Download Pb2+ +2I- → PbI2 (s)

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