Spring 2016
Finals Study Guide
AP Chemistry
Made by Ashley Thomas
Table of Contents
Section 1: Acids and Bases
1.1 Titrations
1.2 Indicators
1.3 Buffers
1.4 Solution Preparation
Section 2: Calorimetry
2.1 Specific Heat
2.2 Metals
Section 3: Gases
3.1 Ideal Gas Law
3.2 Gas Stoichiometry
3.3 Limiting Reactant
Section 4: Precipitation Reaction
4.1 Solubility Rules
Section 5: Lab Notes
5.1 Titration Lab
5.2 Are You oKa? Lab
5.3 Resisting Change Lab
5.4 Twice the Titration Lab
5.5 Hottest Lab Ever
5.6 (Don’t) Taste the Rainbow!
5.7 MW by FPD Lab
5.8 Speed of a Reaction
5.9 Qualitative Cation Lab
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AP Chemistry Final Exam Study Guide
ACIDS AND BASES
1.1 TITRATIONS
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Formulas to Know
o pH + pOH = 14
o pH = -log[H+]
o pOH = -log[OH-]
o [OH-]*[H+] = 1*10-14
o n1M1V1 = n2M2V2
o Percent Ionization =
(ionized acid concentration at equilibrium) / (initial concentration of acid)
Strong Acids:
o Hydrochloric Acid
o Hydrobromic Acid
o Hydroiodic Acid
o Nitric Acid
o Sulfuric Acid
o Perchloric Acid
Strong Bases:
o Group 1 Hydroxides
o Group 2 Hydroxides
pH
o acids < 7
o neutral = 7
o bases > 7
Strong Acids and Strong Bases completely ionize in solution
H3O+ = Hydronium
1.2 COMMON INDICATORS
INDICATOR
PHENOLPHTHALEIN
BROMOTHYMOL BLUE
RED LITMUS
BLUE LITMUS
ACID COLOR
Colorless
Yellow
Red
Red
BASE COLOR
Pink/Red
Blue
Blue
Blue
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UNIVERSAL INDICATOR Red/Orange/Yellow
METHYL RED
Red
LITMUS (AZOLITMIN)
Red
Blue/Violet/Purple
Yellow
Blue
You probably don’t need to know these off the top of your head, but it is still good information to
generally know.
1.3 BUFFERS
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Buffer Basics
o Either . . .
Weak Acid and It’s Salt
Weak Base and It’s Salt
o Has the ability to resist change in pH upon the addition of small amounts of acid or base
o
Graph Point Calculations
o Initial pH: ICE chart and Kb or Ka formula
o Point Along Graph: mole chart and Henderson-Hasselbalch Equation
o Half-Equivalence Point:
 pH = pKa
 pOH = pKb
 Henderson-Hasselbalch
 Concentration of Acid/Base = Concentration of Conjugate Base/Acid (respectively)
o Equivalence Point
 Moles of Acid = Moles of Base
 ICE Chart and Kb or Ka formula
o In Excess: mole chart, find new concentration, pH or pOH equation
Henderson-Hasselbalch
[𝐴− ]
o
Acid: 𝑝𝐻 = 𝑝𝑘𝑎 + 𝑙𝑜𝑔 ([𝐻𝐴])
o
Base: 𝑝𝑂𝐻 = 𝑝𝑘𝑏 + 𝑙𝑜𝑔 (
[𝐵𝐻 + ]
)
[𝐵]
Common Ion Effect
o Shift in equilibrium caused by addition of a compound containing an ion in common
with the dissolved substance
o The presence of the excess ions from the dissolved salt greatly inhibits the dissociation
of the acid
o The position of the dissociation equilibrium has been shifted left by the presence of the
ions from the salt
PowerPoint Notes
o Adding a base to Buffer Solution
 Steps
1) Assume the reaction goes to completion and use stoichiometric ratios
YOU MUST CONVERT TO MOLES!!!!
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o
2) Use the original equation to carry out the equilibrium calculations
CONVERT BACK TO MOLARITY!!! Volumes are additive!
Adding an acid to Buffer solution
 Steps
1) Assume the reaction goes to completion and use stoichiometric ratios
MUST CONVERT TO MOLES!!!!
2) Use the original equation to carry out the equilibrium calculations
CONVERT BACK TO MOLARITY!!! Volumes are additive!
 Henderson-Hasselbalch
 The equation is useful for calculation the pH of the solution when the
ratio of [A-] to [HA] is known

o
o
conjugate base
acid
Buffer Solutions with Weak Bases
B + H2 O ↔ BH + + OH −
1) The Weak base reacts with any H+ added
2) And the conjugate acid reacts with any added OHConvert moles back to molarity and insert into the original equation
Alternatively
 We can obtain the Ka value for Ammonium from the given Kb value for NH3
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Formula: pH = pKa + log
Formula: pOH = pKb + log
conjuagte acid
base
Types of Buffer Solutions
o Type 1:
 Combine a weak acid with its conjugate base
 Ex) HF and KF (a basic salt)
o Type 2:
 Combine a weak base with its conjugate acid
 Ex) NH3 and NH4Cl (an acidic salt)
o Remember that NH3 can also be written as NH4OH
o Type 3:
 Add a limited amount of a strong acid with an excess of a weak base. The result
will be the same solution as in type 2
 Ex) add 0.70 moles of HCl to 1.0 Liter of a 2.0 M solution of NH3. This
will result in an excess of 1.30 moles of the base and generating 0.70
moles of the NH4 ion
o Type 4:
 Add a limiting amount of a strong base with an excess of a weak acid. The result
will be the same as in type 1
 Ex) add 0.50 moles of NaOH to 1.0 Liter of a 2.0 M solution of HF. This
will result in an excess of 1.5 moles of the acid and generating 0.50
moles of the F- ion.
o Type 5:
 Prepare a solution of an amphoteric substance
 Ex) 1.0 M solution of NaHCO3
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1.4 SOLUTION PREPARATION
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Titration Lab
Resisting Change Lab
2 CALORIMETRY
2.1 SPECIFIC HEAT
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Definition: The amount of energy required to raise one gram of a substance one degree Celsius
Formula: q=mCp∆T
May need to know:
o qsystem = -qsurroundings
o Temperature is a measure of the average kinetic energy of particles in a substance
o Heat is the sum of all kinetic energy of all the particles in a substance
2.2 METALS
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Every metal has its own specific heat
The identity of a metal can be determined by figuring out the specific heat
3 GASES
3.1 IDEAL GAS LAW
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PV = nRT
o P- pressure
o V- volume
o n- moles
o R- constant
o T- temperature
Variations
o PM = DRT
o PV = (m/M)RT
Ideal Conditions
o 1 atm, 22.4 L, 273 K, 1 mol
o Particles take up no space and no volume
o No IMFs between particles
o Won’t liquefy (no volume)
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3.2 GAS STOICHIOMETRY
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At STP
o One mole of gas has a volume of 22.4 L
Volume to volume under any conditions
o
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𝑉
𝑉
Avogadro’s Law (𝑛1 = 𝑛2 )
1
2
All other stoichiometry
o Use ideal gas law (see page 5)
3.3 LIMITING REACTANT
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Limiting Reactant: a reactant that is completely consumed during the reaction
Excess Reactant: a reactant that remains after a chemical reaction stops
The amount of product that can be formed is ALWAYS determined by the limiting reactant
Adding more of the excess reactant to a reaction won’t affect the reaction because it was
already in excess.
How to Find:
o Convert moles of both reactants to one of the products using dimensional analysis
4 PRECIPITATION REACTION
4.1 SOLUBILITY RULES
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Soluble
o ALL nitrates, acetates, ammonium compounds, and group one salts
o Chlorides, bromides, and iodides EXCEPT silver, lead, and mercury (I)
o Fluorides EXCEPT group 2, lead (II), and iron (II)
o Sulfates EXCEPT calcium, strontium, barium, mercury, lead (II), and silver
Insoluble
o Carbonates and Phosphates EXCEPT group 1 and ammonium
o Hydroxides EXCEPT group 1, strontium, barium, and ammonium
o Sulfides EXCEPT group 1, group 2, and ammonium
o Oxides EXCEPT group 1
5 LABS (FROM AP)
5.1 TITRATION
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Background Information
o Titration: process in which the concentration of a solution is determined by measuring
the volume of that solution needed to react completely with a standard solution of
known volume and concentration
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o Process: gradual addition of standard solution to unknown
o Color change of indicator indicates end point of titration
Indicator used: Phenolphthalein
o Pink when basic
o Colorless when acidic
Procedure
o 25mL of HCl Solution and 1-2 drops of indicator into Erlenmeyer Flask
o Add NaOH gradually until solution changes to light pink
o Record what the buret reading is before and after the titration
Calculations
o Moles of NaOH: multiply concentration by liters used
o Moles of HCl: one to one ratio so it’s the same as NaOH
o Concentration of HCl: moles of HCl divided by liters of HCl
o Average molarity: you should know this one
5.2 ARE YOU OKA?
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Possible Indicators
o Phenolphthalein
 Colorless: 1<pH<8
 Pink: 8<pH<10
 Red: 10<pH<11
o Methyl Red
 Red: 1<pH<5
 Orange: 5<pH<7
 Yellow: 7<pH<11
o Orange IV
 Orange: 1<pH<3
 Peach: 3<pH<5
 Yellow: 5<pH<11
Pre-Lab
o Chemical Equation
o Equilibrium Constant Expression
o pH when [acid]=[conjugate base]
o Choose an indicator: why would phenolphthalein not be a good indicator?
 Half equivalence point is 2.12
5.3 RESISTING CHANGE
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Overview
o IMPORTANT: The Henderson-Hasselbalch equation allows the pH of a BUFFERED
solution to be calculated NOT just a solution from any acid or base reaction
o Remember, whenever H+ or OH- ions are added to a solution you must calculate the new
solution concentrations before you do anything else (mole chart)
How to Prepare a Buffered Solution of a Certain pH and Buffer Capacity
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o
o
Figure out which conjugate acid-base pair to use for given solution
 The most effective buffers have equal concentrations of acid and base
 The pKa of the chosen compound must be within + or – 1 of the desired pH
Calculate the desired concentration of the buffer
 Concentration of components of buffer determine the capacity of the buffer and
thus you must take into account to amount of OH- or H+ that will be added to
the solution
5.4 TWICE THE TITRATION
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Indicators
o Methyl Orange (pKa= 3.40): Red (1-3) Transition (3-4) Yellow (5-13)
o Methyl Red (pKa= 4.95): Red (1-4) Transition (4-6) Yellow (6-13)
o Phenolphthalein (pKa= 9.40): Colorless (1-8) Transition (8-10) Red (10-13)
o Bromothymol Blue (pKa=7.10): Yellow (1-6) Transition (6-8) Blue (8-13)
o Phenolphthalein (pKa= 10.00): Colorless (1-9) Transition (9-11) Blue (11-13)
Lab Tips
o LABEL EVERYTHING!!! = helps keep track of solutions
o Always rinse glassware with DISTILLED or DEIONIZED water
Basic Graphs
o Weak Acid with Strong Base
o
Weak Base with Strong Acid
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o
Strong Acid/ Strong Base
5.5 HOTTEST LAB EVER
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Background
o Hess’s Law: if the same overall reaction is achieved in a series of steps, rather than one
step, the enthalpy change for the overall reaction is equal to the sum of the enthalpy
changes for each step in the reaction series
Post-lab calculations
o Mass of solution: assume density is the same as that of water (if not explicitly stated),
then convert straight from volume to mass
o Mass of Reactants (solid and liquid): add mass of solid to calculated mass of liquid
o Change in Temperature: T(final) – T(initial)
o Heat (see page 5- calorimetry)
o Moles of solid reactant: molar mass
o Enthalpy change: q/moles
o Average Enthalpy change: average the trials
5.6 (DON’T) TASTE THE RAINBOW [AFTER AP EXAM]
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Pre-Lab Calculations
o Molarity of diluted vinegar: M1V1=M2V2
o Molarity of household vinegar: same as dilute
o Percent by mass: (molarity (mol/L)  milliliters  molar mass density)*100
 Should end with all units canceling
5.7 MW BY FPD [AFTER AP EXAM]
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Freezing Point Lab
Effect of Unknown on Lauric Acid Freezing Point
o Little bit of unknown = little lower
o More unknown = even lower
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5.8 SPEED OF A REACTION [AFTER AP EXAM]
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Reaction Order Graphs
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Pre-Lab Information
o Sensor used to measure concentration of color over time: colorimeter
Know how to do all of the calculations in a graphing calculator
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5.9 QUALITATIVE CATION LAB [AFTER AP EXAM]
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Washing Precipitates
o Why? Remove free floating ions from the precipitate
o How
 1-2 mL of distilled water (unless another chemical is specified)
 Stir
 Centrifuge (15-20 seconds)
 Discard wash water (but be careful to not drain the precipitate until told to do so
in lab instructions)
My Tips
o Keep track of which solution is in which beaker (labels – in pencil – are extremely
helpful)
o Know what exactly you are looking for when testing the unknown: use the procedure in
addition to detailed notes taken throughout the initial experiment
 The results from testing the unknown may not exactly match your experiment but
as long as they fit in with the procedural descriptions you should be good to go
o DON’T SECOND GUESS YOURSELF!!!
 If you are sure you saw a precipitate then there is something there, even if it looks
a little funky, in that case (if you have time) redo the trial just in case
o NOTES! Taking detailed notes on observations throughout the experiment is very
helpful, be it on an extra sheet of paper or directly on the lab, they will help you figure
out if the ion really is there
o DON’T SKIP STEPS!
 Yes, you have to make sure is silver, no one cares if you are positive that it’s silver
if you haven’t conducted an experiment that confirms that it is in fact silver.
o Don’t rush! Take your time and be extra careful, this is after all the final exam.
GOOD LUCK!! MAY THE RESULTS OF THE LABS BE EVER IN YOUR FAVOR! AND MAY THE FORCE BE WITH YOU!
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