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AP Chemistry Exam Tips
Posted by: Dora L.
Date: May 6, 2018
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Date: May 7, 2018
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Top 10 AP Chem Exam Tips

April 25, 2016
Its getting closer to exam week and I'm sure everyone is starting to feel the crunch.  Not to fear, we have the top 10 tips for students; written by our Chemistry Tutor (Dora L.).  Some tips are more AP Chemistry leaning, but you can still apply these excellent strategies to your own AP Subject.  

1. Preparation

a) Bring pencils, pen, eraser, a ruler, and a calculator fully charged to the exam with your Student ID.

b)   Go to bed early the night before to get 8 full hours of sleep.  Sufficient sleep will allow you to think clearly in the exam and perform better.  Have a small breakfast in the morning. 

 2. Understanding a Question

Make sure you clearly understand what the question asks for before attempting to solve it.  Always read the question twice.  Underline the key information and data given.  The data and information are presented in equations, data charts, and graphs to be extracted from. Don’t go off to the wrong tangent.

3.   Solving MC Problems

The re-designed MC exam is about 50% conceptual and 50% on math work.  It tests the student’s ability to
analyze data.  The question is the Stem, while the data/equations/graphs/diagrams are Stimuli.  Take time to analyze the information presented in the Stimuli before making a choice.  There are 4 choices, out of which 2 are totally irrelevant and should be eliminated, while the remaining 2 could be quite close requiring your knowledge and judgment to make the right choice.

4.   Attention to details

a)   Avoid making careless mistakes, such as leaving out a zero when copying down a number.

b)  Pay specific attention to units, such as converting form kJ to J to make units consistent in solving Thermochem problems, or is the Δ H given in kJ/g or kJ/mol?  Is the question asking for the energy of 1 photon or 1 mole of photon?  These can seriously affect the correctness of your answers.

c)  Always include units, significant digits, a descriptor (for you to find the number later on to solve the next step), and box the answers.

d)  Once an answer is calculated, ask yourself, does the number make sense?  An extremely large or small
number may trigger you to re-examine your work for errors.

5.   Conceptual Explanations

a)  In explaining concepts or justifying a statement, such as using intermolecular force to compare boiling points between two molecules, keep your explanations to 4-5 sentences.  There is a tendency that the longer a student writes, the more likely he is going to contradict himself near the end.

b)  When comparing between substances, always describe both to get full credit.  Do not formulate your
answer only based on the description of one substance.

6.   Net-Ionic Equations

When asked to write an equation, pay specific attention to whether the question asks for a molecular equation or net-ionic equation.  If net-ionic equation is expected, writing a molecular equation will not earn a point.

7.   Quantitative Calculations

Show your work.  It is difficult for the Reader to read your mind and try to understand where a number
comes from when it suddenly appears from nowhere, unless you have shown the previous work leading to such a number.

8.   Hand-writing

a)   Number each answer. Always write legibly in larger prints and allowing spaces between questions.  Small prints are very hard on the Reader’s eyes.  You want your Reader to be as fair as possible in grading. 

b)   Don't spend a lot of time erasing wrong answers.  If several lines have to be erased, just cross them out.  It saves time.

9.   Formula Sheet

Be familiar with the Formula Sheet.  It saves time when you can locate a formula quickly.

10. Time Management

a)  Total time allowed to complete 60 MC questions is 90 minutes. Plan 1.5 min per question.

b)  Total time allowed for FRQ is 105 minutess.  Plan approximately 20-24 minutes each for questions 1, 2 and 3 in FRQ section.  Plan 7-8 minutes for short questions 4-7.

c)  If there is time left, always recheck your work for errors made in calculations.  When working under pressure, it is easy to input a wrong number into the calculator to generate a wrong answer.  This is the time to catch your careless mistakes.

 Good Luck!

Our First Blog Post! Helping AP Chemistry Students with Exam Review

April 22, 2016
One of our very own tutors (Dora Lee) has compiled a list of Important topics and concepts to study for the AP Chemistry Exam, split up by topic.  Each section links to Dora's very own YouTube AP Chemistry Videos, just click on the topic to watch the videos.

 1.     Stoichometry and Introductory Concepts (Module 2)

a)    Use of Mass Spectrophotometer to determine average atomic mass of isotopes; interpret mass spectrum         for relative abundance and mass number
b)    Identify limiting reactant and predict mass/moles of products formed
c)    Solve empirical formula, molecular formula and hydrate formula problems
d)    Design a lab procedure to perform gravimetric analysis to determine mass % in a mixture sample
e)    Understand the principles behind paper chromatography, filtration, and distillation and apply techniques to         separate a mixture

2.     Reactions (Module 3)

a)    Differentiate between a strong, weak and non-electrolyte
b)    Classify reactions as precipitation, acid-base, oxidation-reduction, synthesis, decomposition, and complex         ion formation, as well as predicting products of reactions
c)     Apply solubility rules – All salts of group IA, nitrates and ammonium are soluble in water
d)    Write net-ionic equations
e)    Know the techniques to perform titration.  Analyze data to calculate molarity or molar mass of an acid
f)      Assign oxidation numbers
g)    Balance redox reactions by half-reaction method
h)    Recognize spectator ions, excess ions, and precipitates formed in particulate drawing, and calculate            molarities from particulate drawings

3.     Gas Laws (Module 4)

a)    Mathematical relationships and graphical representations of P, V, T and n
b)    Use Ideal Gas Law to solve gas stoichiometry problems
c)    Calculate partial pressures from mole fractions and total pressure
d)    Apply Dalton’s Law in problems of gas collection by water displacement
e)    Relationship between pressure, mole, density, molar mass, temperature, and velocity
f)     Use 4 key postulates in the Kinetic Molecular Theory to account for Ideal Gas behavior
g)    Use pressure and mole relationship to predict empirical formula
h)    Use Maxwell-Baltzmann curve to reason the distribution of gas velocity and kinetic energy

 4.     Atomic Structure & Periodic Trends (Module 5)

a)     Relationship between wavelength, frequency, and energy in the electromagnetic spectrum
b)     Account for the spectrum of hydrogen using the Bohr model
c)     Write electron configurations for atoms and ions following the Aufbau Principle, Hund’s Rule, and Pauli          Exclusion Principle, and recognize paramagnetic and diamagnetic nature of electrons
d)     Use Coulomb’s Law to account for periodic trends in atomic radius, ionization energy, electron affinity, and          electronegativity
e)     Analyze photoelectron spectrum (PES) using binding energy and intensity to identify orbital and number of          core vs valence electrons
f)      Use Ultraviolet-Visible spectrum as an analytical tool to study electronic transitions of an atom, and
        Infrared spectrum to study bond vibrations for identification of molecules

5.     Bonding and Orbital Hybridization (Module 6)

a)    Interpret the potential energy diagram in terms of bond length and bond energy for the interaction between         2 atoms when a covalent bond is formed
b)    Account for the trends of electronegativity and identify bond types
c)    Use the Born-Haber cycle to calculate enthalpy of formation of an ionic compound
d)    Account for relative lattice energy and melting points of ionic solids by use of Coulomb’s Law
e)    Calculate enthalpy of a reaction using bond energy
f)     Draw Lewis structures for molecules that obey the Octet Rule and for those that form expanded octets
g)    Use Formal Charge to choose the most appropriate Lewis structure
h)    Apply VSEPR to predict molecular structure, bond angle, and molecular polarity
i)     Use orbital hybridization to account for molecular geometry


6.     Intermolecular Force and Intramolecular Bonding (Module 7)

a)    Understand the basis of intermolecular forces and use them to account for the relative boiling point,
       enthalpy of vaporization, vapor pressure, and states of matter for polar and non-polar covalent molecular
b)    Use intramolecular bonding in terms of ionic bonding, network covalent bonding, and metallic bonding to
       predict properties of solids
c)    Differentiate between interstitial and substitutional alloys
d)    Differentiate between n-type and p-type semiconductors
e)    Calculate heat energy using temperature change, enthalpy of fusion, and enthalpy of vaporization from a
       heating/cooling curve
f)     Interpret phase diagrams

7.     Solutions (Module 8)

a)    Know the techniques in preparing a solution of given molarity and in making dilution
b)    Identify the 4 types of solute-solvent interaction when a solution is formed and illustrate the interactions
       with particulate drawings
c)    Understand the energy involved in enthalpy of solution

8.     Kinetics (Module 9)

a)    Reason reaction rates using the 4 factors
b)    Determine instantaneous rate from a rate diagram
c)     Determine reaction rate from experimental data table
d)    Write rate laws and calculate the rate constant, k, with units
e)    Know the graphical and linear relationship of concentration vs time in zero, first, and second order
f)     Use reaction mechanism to support rate law, and draw potential energy diagrams for endothermic and
       exothermic reactions, and identifying the activation energy
g)    Draw kinetic energy diagram to illustrate the effect of temperature on reaction rate
h)    Use the collision model to account for successful reaction
i)     The function of a catalyst is to lower the activation energy so the reaction rate is increased.  Differentiate
       between homogenous and heterogenous catalysts
j)     Use Beer’s Law to perform kinetics experiment


9.     Chemical Equilibrium (Module  10)

a)    Understand the conditions of dynamic equilibrium
b)    Write equilibrium constant expressions in terms of concentration and partial pressure
c)    Apply the rules in writing K when a reaction is reversed, coefficient changed, or 2 reactions summed up
d)    Use Q, reaction quotient, to predict direction a system will shift to reach equilibrium
e)    Calculate K from concentrations and pressures
f)     Use ICE method to calculate change in concentration or pressure
g)    Use Le Chatelier’s principle to account for the direction a system will shift as a result of change in
       concentration, pressure, or temperature

10.  Acids & Bases (Module 11)

a)    Differentiate between strong and weak acids, strong and weak bases in terms of degree of ionization in
b)    Use Bronsted-Lowry model to define conjugate acid-base pairs
c)    Ka value defines the strength of an acid
d)    Relate pH values to concentration of hydronium and hydroxide ions in a solution
e)    Autoionization of water is endothermic.   pH value of water depends on temperature
f)     Use Ka or Kb, and the ICE method to calculate pH of a weak acid or a weak base when ionized in water
g)    Follow a set of rules and write net ionic equations to predict the acid-base properties of salt solutions
h)    Use bond energy and electronegativity to reason the relative strength of binary acids and oxyacids


11.  Buffer, Titration Curves, and Indicators (Module 12)

a)    Prepare a buffer solution of desired pH
b)    Calculate pH of a buffer solution using Henderson Hasselbalch equation
c)    Reason the pH changes based on the buffering capacity when strong acid or strong base is added
d)    Perform titrations of strong acid vs strong base, weak acid vs strong base, and weak base vs strong acid
e)    Calculate pH values along each titration curve; identify buffer region, ½ way to the equivalence point, and
       the equivalence point; and predict relative concentration of a weak acid vs its conjugate base
f)     Choose an appropriate indicator for a titration based on its equivalence pH

12.  Solubility Product (Module 13)

a)    Write Ksp expression for a sparingly soluble salt in water
b)    Calculate molar solubility, concentration of ions, and Ksp values, and compare relative solubilites
c)    Reason the increase or decrease in solubility using the common ion effect and Le Chatelier’s principle
d)    Use quotient, Q, to predict if precipitate will form when 2 solutions are mixed
e)    Predict selective precipitation

13.  Thermochemistry (Module 14)

a)    Define system vs surroundings
b)    Define heat and work transferred between system and surroundings
c)    Calculate enthalpy of a reaction from enthalpy of formation
d)    Perform coffee cup calorimetry experiments and calculate quantity of heat and enthalpy of a reaction
e)    Use Hess’s Law to sum up overall enthalpy change from a series of steps
f)     Apply the rules to the value of molar enthalpy change when a reaction is reversed or coefficients changed


14.  Thermodynamics (Module 15)

a)    Gibbs’ Free Energy defines the thermodynamics favorability of a reaction in terms of enthalpy and entropy
b)    Gibbs’ Free Energy, Enthalpy and Entropy are all state functions
c)    Relationship between Gibbs’ Free Energy and equilibrium constant

15.  Electrochemistry (Module 16)

a)    Label a Galvanic cell diagram and understand its operation
b)    Understand the function of a salt bridge
c)    Write half-reactions and overall reaction of a Galvanic cell; calculate standard cell potential
d)    Define relationship between Gibbs’ Free Energy and cell potential and equilibrium constant
e)    Use Le Chatelier’s Principle to account for increase or decrease in cell potential when concentrations are
f)     In an electrolytic cell, reaction is not thermodynamically favorable and requires an energy source (battery)
       to push the electrons
g)    Write half-reactions for the electrolysis of water, molten salt, and aqueous solutions; use reduction or
       oxidation potential to predict products of electrolysis
h)    Use quantitative relationship between moles of electron and metal to calculate mass of metal deposited
       in an electroplating process

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