AP Chemistry Exam Review
Reactions
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Metal and oxygen gas  Metal oxide
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Hydrogen gas is burned  Water
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Solid calcium is placed in oxygen gas Calcium oxide
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Alkali metals and water Metal Hydroxide (maybe split up) + H2 (g) (boom, exothermic)
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Sodium metal placed in water Na+ + OH- + H2 (g)
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Metal oxide and water Metal hydroxide (maybe split up)
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Solid sodium oxide is added to water Na+ + OH-
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Nonmetal oxide and water Acid (maybe split)
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Sulfur dioxide gas is bubbled through water H2SO4
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Solid ammonium carbonate is heated NH3 + CO2 + H2O
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Solid potassium chlorate is heated with a catalyst KCl + O2
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What is the difference between a Bronsted-Lowry acid/base reaction and a Lewis acid/base reaction? Bronsted
lowry acids give H+, Lewis bases give an electron
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Solutions of sodium hydroxide and hydrochloric acid are placed together H+ + OH-  H2O
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Solutions of potassium hydroxide and hydrofluoric acid are placed together  HF + OH-  F- +H3O+
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What is the conjugate base in the reaction above? F-
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Solid sodium carbonate is placed with hydrochloric acid  H+ + Na2CO3  H2O + CO2 + Na+
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Solutions of sodium hydroxide is added to a solution of ammonium nitrate  NH4+ + OH-  NH3 + H2O
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Solutions of silver nitrate is placed with sodium chloride  Ag+ + Cl-  AgCl (s)
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What color is the above reaction? White
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Solutions of lead nitrate is placed with sodium iodide  Pb2+ +2I-  PbI2 (s)
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What color is the above reaction? Yellow
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Solid zinc is placed in a solution of silver nitrate  Zn + 2Ag+  Zn2+ + 2Ag
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Which is oxidized? Zinc
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Which is at the cathode? Silver
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What is the standard cell potential? 1.56 V
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Is it spontaneous? How do you know? Spontaneous, the E is positive
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How many electrons are transferred? 2 electrons
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What was the initially molarity of the solutions? 1M
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List 6 strong acids HCl, HBr, HI, H2SO4, HNO3, HClO4
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List 2 strong bases NaOH, KOH
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What is difference between strong and weak acids? Strong acid dissociate 100%, weak acids do not dissociate
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List the 4 spectator ions that are always spectators in solutions. Alkali Metal ions, NO3-, C2H3O2-, NH4+
Shapes
CH4
H2S
NH3
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What is the shape of each molecule?
Tetrahedral
bent
trigonal pyramidal
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What is the hybridization of each molecule?
sp3
sp3
sp3
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Which has the largest dipole moment?
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What are their bond angles and why?
Largest – H-Boding
109.5°
105°
107°
(decreasing because of more unshared pairs)
SF4
XeF4
BrF5
ClF3
sp3d2
sp3d
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What is the hybridization of each?
sp3d
sp3d2
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What is the shape of each?
seesaw
square planar square pyr.
T-shaped
Bonding
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H2S has a higher boiling point than CO2. Polar/nonpolar
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H2O has a higher boiling point than H2S. Hydrogen bonding/Dipole-dipole
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I2 is a solid whereas F2 is a gas. Both London Dispersion forces. I2 has greater molar mass/# of electrons, more
of a chance of an instantaneous dipole
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NaCl is a solid whereas H2O is a liquid. Ionic/Covalent
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LiF has a higher melting point than CsBr. Both Ionic, Higher Lattice Energy because smaller means more
attraction.
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MgO has a higher melting point than NaF. Both Ionic, Higher Lattice Energy because MgO is +2/-2 which is
more attraction.
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SiO2 is a solid and H2O is a liquid. Covalent network, covalent
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NH3 is soluble in water but not benzene (C6H6). Polar/Nonpolar – like dissolves like/
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What is the difference between polar and nonpolar? Assymetric/Symmetric
Trends
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Li is smaller than Cs. Valence electrons have more attraction to positive nucleus.
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S2- is larger than Cl-. More valence electrons gives more repulsion
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O is smaller than Li. More valence electrons, more protons, more attraction between nucleus and electrons.
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K has a smaller ionization energy than Na. Less energy to remove electron, because valence electrons are further
away from nucleus – less attraction.
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Cs is very reactive in water. Less energy to remove electron, because valence electrons are further away from
nucleus – less attraction.
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B has a lower first ionization energy than Be. B has one electron in p, Be has a full s orbital – less energy to lose
the one in the p
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1st IE = 400, 2nd IE = 800, 3rd IE = 4000, 4th IE = 4500 – what element could this be? Jump in energy is at 2nd
electron, it could be Mg, Be, Ca, Sr, or Br
Descriptive Chemistry
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Why is Fe attracted to a magnet and not Zn. Fe is partially filled d orbital – paramagnetic. Zn is fully filled d
orbital - diamagnetic
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What color is zinc chloride, why? White, fully filled d orbital.
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NO2 does what? Dimerize, double molar mass, bond with itself (oh and its brown)
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SO2 has a bond order of 1.5, why? It has resonance (one single, one double)
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CO2 has two double bonds – how many sigma and pi bonds are there? 2 sigma, 2 pi.
In order – alcohol, amine, ketone, ester, carboxylic acid, ether, aldehyde
Colors
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Na+ yellow
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Cu+2 greenish-blue
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Fe(NO3)2 (aq) orange
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KMnO4 (aq) purple
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AgCl white
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Ag2S black
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PbI2 yellow
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CuCl2 (aq) blue
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NO2 (g) brown
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H2 colorless, whoop or boom in presence of a flame
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N2 colorless, 78% of atmosphere, puts a flame out
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O2 colorless, 21% of atmosphere, ignites a flame
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CO2 colorless, puts out flame
Stoichiometry, Gases, Solutions, and States of Matter
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When can you use 22.4 L/mol? 1 atm, 25°C
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Moles = mass divided by Molar mass
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Grams = Molarity x Volume (L) x Molar Mass
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If given mass or %, how do you find the empirical formula? Divide by molar mass to get into moles, divide by
smallest one to find ratio of moles – that is your empirical formula.
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Equation for any dilution or titration: M1V1 = M2V2
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In a titration, what does that equation find? Equivalence point
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What is the equivalence point? When the moles of acid is equal to the moles of base
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What is the end point? When the color of the solution changes
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What happens when you are half way to the equivalence point? pH = pKa (buffer)
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What are conditions for an ideal gas? High Temp, Low Pressure
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At what conditions does an ideal gas deviate? Low Temp, High Pressure
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What affects the KE of a gas? Absolute Temperature
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What affects the speed of a gas? Temperature and Molar Mass
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What gas effuses the fastest? Lowest Molar Mass
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If given moles and total pressure, how do you find partial pressure? Moles / total moles = Partial Pressure /
Total Pressure
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What is it called when you go from a solid directly to a gas? Sublime
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What happens to the temperature when changing the state of matter? Temperature stays constant, Energy
changing
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What is happened to the molecule when you are changing the state of matter? Breaking intermolecular
attractions, NOT the bonds.
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What happens to the freezing, boiling points, and vapor pressure when you make a solution? BP goes up, FP
goes down, Vapor Pressure goes down
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What are the three equations you use for that solution problem? ΔT = Km
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Which has a higher boiling point in a solution – C6H12O6, NaCl, or Na2SO4. Na2SO4 (3 particles)
m=mol/kg
Mm=mass/mol
Thermochemistry
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If given a list of reactions, what can you do to the reactions and the ΔH? Flip and multiply/divide
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If given Hf or Sf or Gf, what do you do? Sum of products – sum of reactants (multiply by # of moles)
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If given bond energies, what energy goes into breaking bonds? Forming bonds? + energy breaks bonds, - energy
forms bonds
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ΔG = ΔH - T ΔS, what does negative mean for ΔG, ΔH, ΔS? What do you have to make sure of before
calculating? Negative means spontaneous, exothermic, less disorder. Change into Joules
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At equilibrium, what equals 0? ΔG
Kinetics
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What does a catalyst do? Lowers activation energy
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What are four ways to increase the rate of a reaction? Concentration, particle size, catalyst, temperature
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What happens to the rate if you double the concentration in a 0 order reaction? 1st order? 2nd order? Stays the
same at zero order, doubles at first order, quadruples at second order.
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If the reaction is overall 3rd order, what are the units of k? M -2 sec-1
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What is the difference between a catalyst and an intermediate? Catalyst is not in the reaction, intermediate is
formed and then consumed
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What do you graph (starting with concentration and time) on your x and y axis for 1st order to get a linear graph?
2nd order? First order – ln [A] vs t, Second order – 1 / [A] vs t
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What is the half-life equation for a first order reaction? t half-life = 0.693 / k
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What do you graph given k and Temp, to find activation energy? How do you find activation energy? ln k vs 1/T,
Slope = -Ea / R
Electrochemistry
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Losing electrons is = oxidation
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Cathode is where what occurs = reduction
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Reaction you flip is what = oxidation reaction
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Oxidized element is the what agent = reducing agent
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Electrons flow from = anode to cathode
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E° has to be what to be spontaneous positive
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What is the best salt bridge made out of? What if salt bridge is removed? Na+ NO3-, no voltage or no current
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If you add concentration of reactants, what happens to the E°? more spontaneous, E is more positive
Equilibrium
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How do you know you are at equilibrium? The rates of the forward and reverse reaction are the same
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What happens to your K if you reverse the reaction? What happens if you multiply all the coefficients by 2?
Reverse reaction = K-1, double the reaction coefficients = K2
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Kp = Kc (RT)Δn … what is R, T, and Δn stand for? R = 0.0821, T = Temp in K, Δn = change in moles
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If concentration of reactants is added, where does the reaction shift? Toward products
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If heat is added to an exothermic reaction, where does the reaction shift? Toward reactants
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If pressure is increased by decreasing volume of gas, where does the reaction shift? Towards the least number of
moles
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% dissociation = x / Mo x 100%
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pH = - log (H+)
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pH + pOH = 14
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[H+] = 10-pH
HA + H2O ↔ A- + H3O+
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Write equilibrium expression. Ka = [A-][H3O+]/[HA]
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Given Ka and initial Molarity, M, write how to find pH. Ka = x2 / [Mo]
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Given pH and initial Molarity, M, write how to find K. Find H+ then [H+]2/[Mo-H+] = Ka
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Larger the Ka = stronger the acid
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Given grams of NaF and Molarity and Volume of HF, how would you find the pH? What equation would you
use? What is this called? Find molarity of F-, then plug into pH = pKa – log [A-]/[HA], buffer
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Titrations before equivalence point = do a buffer problem where OH- = A- and [HA] is left over acid
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Titrations at equivalence point = flip to a Kb problem and do a x2/Mo of OH-
PbI2 (s) ↔ Pb2+ (aq) + 2 I- (aq)
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Write equilibrium expression. Ksp = [Pb2+][I-]2
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What is the ratio of I- to Pb2+? 2 to 1 ratio
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Given Ksp, how would you find molar solubility? Ksp = 4x3
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Given Molarity of Pb2+, how would you find Ksp? Pb2+ = x so (x) (2x)2 = Ksp
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If Molarity of Pb(NO3)2 (aq) is given with Ksp, how would you find I- concentration? Ksp = (M) (2x)2
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If you removed water, what happens to K? nothing, concentration is independent of volume in Ksp problems
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If NaI (aq) is added, what happens to the Pb2+ concentration? If I- concentration increases, then Pb2+ decreases.
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If given Molarity of Pb2+ and I- and Ksp, what do you do? What can you find out? Do a Q problem, plug in the
numbers and then compare to the Ksp and find if a precipitate occurs.
2 HI (g) ↔ H2 (g) + I2 (g)
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Write the equilibrium expression. Kc = [H2][I2]/[HI]2
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What do you need to know in order to do ICE? Initial molarity and one equilibrium molarity.
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Show ICE to get your K value. Kc = [M at equilibrium]2/[Mo – M at equilibrium]2