to bond Atoms are very different sizes, from different sides of ptable
Substitutional alloys:
Equal size electrons create evenly distributed sea of atoms Replaces atoms and relocate
Lewis Diagrams
Show the distribution of valence electrons in covalent bonds Lone pairs: pair of valence electrons that donāt bond to anything, but still contribute to shape Atoms can form single, double, triple bonds, must be in pairs of 2
How to draw:
- Determine # of valence electrons in each atom
- Write element with most possible bonds in the middle a. Usually carbon, 4, or the weird ones like sulfur, 5
- Draw other elements around
- Connect electrons and bonds to each element a. Each bond line is 2 electrons
- Fill valence shells with lone pairs, usually 4 or 2 Hydrogen can only have 1 bond and 0 lone pairs
Resonance and formal charge
When there are multiple options for lewis structure, formal charge determines structure
Formal charge:
#ve - (lone e- + e- to bonds)
Ideally should be 0. If not, lowest charge is best Total number of valence electrons - bonded and lone pairs
Resonance:
Some arrangements are equally valid, but a bond is moved, or lone pair on different element Double arrows used to show
Octet exceptions:
Most atoms need 8 electrons to be stable. But there are some exceptions
- Helium and hydrogen both only need 3 electrons
- Boron only needs 6 Molecules with d subshells can have more than 8 electrons. Less than 12
- Silicon, phosphorus, sulfur, and chlorine can expand.
- Noble gases can sometimes as well.
VSEPR and bond Hybridization
Predicts the molecular geometry of electrons in elements and compounds Shape of molecule is determined by lone pairs and the bonds of the central atom in a molecule Electrons repel each other, want to be as far away from others as possible Double, triple bonds repulse more than single bonds All angles always add up to 180 on fiat plane, 360 on full
