Ultimate Chemistry Guide

The Ultimate Chemistry Guide

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How to Study THE3PMETHOD

STEP 1: PLAN

You need to plan for two time periods. The month and the week. Have a general idea of what you have upcoming for the next 4 weeks so you can plan for any upcoming exams, projects and papers. For the upcoming week you should have a study schedule planned out for all of your courses. Be sure to include both instructional studying and studying via practice.

STEP 2: PRE-STUDY

You absolutely need to study material before your instructor actually goes over it. As crazy as it may sound you'll be blown away by just how much it helps you. Find a good resource that helps you prestudy your material. You'll have questions prepared for your instructor, you can get clarification and the content will be solidified.

STEP 3: PRACTICE

Do not approach practice blindly. You should know what types of questions you need to practice and practice over a period of time. The two largest mistakes I see students make is only practicing a topic once and using your notes to practice. This is how students believe they know it but then flunk their exam. You should be practicing the same material at regular intervals using spaced repetition and active recall. Two scientifically backed principles.

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Acid & Base dissociation,

Kinetics : Rate laws, Integrated, Graphing

Kinetics: Arrhenius Equation & plot

Heating Curve, Calorimetry

Enthalpy, Gibbs Free Energy

Entropy

Spontaneity

Redox Reactions + acidic or basic solution

Electrochemistry

Nuclear Chemistry

Atomic Structure

Tips: notice how frequency is in both equations. You can replace frequency with c divided by wavelength

Average atomic mass from isotope abundance

Ion Charge

Elements with less than 4 electrons tend to lose them and elements with more than 4 electrons tend to gain them. It's all about trying to get to a stabalized filled shell.

Most calculations call for Kelvin. If you're not American you likely will not see degrees Fahrenheit. We just like to make things more complicated over here.

Electrons & EM Spectrum

Tips: notice how frequency is in both equations You can replace frequency with c divided by wavelength

Principle (distance from nucleus)

Angular momentum (shape of orbital)

Magnetic (orientation) -l, -1, 0, 1, ,l

Spin (orientation of electron spin) +1/2 or -1/2

Compounds

Tips: notice how frequency is in both equations. You can replace frequency with c divided by wavelength

Naming Ionic Compounds

Tips: Ionic compounds are made up of metals (positive ions) and nonmetals (negative ions) or polyatomic ions.

x a m p l e s

Common Polyatomic Ions

Anions and corresponding oxyacid.

Common Polyatomic Ions

Positive (cation) polyatomic ions

Common Monatomic Anions

Ion Charges

Positive (cation) polyatomic ions

How to determine the charge on a transition metal from formula:

Covalent/Molecular Compounds

Electron Configuration

Exceptions: Cr & Cu have excited 4s electrons which fill the 3d orbitals and make the atoms more stable.

Noble gas notation:

Start with the noble gas in the previous row. You do not need to write electron configuration for any electrons prior to the noble gas. Write electron configuration for electrons after the noble gas up to the element you are doing.

PTABLE.COM has an electron setting and you can check your electron configuration for any element.

Quantum Numbers are located on page 4

Lone pairs take up more room than single pairs do so you'll notice that bond angles are less for those with lone pairs.

Formal Charge

Find the formal charge of each atom in the molecule. A molecular structure in which all formal charges are zero is preferable to one in which some formal charges are not zero.

14 S T E M W I T H K R I S T E N . C O M

Weusemolecularorbitaltheorytodeterminehowmanyelectronsareinbondingvsantibondingand thusthestabilityofthemolecule.

Antibondingorbitals=theattractiveforcebetweenthetwonucleiandelectronsrepeleachother Bondingorbitals:Addingelectronstotheseorbitalscreatesanattractiveforcethatholdsthetwonucleitogether.

Twofillmolecularorbitals:

writetheelectronenergydiagramforeachatomonthemolecule.

Molecular Orbital Theory Bond Order

Usingmolecularorbitaltheory

Chemical Reactions

ClassifyingReactionTypes:

Activity Series

Used for Single Replacement Reactions

The higher up on the activity series an element is the more reactive it is. If an element is above another it can replace it in a single-displacement reaction. Example Ca is above Mg, so Ca would replace Mg but Mg would not replace Ca Metals can replace other metals and halogens can replace other halogens

Metals (+ Ions)

More reactive

Halogens(- Ions)

Less reactive

Conversion Factors

Converting between moles & grams

Conversion Factor:

1 Mole OR

molar mass

How to find molar mass:

molar mass

1 Mole

example 1: conversion factor for MgO

1 Mole

40.31 g MgO

molar mass of MgO from periodic table

Mg (24.31) + O (16.00) = 40.31 g

Add up all the masses (from the periodic table) of each element in the molecule Don't forget to count for multiples of the same element.

Example: CO (carbon dioxide) would be C (12.01g) + O 2x (16.00g)= 44.01 g CO

Converting between atoms/molecules & moles

When converting between atoms/molecules and moles we use Avagadros number (6 022x10^23) which states that 6 022x10^23 particles (atoms or molecules) is equal to 1 mole of that substance

So 1mole=6.022x10^23particles.

1 Mole

6.022 x 10

IMPORTANT:AVAGADROS#NEVERCHANGES!

6.022 x 10

1 Mole OR

The Mole ratio is used to convert between one compound to another You get the ratio via the coefficients (the numbers in front) of each compound.

Moles A OR

In the example reaction, if we wanted to convert from Al to Cu we would look at the coefficients in front of those There are 2 Al's for every 3 Cu's so the conversion factor is:

Conversion Factors Continued:

Converting between moles & grams

Conversion Factor:

1 Mole

molar mass

OR molar mass

1 Mole

How to find molar mass:

example 1: conversion factor for MgO

1 Mole

40.31 g MgO

molar mass of MgO from periodic table

Mg (24.31) + O (16.00) = 40.31 g

Add up all the masses (from the periodic table) of each element in the molecule. Don't forget to count for multiples of the same element.

Example: CO (carbon dioxide) would be C (12.01g) + O 2x (16.00g)= 44.01 g CO

Converting between atoms/molecules & moles

When converting between atoms/molecules and moles we use Avagadros number (6.022x10^23) which states that 6.022x10^23 particles (atoms or molecules) is equal to 1 mole of that substance.

So 1 mole = 6.022 x 10^23 particles .

1 Mole

6.022 x 10

IMPORTANT: AVAGADRO'S # NEVER CHANGES!

6.022 x 10

1 Mole OR

grams A

___g A

1 Mole A

Volume A

Moles A

moles A moles B

Mole Ratio

1 Mole B

Volume B

Moles B

1 Mole A g A

grams B

6 022 x 10^23 atoms

1 Mole A

Atoms A

1 Mole A 6.022 x 10^23 atoms

moles B

moles A

6.022 x 10^23 atoms

1 Mole A

Atoms B

1 Mole B 6.022 x 10^23 atoms

g B

1 Mole B

Stoichiometry

Includes: moles, molecules, molarity, volume

Atoms

/molecules A

MolarityA

Moles/Liters

Mass A

molar mass

avagadros #

Moles A

22

VolumeGasA

.4mL=1mole   atstp

MolarityB

Moles/Liters

Mole Ratio

Moles A

Moles B

molar mass avagadros #

Mass B

Atoms

22.4mL= 1mole  atstp

VolumeGasB

/molecules B

Limiting Reactant, % Yield, % Error

The liming reactant is the reactant that limits the amount of product that is produced.

A + B ---> C

If we have 5 moles of A and 6 moles of B, A would be the limiting reactant because it would only allow us to produce .5 moles of C with excess B.

STEPS TO FIND LIMITING REACTANT & THEORETICAL YIELD

Step 1: Using the information you have been given for the reactants (the amount of moles or grams) calculate the amount of product that would be produced from each reactant using stoichiometry.

Whichever reactant produces the least number of grams is your LIMITING REACTANT/reagent.

Your theoretical yield would be the number of grams of the product that your limiting reagent would produce.

If reactant A produces 56 g of C and reactant B produces 64g of C. The limiting reactant would be A and the theoretical yield would be 56g.

PERCENT YIELD

Actual Yield: The amount you actually produced in the lab or what the question tells you that someone else produced.

Theoretical Yield: You get this from finding the amount produced by the limiting reagent (see above) It is the amount of product (grams) produced by your limiting reagent

Actual Yield

% Yield = x 100%

Theoretical Yield

Tip: You can calculate % yield with moles too. Both the actual yield and theoretical yield have to be in moles one can't be moles and the other be grams

Solubility

No reaction : if one of the reactants is insoluble. A Precipitate will form: if both reactants are soluble, but one of the products is not soluble.

Soluble Exceptions

Group 1 ( Li, Na, K..)

None, Always soluble

Halides (Cl, Br, I) Ag, Hg, Pb

Ammonium

Nitrate

Bicarbonates

Chlorates

None, Always soluble

None, Always soluble

None, Always soluble

None, Always soluble

Sulfates Ag, Ca, Sr, Ba, Hg, Pb

Insoluble Exceptions

Carbonates Group 1 & Ammonium

Chromates Group 1 & Ammonium

Phosphates Group 1 & Ammonium

Sulfides Group 1 & Ammonium

Sulfides Group 1 & Ammonium

Hydroxides Group 1 & Ammonium + Ba

Notice how group 1 and ammonium are exceptions to all insoluble compounds, that is because they are always soluble. So for the most part you can assume something is insoluble if its not in the soluble table, except BaOH.

Empirical & Molecular Formulas

Percent composition isthe percent by mass of an atom in a molecule.

Empirical Formula Molecular Formula

Lowest ratio of each element in the molecule

Actual number of atoms of each element in the molecule

Pressure Conversions

Gases

Ideal gas law

STP (Standard Temperature & Pressure)

Pressure = 1atm

Temperature = 273 K

@ STP 1 mole of gas = 22.4 L

Partial Pressuresthe partial pressures of each gas add up to the total pressure.

Partial pressure can be found using the mole fraction of a gas:

You can get all of these (below) by setting ideal gas law to R and cancelling out values that are constant.

Used when not in ideal conditions (college or AP level only)

Gases Continued

Rate of Effusion

Tip: Therateofeffusionisperunitoftime.Misthemolarmassofeachgas.

Ifitsaysonegaseffusesxtimesfasterthantheotherthanxwouldbethevalueforthefaster gasandfortheother.

Average Kinetic Energy

Tip: When determining which R value to use, look at the units of the other items in your equaiton and what units you want as the output. We have temperature as an input (Kelvin) and we want kinetic energy (Joules/mol) as the output. Thus we would use the R value with J/mol * K.

R = 8.3145 J/mol*k

Root-Mean Square Velocity

Tip: When determining which R value to use, look at the units of the other items in your equaiton and what units you want as the output. We have temperature as an input (Kelvin) and moles as imputes. We want velocity which is in m/s.. Thus we would use the R value with J/mol * K, as joules can be converted to Kg * m^2/s^2

R = 8.3145 (Kg*m^2/s^2)/mol*k

Solutions & Colligative Properties

CONCENTRATION UNITS

HENRY'S LAW

The amount of gas dissolved in solution is proportional to the pressure of the gas above the solution.

HEAT OF SOLUTION

Solutions & Colligative Properties Continued

RAOULT'S LAW

BOILING POINT ELEVATION

A nonvolatile solute raises the boiling point of a solution.

FREEZING POINT DEPRESSION

A nonvolatile solute lowers the freezing point of a solution.

OSMOTIC PRESSURE

Not ionic or a strong acid/base : Ionic compound or strong/acid base: determine how many ions it would produce.

MgCl2 would dissociate into 1 Magnesium Ion and 2 Chloride ions, giving you 3 total ions:

Acids and Bases

ACID BASE NEUTRALIZATION REACTION

An acid-base neutralization reaction produces water and a salt (ionic compound)

STRONG ACIDS AND BASES

Dissociate completely Strong electrolytes

STRONG ACIDS

WEAK ACIDS AND BASES

Do not dissociate completely weak electrolytes

STRONG BASES

If it is not a strong acid or base you can mostly assume it is weak.

ACID STRENGTH TREND: BINARY ACIDS

Increases as you go from left to right on the periodic table and down.

HF< HCl < HBr < HI

ACID STRENGTH TREND: OXYACIDS

Increases as the electronegativity of the central atom increases and increase with the number of oxygens present.

Acid strength depends on the stability of the ion (conjugate base) after dissociation. A more electronegative element or more oxygens will help the stability of extra electrons.

EQUILIBRIUM

Tips: Remember that Q (the reaction quotient) is the same expression but with current concentrations/pressures K represents the concentrations at equilibrium

Equilibrium (Concentration)

Equilibrium (Pressure )

Convert between Kp and Kc :

For gases:

Relationship between Q & K:

Q is current concentrations K is concentrations at equilibrium.

Q < K towards products

Q > K towards reactants

K<1 Favors Reactants

K > 1 Favors products

Q > Ksp Forms precipitate

Q< Ksp Does not form precipitate

Percent ionization/dissociation :

EQUILIBRIUM CONTINUED. LE' CHATELIER'S PRINCPLE

STRESS SHIFT Reason

Increase Concentration

Away from substance (other side)

The system will use up the excess substance If you increase the conc of a reactant more product will be produced If you increase the concentration of a product, more reactant will be produced

Decrease Concentration

Towards Substance (same side)

The system will need to generate more of the substance to reestablish equilibrium.If you decrease the concentration of a reactant more reactant will be produced. If you decrease the concentration of a product the product will be produced.

Increase Pressure OR decrease in Volume

Towards fewer gas molecules (count the coefficients of the gases)

With increase pressure or decreased volume, gas molecules are more likely to collide and produce the side of the reaction with less gas molecules

Decrease Pressure OR Increase in Volume

Towards higher moles of gas (count coefficients of the gases)

With decreased pressure or increase in volume the reaction favors the side with more gas molecules.

Increase Temperature

Away from heat

Endothermic - towards products

Exothermic- towards reactants

Towards heat

The reaction will use up the extra heat, thus going away from the heat.

Decrease Temperature

Addition of Catalyst

Endothermic- towards reactants

Exothermic- towards products

The reaction will compensate by going towards the side of the reaction that will produce heat.

No adjustment to equilibrium

A catalyst only speeds up the rate of a reaction, it does not cause a change in equilibrium.

Tips: Strong acids and bases will dissociate completely , so assume that your H + and OH concentrations are equal to the Initial acid base concentrations. For weak acids and bases use an ICE table and the Ka and Kb values.

Weak acid dissociation example:

Equilibrium (Acid disassociation)

Equilibrium (Base disassociation)

Quadratic formula is used when x is not negligible

Tips: Kw value changes at different temperatures but in general use the value given to the right

Henderson -Hasselbalch

Use when you have a conjugate acid and base pair present

Ionization constants: Use the ionization constants given in your course textbook or reference manual.

Kinetics Part 1 : Rate Laws

For most questions a=1. Most courses give you reactions in 1 molar so a would not matter.

Zero Order

Slope =-k t

first Order

Slope =-k t

second Order

Slope = k t

Tips:

The rate does not depend on concentration.

This is the only rate order that the graph will be a straight line for concentration vs. time. Half life is dependent on concentration

The half life for a first order is consistent. It will be the SAME each time. If 10 minutes it will stay 10 minutes. It does not depend on concentration.

The half life for a 2nd order will double each time. This means if it is not consistent it is likely a second order reaction. The k value does not change !

concentration values can be percents, mass (g) or molarity values!

If the graph is not straight, look at the half lives to determine the reaction order. 1st order will be constant, 2nd order will double.

Kinetics Part 2: Arrhenius Equation

Use this version when you have one reaction

k= rate constant

A= frequency/pre-exponential factor

e = the number e

R= gas constant

T= temperature in Kelvin

Ea= activation energy

Use this version when you you have reactions at two different temperatures. Be sure to put the first and second temperatures and k values in the correct places.

Heating Curve

When in the phases the temperature changes but it does not during the phase change itself.

CALORIMETRY

Thermo

evaporating/ condensing

CONSTANT PRESSURE / COFFEE CUP CALORIMETRY

CONSTANT VOLUME/ BOMB CALORIMETRY

Usetheheatcapacityofthecalorimeter.

Formulas

Solid, Liquid or gas phase:

Melting or Freezing:

Evaporating or Condensing:

C(specificheat) andDeltaHare specifictothe substance

Common question hint:

If they ask the final temperature of a mixture of water with two different temperatures. Set qwater =-qwater. Then solve for Tf, they both will have the same final temperature.

34 S T E M W I T H K R I S T E N . C O M

Thermo

CALCULATING ENTHALPY

From standard enthalpy's of formation: From bond energy:

Hess' Law:

Reactions who addup to your overall reaction can be combined to produce the enthalpy of the reaction.

GIBBS FREE ENERGY

used to measure the maximum amount of work done in a thermodynamic system when the temperature and pressure are kept constant

= 0 at equilibrium

At Standard conditions

At Standard conditions + equilbrium

Solve for K

Of the reactions current conditions

Relationship between G and K

Important:

Some courses use log instead of ln and/or the shortned version of the above equations. Make sure you are using the correct values for the equation your course is using!

Thermo ENTROPY

Entropy is the level of disorder.

Increasing Entropy: Solid (low), Liquid (medium), gas (high)

Microstates are the number of different possible arrangements of molecular position and kinetic energy at a particular thermodynamic state.

Thermo SPONTANEITY

Reactions are spontaneous with G < 0 (negative)

You can plug in values to find the sign and magnitude of G. Which will tell you if it is spontaneous

If we plug in signs to the above equation, we can determine at what temperatures the reaction will be spontaneous.

Redox Reactions

OXIDATION NUMBR RULES

OIL RIG

Oxidation Is Losing electrons.

Reduction Is Gaining electrons.

0 +2 +2 o

Zn was oxidized, it lost 2 electrons

Cu2+ was reduced, it gained 2 electrons

BALANCING REDOX REACTIONS IN ACIDIC AND BASIC SOLUTION

1 Divide the reaction into half reactions and balance any elements that aren't H and O.

2 Balance O atoms with water

3 Balance the H atoms by adding H+

4 Balance the charges by adding electrons (e-) Add OH- ions to BOTH SIDES to neutralize H+

5 Add the half reactions and simplify Multiply the reactions if needed in order to cancel out electrons from both reactions

6

Combine H+ and OH- to make H2O

cancel out excess H2O that is on both sides

Balance charges by adding e-

Add half reactions and simplify Multiply reactions if needed to achieve same number of electrons in each reaction

FAT CAT

Electrons Flow from the Anode To the CAThode.

Galvanic/ Voltaic Cell

Ecell = Positive (+)

Spontaneous Reaction

Anode = Negative (-)

Cathode= Positive (+)

Doesn't require external voltage

Ecell from cell potentials

Electrolytic Cell

Ecell = Negative (-)

Non-spontaneous Reaction

Anode = Positive (+)

Cathode= Negative (-)

Requires external voltage

Ecell (standard) from K

Your course either uses the log or ln version. Make sure you use the correct value for it.

Ecell from Q

Your course either uses the log or ln version. Make sure you use the correct value for it.

Gibbs Free Energy

Electrical Charge

Nuclear Chemistry

TYPES OF PARTICELS & EQUATIONS

Gamma Decay/Emission

Beta Decay/Emission

Element does not change. Atomic number and mass number stay the same.

Positron Emission

Element changes. Atomic number decreases by 1, mass number stays the same.

Electron Capture

Element changes. Atomic number decreases by 1, mass number stays the same.

Element Changes. Increase atomic number by 1

Alpha Decay/ Emission

Element Changes. Atomic number decreases by 2, mass number decreases by 4.

Radioactive decay is a first order reaction (for more info on first order reactions see kinetics section)

Protons Neutrons # of stable nuclei and relative stability