ap chemistry study guide (part 3 of 3) - amazon s3s3.amazonaws.com/cramster-resource/104049_part 3...

AP Chemistry Study Guide (Part 3 of 3)

Chapter 16 - Spontaneity, Entropy, and Free Energy This is basically picking up even more Thermochem which is good because that means this will be a short chapter. There's just a few more equations relating gibbs-free energy to equilibrium. Equations (New and Old) Relationship Between ΔG° and ΔG This is very simple, when at equilibrium ΔG will equal 0. If you can remember all the way back to thermochemistry, whenever the ΔG was negative, the reaction was spontaneous and favored the forward reaction. When ΔG was positive, it was nonspontaneous and favored the reverse reaction. So, logically, if it equals 0, it will be at equilibrium. If we use the equation: ° and we are told the system is at equilibrium, we can plug 0 in for ΔG and get 0 ΔG° RTlnK, which can simplify into the other new equation: ° ln We can change the Q to K because the system is at equilibrium.

Chapter 17 - Electrochemistry Basics Electrochemistry is directly related to Redox reactions and the activity series chart It is the study of electron transferring between the half reactions It "shockingly" results in electricity Will need the Standard Reduction Potential chart Values are given with 1M concentrations, 25°C, and 1atm Values are for REDUCTION ONLY, to find oxidation reverse the sign Electrochemical reactions will convert energy to electricity if spontaneous Electrochemical reactions will absorb electricity and convert it to energy if nonspontaneous Typically we are asked to find the Standard Reduction Potential (E°) Galvanic Cells (Cell Diagram) Cell voltage = electromotive force (emf) = cell potential They all mean the same thing Voltage - The difference in charge between the anode and cathode Written in a very specific format: Metal (anode) | Ion (anode)(Molarity) || Ion (cathode)(Molarity) | Metal (cathode) Oxidation Connector Reduction Catalysts are placed at the end

Old Equations New Equations H°rxn = ° roducts ° Reactants

S°rxn = S° ° ° ln G°rxn = G° roducts G° Reactants ° G = H - T S

What's the difference between ΔG and ΔG°? ΔG° stands for the free energy of the reaction with the reactants and products in their standard state (standard conditions) ΔG stands for the absolute free energy of the reaction, where the reactants and products are not in their standard state (conditions are given)

Standard Reduction Potential (SRP) Chart There are 2 simple rules when looking at this chart: 1.) Coefficients don't affect the voltage 2.) The chart is for reduction only, you must flip the sign of the voltage to find the value for oxidation Trend: The more positive the value, the more easily oxidized that reaction is. More negative...more easily reduced If the sign of the cell voltage is negative, it is nonspontaneous only for the direction it is written in

AP Chemistry Study Guide (Part 3 of 3) Calculating Voltage From a Picture I will be efficient here and just toss 3 things in together: A picture, writing the cell diagram, and calculating voltage off the SRP chart. I will be following through with the reaction on the right.

Connectors In electrochemistry, 2 beakers with 2 different solutions can be connected by a porous disk (left) or salt bridge (right). The porous disk will allow the 2 solutions to interact between themselves and balance the charges until electrons flow. The salt bridge contains a salt whose ions will not affect the other ions in the solutions. The ultimate purpose of these connectors is to balance the charges that way electrons can flow. As we can see, the ions of the salt from the salt bridge distributed themselves into the 2 solutions creating a charged balanced reaction, permitting the flow of electrons. We will also need to be able to figure out what the anode and what the cathode is for this diagram. The zinc will be the anode because it goes from its natural state which has an oxidation number of 0 to a solution where it's oxidation number is +2 The copper will be the cathode because it began as solution and had an oxidation number of +2 and when the electron flow began, it became solid (its natural state) and got an oxidation number of 0 Note that over time, the zinc anode (the light pink stick) will lose mass and the other side where the cathode is will have a zinc plating With this knowledge we can then write the cell diagram: Zn0

(s) | Zn+2(aq) || Cu+2

(aq) | Cu0(s)

Then we can also calculate the cell voltage because we know the oxidation reaction is: Zn Zn+2 + 2e- And the reduction reaction is: Cu+2 + 2e- Cu -(-.76V) + .34V = 1.10V The negative in front of the (-.76V) is just another way of remembering to flip the sign for oxidation

AP Chemistry Study Guide (Part 3 of 3) Spontaneity Table

ΔG° K E°cell Reaction (Standard Conditions)

- >1 + Spontaneous 0 =1 0 Equilibrium + <1 - Nonspontaneous

We can conclude a lot from this table. If we find a ΔG° value that is negative, the K should be greater than one, the cell charge should be positive, and the reaction should be spontaneous under standard conditions. If we find a ΔG° value that is positive, the K should be less than one, the cell charge should negative, and the reaction should be nonspontaneous under standard conditions. If we find a ΔG° value that is 0, the K should be equal to one, the cell charge should be 0, and the reaction should be at equilibrium under standard conditions. The Nernst Equation The purpose of this equation is to show the cell voltage of a reaction not at standard conditions. The voltage using the SRP chart is only for standard conditions. It is important to remember that sometimes, the standard condition charges and the charge using the Nernst equation can sometimes make very little of a difference, or a major difference. It can sometimes make the difference between whether or not the reaction is spontaneous or not. So this brings us to the LAST equation in AP Chemistry: ° ° Let us also recall the thermochem equation: ° ln So we can set them equal to each other in order to derive the Nernst equation: ° = ln

°

° .

, 00

° . 0

° . 0

°

. 0

Actual Equation: ° .

Application Say we have the reaction: Cd(s) + Fe+2

(aq) Fe(s) + Cd+2(aq)

And the concentrations of Fe+2 is .60M, and Cd+2 is .010M Step 1.) Write the oxidation/reduction half reactions Step 2.) Calculate the SRP voltage for the overall reaction (E°cell) Step 3.) Apply the Nernst equation Step 4.) Calculate the voltage for the reaction with non SRP calculations (Solve)

Nernst Values F = Faraday's Constant = 96,500 J/(Vmole) = 96,500 coul/mole Joules per Volt is a unit of charge and simplifies to a coulomb (coul) n = The number of electrons transferred in the reaction (whole number) R = Gas law constant (8.31 J/moleK)

Log vs Natural Log (ln) It really doesn't matter what one you use, they will come out to the same answer. The conversion from ln --> log is 2.303 x ln = log The reason they give both log and ln is because back in the day when calculators weren't so advanced as they are now, they only had the log button.

AP Chemistry Study Guide (Part 3 of 3) Step 1.) Oxidation: Cd(s) Cd+2

(aq) + 2e- Reduction: Fe+2

(aq) + 2e- Fe(s) Step 2.) E°cell = -(-.40V) + (-.44V) = -.04V

Step 3/4.) .0 .

ln

.

. )

.0 . 0 .0 .0 .05V .0 Batteries It's good to get a general idea of how batteries work. The chemistry definition of a battery is several electrochemical cells are connected in a series with a positive and negative end. When we charge a battery, we force the electrons in the opposite direction, which means the voltage backwards must be greater than the voltage forwards. Dry Cell or Leclanché Cell These cells are your everyday battery. AA, AAA, C, D, etc.

Mercury Batteries These cells are used in watches, pagers, photography, hearing aids, etc.

Note that the voltage at standard conditions made the reaction appear to be nonspontaneous (negative voltage), but once the Nernst Equation is applied, we can see that with different concentrations the reaction will be spontaneous (positive voltage). This is an example of where the Nernst Equation can change spontaneity.

Role of the Stuff Inside The moist paste will act as a supersaturated solution to keep the electron flow moving. This is that white crap that you sometimes see leaking from the battery. Do not confuse it for acid. The graphite is representative of a salt bridge in which the electrons will transfer from the anode to the cathode without being attracted to anything else because it is nonpolar. Anode: Zn(s) Zn+2

(aq) + 2e-

Cathode: 2NH4+

(aq) + 2MnO2(s) + 2e- Mn2O3(s) + 2NH3(aq) + H2O(l) Zn(s) + 2NH4

+(aq) +2MnO2(s) Zn+2

(aq) + Mn2O3(s) + 2NH3(aq) + H2O(l)

Role of the Stuff Inside The basic medium solution of KOH and Zn(OH)2 keeps the electron flow going. The steel is acting the same way as the graphite does in the dry cell Anode: Zn(Hg) + 2OH-

(aq) ZnO(s) + H2O(l) + 2e- Cathode: HgO(s) + H2O(l) + 2e- Hg(l) + 2OH-

(aq) Zn(Hg) + HgO(s) ZnO(s) + Hg(l) The Zn(Hg) is a solution, but is not aqueous

AP Chemistry Study Guide (Part 3 of 3) Lead Storage Batteries These are the batteries used in cars

Fuel Cell Hybrid car batteries

Role of the Stuff Inside

The H2SO4(aq) is the solution that will allow the electron flow to keep moving.

Don't mess with this stuff, it is full strength 18 molar acid and will instantly give you a second degree burn

Anode: Pb(s) + SO4-2

(aq) PbSO4(s) + 2e-

Cathode: PbO2(s) + 4H+(aq) + SO4

-2(aq) + 2e- PbSO4(s) + 2H2O(l)

Pb(s) + PbO2(s) + 2SO4-2

(aq) + 4H+(aq) 2PbSO4(s) + 2H2O(l)

Role of the Stuff Inside Process: Oxygen is going to enter from the air, and H2 gas is simultaneously fueling the batter. The anode is the Hydrogen which will diffuse, and some protons of the Hydrogen will also transfer through the proton exchange membrane. When the protons are transferred the charge is balanced and the electron flow will occur, fueling the overall cell. Any hydrogen molecules that aren't transferred will be re-circulated as fuel until they are. The oxygen will continue filtering as heat or as air with water vapor attached. Anode: 2H2(g) + 4OH-

(aq) 4H2O(l) + 4e-

Cathode: O2(g) + 2H2O(l) + 4e- 4OH-(aq)

2H2(g) + O2(g) 2H2O(l)

AP Chemistry Study Guide (Part 3 of 3) Solid State Lithium Batteries They are used in laptop batteries, iPods, portable DVD players, pacemakers, etc.

Electrolysis This is the process where we force a nonspontaneous electrochemical reaction to occur This is very systematic: Application How much Ca will be produced in an electrolytic cell of molten CaCl2 if a current of .452A is passed through the cell for 1.5 hours. Step 1.) Anode: 2Cl-

(l) Cl2(g) + 2e- Cathode: Ca+2

(l) + 2e- Ca(s)

Step . . oulombs

.

00

, 00

Just a quick note: In Physics, an Ampere is 1 Coulomb/second

Step . .0 0.0

. 0

Role of the Stuff Inside

Anode: Li(s) Li+(aq) + e-

Cathode: TiS2(s) + e- TiS2-

Li(s) + TiS2(s) Li+(aq) + TiS2

-(aq)

The separator allows for the balance of charges and keeps the electron flow going. These are special batteries because they are made of Lithium. If you remember the Activity Series chart, it is the highest which means it is the most easily oxidized/produces the most negative voltage. They can produce up to 3V.

Steps to Electrolysis Step 1.) Write the half reactions Step 2.) Multiply your current (amperes) by time (in seconds) to get your charge in coulombs Step 3.) Multiply by your moles of electrons to get the moles of the substance reduced/oxidized Step 4.) Multiply by the periodic mass


Half Life Calculations:

.

k = A rate of decay constant, dependent dddupon the isotope Nt = The number of nuclei at a certain time N0 = The initial number of nuclei .693 = ln2

Chapter 18 - Nuclear Chemistry

Basics Nuclear Chemistry - The study of nuclear reactions and their uses Radioactivity - When the nuclei of an atom change spontaneously and emit energy Nucleons - The stuff inside the nucleus (Protons and neutrons) Mass number - Number of nucleons Atomic number - Number of protons Neutrons - Mass number - Atomic number Isotope - An element with the same number of protons, but different number of neutrons Half life - The time required for 1/2 of any given quantity of a substance to change (react or decay) Fusion - 2 small nuclei join to form 1 large nucleus Fission - 1 large nucleus splits into 2 or more smaller nuclei Why Nuclei are Unstable Electromagnetic forces (Proton repulsion; long range) start to overpower the strong forces (neutron to proton attraction; short range) More neutrons than there are protons Nuclear Trends Elements 1-26 will undergo fusion to become more like 56Fe Elements >26 will undergo fission to become more like 56Fe 56Fe is the most stable element thermodynamically Certain numbers of neutrons and protons are already stable (Magic numbers): Nuclei with an even number of protons or neutrons are more stable than nuclei with an odd number of protons or neutrons All nuclei containing more than 84 protons are unstable or radioactive Isotopes There is more than one isotope for the same element -Each isotope will be distinguished by its mass numbers Different isotopes have different natural abundances Every isotope has a half-life Half-lives are not affected by temperature, pressure, or chemical composition Natural radioisotopes tend to have a longer half-life than unnatural radioisotopes -Radioisotopes is just another word for a radioactive isotope

Naturally occurring can be used to determine the age of a sample Process is known as radioactive dating

Magic Numbers Protons: 2, 8, 20, 28, 50, and 82 Neutrons: 2, 8, 20, 28, 50, 82, and 126

b would be stable because it has 82 protons and 126 neutrons

208 - 82 = 126 neutrons MUST have both a magic number from protons and magic number from neutrons to be stable

AP Chemistry Study Guide (Part 3 of 3) Types of Radioactive Decay

Property Alpha Beta Gamma

Composition

e

Mass 4 0 0 Penetrating Power Piece of paper Aluminum foil 2x4

wood Lead + 12ft of

concrete

Even though there are masses and charges of 0, we still write them to ensure conservation of nucleons Subatomic particles can undergo decay also:

Property Β emission Positron annihilation

Positron emission Electron capture

Equation

n --->

p +

e

e +

e ---> 2

p --->

n +

e

p +

e --->

n

Alpha particles contain 2 protons and 2 neutrons which is represented as a Helium atom Beta particles compose of a broken neutron, which breaks into a proton and an electron Gamma particles don't contribute to a change in mass, charge, or atomic number -Strictly energy, and very strong Band of Stability A band/belt of stability deviates from a 1:1 neutron to proton ratio for high atomic masses

Synthesis of Nuclei Stable nuclei can be converted to other nuclei that are either stable or unstable through radioactive decay Process requires a LOT of energy

The salmon shaded region is the belt of stability Each dot represents an isotope Imagine the belt expanding further to and have a vertical line through the point where protons = 83 Anything to the right of that line is considered above the band. Anything to the left of that line is considered below the band Isotopes above the band will typically undergo alpha radiation (Protons and neutrons will decrease in steps of 2) Isotopes below the band will typically undergo beta emission or electron capture Keep in mind that the magic numbers will cause that isotope to be stable Trend: More neutrons will be required as the nucleus size increases.


Binding Energy Binding energy is the energy required to overcome the repulsion of protons Represented as Eb Existence of binding energy is evidence that mass can be converted to energy Tells whether energy is going to be released if we split a nucleus (fission) or combine two nuclei (fusion) If binding energy increases, then energy is released

Eb = (M(Z protons) + M(N neutrons)) - M(nucleus)

Example

p

n --->

(Deutreium)

1.007825 + 1.00865 2.01410 m 2.016475 - 2.01410 = -.00239 g/mole (mass is not conserved) (-2.39 x 10-6 kg/mole)(3.00 x 108 m/s) = -2.15 x 1011 J/mole

Eb = 2.15 x 108 kJ/mole

Eb per nucleon = .

. . = 1.06 x 108 kJ/mole per nucleon

Nuclear Stability 238U undergoes alpha decay at first to get to 234Th Note the protons and neutrons decreases ssssssssby 2 accounting for the mass difference of 4 234Th undergoes beta emission to get back to the original element but as a different isotope 234U undergoes alpha decay several times to 214Pb in order achieve a place under the band of stability 214Pb undergoes beta emission to 214Po because 214Pb is an unstable form of lead Goes to Po, because that was the previous aaaaaaaaelement before obtaining a spot within the aaaaaaaaband of stability 214Po undergoes alpha decay in order to go to 210Pb which is again unstable 210Pb undergoes beta emission to 210Po because 210Pb is an unstable form of lead 210Po undergoes alpha decay in order to finally achieve a stable form of lead 206Pb

Given: values for proton and neutron Changed grams to kilograms because:

1J = kg m2/s2 Convert into kJ because we are dealing with large amounts Large E means large amount of energy is released (exothermic) Eb is very positive which means lots of energy is saved through stabilization


Chapter 22 - Organic Chemistry Basics To be organic, it must have carbon There are many different kinds of organic molecules: Alkanes, Alkenes, Alkynes, Ammines, Alcohols, Ethers, Esters, Aldehydes, Ketones, Amides, etc. We will specifically look at alkanes, alkenes, and alkynes. These molecules can also attach to other molecules known as substituents. Substituents can either be another specific organic carbon group, or a halogen. Nomenclature There is no easy way to say this, but this is basically all memorization. And it's not so easy either. Let's start off nice and easy. The prefixes will be nearly the same as the Greek prefixes with a few differences:

Now, let's get a little more complex and add the substituent nomenclature. Remember that these will either be carbon groups or halogens. If it is a carbon group, it will end in -yl. If it is a halogen, it will cut off the -ine and attach an -o.

Halogen Fluoro Chloro Bromo

Iodo If for some reason it helps, think of these as Frodo's cousins. Okay, let's kick it up a notch and venture into the wonderful world of alkanes. Alkanes First off, these will ONLY HAVE SINGLE BONDS between then Carbon and Hydrogen They will end in -ane The formula is: CNH2N+2 Some basic properties of alkanes are that they have a low melting/boiling point, nonpolar, and are saturated Let's practice those new prefixes, so we can see a very basic alkane with nothing attached. Methane: Ethane: Propane:

Butane:

Before going into more complex stuff, let's take a look at another form of alkanes, cycloalkanes.

Prefix Number Prefix Number Meth- 1 Hex- 6 Eth- 2 Hept- 7

Prop- 3 Oct- 8 But- 4 Non- 9

Pent- 5 Dec- 10

Carbon Group Compound Methyl CH3 Ethyl CH3CH2

Propyl CH3CH2CH2

Notice how there are only single bonds between the C's and H's. Also notice how they are all nonpolar, and how the carbon chains continuously grow more and more as the prefix gets higher.

Substituents

Carbon groups cannot attach to the

ends of a carbon chain, halogens can

AP Chemistry Study Guide (Part 3 of 3) Cycloalkanes These are represented as polygons of some sort. The carbon chains will not be in a straight line. No cycloalkane exist if there is a prefix of 1 or 2 because it does not produce a polygon.

This picture basically sums it up: The corner points are represented as carbons, and single bonded H's will be attached to those carbons. The most important thing to remember is that cyclobutane benzene. Cyclobutane is all single bonds, benzene is single AND double bonded. The formula for these are CNH2N Alkanes Continued Okay, let's kick it up another notch, we are going to attach stuff to the alkanes now. By adding a halogen or carbon group to an alkane, it will change all of its properties. It will no longer be nonpolar and the melting and boiling point will change; however, it will still be saturated because it has all single bonds. Let's take a look at 3-ethylpentane (I'll explain that number later). So first, we would see pentane (C5H12). Then we would look at the number 3 and know that ethyl is attached to the 3rd carbon in the carbon chain. So it would look like this:

Carbon Numbering So basically, the carbon numbers will be numbered according to whatever carbon the closest carbon group or halogen is attached to. The lowest number carbon will have the substituent attached. For this molecule, it won't really matter because it is in the middle, and either way you number the carbons, it will land on 3. Hypothetically, let's say that the Ethyl was attached to the carbon to the left or right. Then it would change to 2-ethylpentane. If it were moved left, we would label the carbons using the bottom numbers, if we moved it right, we would label the carbons using the top numbers. This numbering is only for alkanes...alkenes and alkynes will be different. But before we do that we can kick it up yet another notch.

AP Chemistry Study Guide (Part 3 of 3) Oh Snap, 2 Numbers! What if we get something like: 2, 2-dimethylbutane...

Well this is just for if the substituent is the same, now we can see what it will look like without the same substituent. It is quite logical, but still requires some thought. Say we have 2-ethyl, 3-methylbutane Butane: Longest carbon chain containing 4 carbons 2-ethyl: Ethyl attached to the 2nd carbon 3-methyl: Methyl attached to the 3rd carbon

But wait! There's more! (Isomers) We're not done yet. In organic chemistry, we get to take a look at isomers. Isomers give the same molecular formula but have a different structure. So looking back at alkanes we had 2 types: Straight chain alkanes, where all the carbons were connected in a row Branched chain alkanes, where carbons are branching from a row of carbons So let's look at a few isomers.

2 Numbers First we should look and see butane which means the longest carbon chain will have 4 carbons. Next, we would see the 2, 2 which means that there are 2 substituents attached to the 2nd carbon. They can either be the same substituent or different. In this case they are the same substituent (Methyl) and because there are 2 of them we will use the other Greek prefix, Di- to make it dimethyl. We use the carbon set of Greek prefixes (Meth-, Eth-, Prop-, But-) to describe the carbon chain, and the substituent. We only use the other set of Greek prefixes (di-, tri-, tetra-, etc) to describe how many substituents are attached So say there was an additional methyl attached to this butane. It would become: 2, 2, 3-trimethylbutane

Relation Between Substituents and the Carbon Number

There is really only one main reason why we must label what

Carbon the substituent(s) is/are attached to...properties.

We should know that different substituents attached to the

same molecule will have a different melting/boiling point

(i.e. 3-ethylpentane vs. 3-methylpentane)

However, what we might not know is that the order in which

those substituents are attached make a difference in the

physical properties as well.

Let's take a look back at the 2, 2-dimethylbutane. According to Wikipedia it has a melting point of -98.8 °C and a boiling point of 49.73°C. Yet if we shift a methyl over to make it 2, 3-dimethylbutane the melting point is -128°C and the boiling point is 57.9°C

AP Chemistry Study Guide (Part 3 of 3) C4H10 Butane or 2-methylpropane? Butane: 2-methylpropane:

On the exam, it is fair game if they ask you to draw the isomers of an alkane, that is if they toss an organic FRQ at you. So just for kicks, let's do 1 more. C5H12

Isomers and Alkanes Remember that carbon groups cannot attach to the ends of a carbon chain. For alkanes, it will always start with the original structure with all the carbons in a row. Now we just pretend that the end of the carbon row is a methyl group that will just trade spots with an H in the middle.

AP Chemistry Study Guide (Part 3 of 3) The longer the carbon chain, the more isomers there will be for the structure. The first 3 alkanes (Methane, Ethane, and Propane) all have 1 isomer, which is their normal structure. We can try to create another structure for them, but it won't happen.

Alkane # of Isomers Alkane # of Isomers CH4 1 C6H14 5 C2H6 1 C7H16 9 C3H8 1 C8H18 18 C4H10 2 C9H20 35 C5H12 3 C10H22 75

Now we can finally move away from alkanes, and go to alkenes and alkynes. Alkanes and Alkynes These are relatively the same thing with a few minor/major differences. Alkenes - Double bonded Alkenes - CNH2N Alkenes - sp2 hybridized Alkenes: -ene Alkynes - Triple bonded Alkynes - CNH2N-2 Alkynes - sp hybridized Alkynes: -yne They are both unsaturated because of their double/triple bonds. This allows for that bond to be broken up more and allow more things to attach to it. Once there are no more double/triple bonds, it will be considered an alkane and saturated. A number must be added to indicate where the double or triple bond is located. The numbering on the carbons is a little different for alkenes/alkynes, than they were for alkanes. They will be ordered according to the closest double/triple bond. We will always want to double/triple bond to have the lowest number carbon. So let's take a look at a simple alkene C5H10 1-Pentene:

Just like alkanes, alkenes have isomers too. Let's look at one for the structure we just made, pentene. One of them would be called: 2-methylbut-1-ene Looks confusing, but let's split it up into what we know. 2-methyl: A methyl carbon group is attached to the second carbon in the longest carbon chain but: The longest carbon chain will contain 4 carbons 1-ene: We haven't seen this before but all it says is that in order to make it an alkene, we need a double bond, which is what that "1" is for. It tells us that the double bond will be located at the first carbon in the longest carbon chain. SO, the structure should look something like this.

Notice that the carbons are labeled starting closer to the double bond so that it will have the lowest number carbon. It is important to know that the double bond is attached to C1 not C2. If it were attached to C2, it would be between C2 and C3 Also notice that because of the double bond, we prevent 1 Hydrogen from bonding with C1 and another from bonding from C2.

Structural Formulas This is rather unrelated to alkenes/alkynes, but will be helpful when trying to write some equations involving these organic compounds. In organic chemistry, we want to show correctness, and to show that in the formulas, we write it according to bonding. Take acetic acid for example: CH3COOH. We don't call it C2H3O2 because it doesn't show how the bonds are ordered. So let's relate it to the structure to the left. We could write it as C5H10 but that leaves several possibilities as to how it is bonded. If we want to write the formula, it would be from left to right: CH2=C(CH3)CH2CH3 We would rarely have to write the structural formula; however, it helps when we start adding halogens, or other things to compounds.

AP Chemistry Study Guide (Part 3 of 3) Acetylene This is important because even though it looks like an alkene, it is really an alkyne. The formula is C2H2 which looks like...

The formation of acetylene has a positive ΔG Additional Alkane Information The larger the alkane, the higher the boiling point is The larger the alkane, the more London Dispersion Forces it has They are the building blocks of everything because they cannot be broken down any further Addition Reactions of Alkenes Some addition reactions include the process where we add a halogen, hydrogen halides (Hydrogen attached to a halogen), or pure hydrogen (hydrogenation) to an alkene, to produce an alkane. Let's take a look at an alkene with just pure hydrogen added. C2H4 + H2 C2H6 or CH2=CH2 + H2 CH3CH3

The unsaturated alkene, C2H4 will break the double bond of the carbon to allow room for the H2 to bond to it, forming a saturated alkane, C2H6. Now for an alkene with a halogen added. C2H4 + Br2 BrC2H4Br or CH2=CH2 + Br2 BrCH2CH2Br

When a halogen is added, the double bond will break and both the carbons will share a bond with one of the bromines, and the other bromine will turn into bromide. Then one of the carbons will take the bromine completely, leaving an open bond on the other carbon, in which the bromide ion will bond, creating the resulting product. Finally, an alkene with a hydrogen halide added. C2H4 + HCl CH3CH2Cl

AP Chemistry Study Guide (Part 3 of 3) The problem with adding hydrogen halides to an alkene is that when the alkene is unsymmetrical, there is more than just 1 potential product. So let's look at an example. C3H6 + HCl CH3CH2CH2Cl C3H6 + HCl CH3CH(Cl)CH3 Notice that they will both balance out,, and we don't know what one will form. This brings us to Markovnikov's Rule. The only good thing about this is that there are a lot of pictures.

So now we know that the reaction of C3H6 and HCl will produce the second reaction because we can see the second carbon has the most substituents attached and will have Cl bond there. Just for kicks we will take a look at 2 Anti-Markovnikov reactions, one with hydro-boration oxidation, and one with radical addition of HBr. Hydro-boration oxidation: Step 1.) CH2=CHCH3 + BH3 CH(BH2)CH2CH3 BH3 is added to an alkene, in which an H from BH3 and the B will bond to the newly formed alkane in a cis-like meaning, they will both be on the same side.

Markovnikov's Rule His rule applies to reactions involving a an unsymmetrical reagent (in this case a hydrogen halide) is added to an unsymmetrical double bond. It states that the halide will bond to the carbon with the most carbon group substituents attached. So, if we look back at our example, the 2nd reaction would be favored according to Markonikov's rule because the carbon in the CH has 2 methyl's attached to it (2 substituents). Any other carbon only has 1 substituent attached to it.

Anti-Markovnikov's Rule This is exactly what it sounds like. This applies to those reactions that don't follow his rule. So hypothetically, if the 1st reaction was favored, then it would be considered anti-Markovnikov because the halide is attached to a carbon with a lesser amount of substituents than another carbon in the same compound. Some reactions that would be considered anti-Markovnikov would be hydro-boration oxidation and radical addition of HBr. Hydro-boration oxidation: This is a 2 step reaction involving BH3 and a peroxide to break the double bond of an alkene into a neutral alcohol. Radical: This is when we add a substance with an unpaired electron. For HBr, hydrogen peroxide MUST be present.

AP Chemistry Study Guide (Part 3 of 3) Step 2.) CH(BH2)CHCH3 + HO2

- CH2(BOH2OH-)CH2CH3 A peroxide ion, HOO-, is added to make the B an ion.

Step 3.) CH2(BOH2OH-)CH2CH3 CH2(OBH2)CH2CH3 + OH- The Carbon bonded to the B will grab the closest O, in which the C-B bond will break, but still remain intact with the molecule through the newly formed C-O bond. The remaining OH- is displaced.

Step 4.) CH2(OBH2)CH2CH3

+ H2O CH3CH2CH2OH (propanol) Water is added where the oxygen from the water reacts with the B in BH2 and a H from the water reacts with the O in the molecule to form a hydroxide within the molecule...A neutral alcohol.

Radical Addition of HBr Fortunately, this is easier than the hydro-boration oxidation reaction. As I said before, hydrogen peroxide must be present in order for this reaction to occur, because it will become quite unstable if we heat it and take the H+ from the HBr, leaving us with the bromide radical. Step 1.) H2O2 + heat 2OH- OH- + HBr H2O + Br -

AP Chemistry Study Guide (Part 3 of 3) Step 2.) CH2=CHCH3 + Br - BrCH2CHCH3

- The Br will attach itself to the carbon with the fewest amount of substituents because when the double bond is broken, a carbon radical forms. And a carbon radical is more stable when it is at a carbon with more substituents attached. In this case, the carbon radical that formed happens to be the carbon with the most substituents attached. This means it is the most stable compared to if a different carbon was made the radical. Obviously, if it was a more complex molecule, the carbon radical could be somewhere else. If the Bromine attached itself to the carbon that is supposed to be the radical, a more unstable radical would form at the end, which won't happen.

Step 3.) BrCH2CHCH3

- + HBr BrCH2CH2CH3 + Br -

The newly formed compound will react with the HBr, this time taking the H+ (just like the hydroxide did in step 1), which will attach itself to the most stable carbon radical, creating propyl bromide and a bromide ion.

Advanced Nomenclature When 2 or more substituents are attached, we can be even more specific when naming the molecule. Especially when it comes to naming the isomers. For example, let's look at a form of 2-pentene. 2-Pentene:

Exceptions to Radical Addition

Both HCl and HI will not be anti-Markovnikov because in the process of the radical reaction, there will be a

step that is endothermic, which means the reaction will be unfavorable.

Cis- vs. Trans- Put simply, cis- is when the Hydrogens attached to the double bonded carbons are on the same side, and trans is when they are on opposite sides. The left structure would be cis-2-pentene because the Hydrogens attached to C2 and C3 are on the same side The right structure would be trans-2-pentene because the Hydrogens attached to the C2 and C3 are on the same side

AP Chemistry Study Guide (Part 3 of 3) We can also be more specific when it comes to the specific structure of a molecule Depending on the structure, we can give them a prefix of: n-, iso-, sec-, tert-. neo- or c- n- is the normal structure c- structure in a cyclical form iso- structure containing an iso unit sec- structure containing a sec unit tert- structure containing a tert unit neo- structure containing a neo unit Here are some examples involving the carbon group substituents

Example 2-methypentane or isohexane

Cycloalkenes CNH2N-2 These are just like cycloalkanes, represented by polygons. The only difference is that there will be an additional line at parts of the polygon in order to represent a double bond. The double bond is assumed to be at carbon number 1 They are assumed to be cis

Exceptions to the Longest Chain Rule

Well, obviously these are the exceptions. If you see an iso, sec,

tert, or neo unit in the structure, you may ignore the longest

chain rule and account for all the carbons in the structure, as

seen to the left. We would normally see that the longest chain

is 5, and assume it is pentane; however, there is an iso unit in

the structure, so it could be considered isohexane now.

The good thing about this is that it doesn't matter what we

name it, for it will still have the same structure

AP Chemistry Study Guide (Part 3 of 3) Special Alkene, Benzene Benzene's chemical formula is C6H6 and is represented as a cyclohexane, but with every other bond alternating between double and single. It can be seen as one of 2 ways...

Either way is perfectly fine to represent benzene. The left picture shows the bonds, the right shows the dense electron concentration formed from the many bonds Benzene Nomenclature The nomenclature for benzene is quite simple. So I will just start with example.

\

Ortho-, Meta-, Para- When there is only 1 substituent attached, it is very basic. It's just the substituent as a prefix and benzene after it. SO the upper left example would be called: Ethylbenzene When there are 2 substituents attached, we would have to indicate the position of the substituents because there are 3 different possibilities. They could be at C1 and C2, C1 and C3, or C1 and C4 If at C1 and C2 it would be considered ortho (o-) If at C1 and C3 it would be considered meta (m-) If at C1 and C4 it would be considered para (p-) So if we look at the upper right example, there are 2 substituents, at C1 and C2 so it would be o-chloroethylbenzene Lower left example, 2 substituents, C1 and C3: m-cyclopropylethylbenzene Lower right example, 2 substituents, C1 and C4: p-diethylbenzene

AP Chemistry Study Guide (Part 3 of 3) We also have to take into consideration what to do if benzene is considered the substituent. It is called a phenyl if it is a substituent.

This molecule would be called, 2-phenyl pentane...It's as simple as that. Reactions Involving Benzene Benzene is capable of being hydrogenated but it isn't easy to do C6H6 + 3H2 C6H12 This is just like when we did this with an alkene, the double bonds will break and the Hydrogens will bond to the open carbons. We can also apply benzene to a new type of reaction, a substitution reaction. For these reactions, a Hydrogen from the ring will be replaced with part of whatever was added. This can be accomplished by adding halogens or a carbon group attached to a halogen C6H6 + Br2 C6H5Br + HBr

C6H6 + CH3CH2Br C6H5CH3CH2

AP Chemistry Study Guide (Part 3 of 3) Basic Functional Groups

Alkanes: -ane suffix Alkenes: -ene suffix Alkynes: -yne suffix Phenyls: Phenyl prefix Amines: Amine suffix Amides: Amide suffix Alcohols: -e to -ol suffix (i.e propane ---> propanol) Ethers: Ether ending Aldehydes: Aldehyde suffix OR -e to -al suffix (i.e Methane ---> Methanal) Ketones: Ketone ending OR -e to -one suffix (i.e Butane ---> Butanone) Carboxylic Acids: -ate/-ene to -ic/-oic acid ending. (i.e. Acetate ---> Acetic acid/Benzene ---> Benzoic acid) Esters: Combines alcohols with carboxylic acids. We name the carbon group to the right of the single bonded O, and then count the remaining carbons, including the one in the C=O, take the root of it, and change -e to -oate to it. Ester Nomenclature Level 1: Propyl Ethanoate

Naming The first step is to look at the carbon group to the right of the C-O bond, which comes out to be CH3CH2CH2

(propyl). Then we count how many remaining carbons there are including the one with the C=O bond. That comes out to 2. We then take the root of 2 which is ethane and change the -e to -oate

AP Chemistry Study Guide (Part 3 of 3) Level 2: Phenyl propanoate

Level 3: neo-pentyl methanoate

Organic Chemistry Overview

Type of Molecule Formula Hybridization Ending Alkane CNH2N+2 -------------------- -ane

Cycloalkane CN2N sp3 cyclo- -ane Alkene CNH2N sp2 -ene

Cycloalkene CNH2N-2 ------------------------ -ene Alkyne CNH2N-2 sp -yne

Alkanes - Root determined by the longest carbon chain. Carbons are numbered such that substituents will have the lowest number. -Exception: Iso-, Sec-, Tert-, Neo- The larger the molecule, the more LDF it has Saturated, building blocks of everything Alkenes - Root determined by the longest carbon chain that includes the double bond. Carbons are numbered such that the double bond will have the lowest number. Include a number prefix to indicate where the double bond is. Unsaturated, capable of being broken down more Alkynes - Root determined by the longest carbon chain that includes the triple bond. Carbons are numbered such that the triple bond will have the lowest number. Unsaturated, capable of being broken down more Include a number prefix to indicate where the triple bond is -Special alkyne: Acetylene Benzene- Substituents added, make substituent a prefix, if more than one substituent, include location by using o-, m-, or p- If it is substituent, it will be known as phenyl Formula C6H6 Cis vs. Trans: Cis-Hydrogens on the same side, Trans-Hydrogens on opposite sides of each other

Naming Step 1.) Look at carbon group to the right of the C-O bond, and it happens to be a benzene ring. And if you remember that when benzene is a substituent, it is called phenyl. Step 2.) Count remaining carbons, take the root, and change ending. 3 carbons, propane ---> propanoate

Naming Step 1.) Look at the carbon group to the right of the C-O bond, and it looks rather confusing; however, it is a vaguely familiar unit, called the neo unit. And because there are 5 carbons, we consider it a pentyl group. Putting it together we get neo-pentyl. Step 2,) Count the remaining carbons, take the root, and change the ending. 1 carbon, methane ---> methanoate.


Miscellaneous This section is to cover everything I didn't cover and is potentially important. 1.) Significant Figures You shouldn't be in AP Chem if you don't know your sig figs. When in doubt, use 3 sig figs 2.) Empirical Formula from Percent Composition Refer to Chapter 3 of Study Guide "Percent to mass, mass to mole; divide by small, times 'til whole" 3.) Determine Limiting Reactant Refer to Chapter 3 of Study Guide 4.) Strong Acids and Bases Refer to Chapter 14/15 of Study Guide 5.) Ions and Their Charge Column IA, IIA, and IIIA ions will have a charge of +1, +2, and +3, respectively Column VA, VIA, and VIIA ions will have a charge of -3, -2, and -1, respectively Transition metals will have multiple charges Refer to Chapter 2 of Study Guide for some common transition metal charges Additional transition metal ion charges: Ag+1, Zn+2, and Al+3 Polyatomic Ions:

Name Formula/Charge Name Formula/Charge Acetate CH3COO-1 Hypochlorite ClO-1

Ammonium NH4+1 Manganate MnO4

-2 Carbonate CO3

-2 Mercury (I) Hg2+2

Chlorate ClO3-1 Nitrate NO3

-1 Chlorite ClO2

-1 Nitrite NO2-1

Chromate CrO4-2 Oxalate C2O4

-2 Cyanide CN-1 Perchlorate ClO4

-1 Dichromate Cr2O7

-2 Permanganate MnO4-1

Dihydrogen Phosphate H2PO4-1 Peroxide O2

-2 Hydrogen Carbonate HCO3

-1 Phosphate PO4-3

Hydrogen Phosphate HPO4-2 Sulfate SO4

-2 Hydrogen Sulfate HSO4

-1 Sulfite SO3-2

Hydroxide OH-1 Thiocyanate SCN-1 6.) VSEPR Table/Hybridization

VSEPR Notation Shape Angle Hybridization Polarity B2, AB2, AB2E3 Linear 180° sp/sp2/sp3, sp, sp3d Nonpolar AB2E, AB2E2 Bent 120°, 109.5° sp2. sp3 Polar

AB4 Tetrahedral 109.5° sp3 Nonpolar AB3 Trigonal Planar 120° sp2 Nonpolar

AB3E Trigonal Pyramidal 109.5° sp3 Polar AB5 Trigonal Bipyramidal 90°-120°-180° sp3d Nonpolar

AB4E See-Saw 90°-120°-180° sp3d Polar AB3E2 T-Shaped 90°-180° sp3d Polar

AB6 Octahedral 90°-180° sp3d2 Nonpolar AB5E Square Pyramidal 90° sp3d2 Polar AB4E2 Square Planar 90° sp3d2 Nonpolar

Understanding the VSEPR First, here are some technical details as for when I made the graph. Everything is respective to each other, meaning that the order in one column will correspond to the order of another. For the first row, B2 will have sp/sp2/sp3 hybridization. A comma accounts for keeping everything respective of each other A dash signifies that that particular molecule will have all 3 of those angles


Understanding the VSEPR A: Central atom B: Non-central atom E: Lone pair of electrons on central atom If there is an ion, put the charge on the central atom. (+ charge, remove electrons - charge, add electrons)

Examples

SF6, ClF3, H3O+, I3-

SF6: Central atom of S, 6 non-central atoms of F. No lone pair of electrons on central atom AB6, octahedral, 90°-180°. sp3d2

ClF3: Central atom of Cl, 3 non-central atoms of F. Chlorine has 7 valence electrons (3 pairs, 1 unpaired). One of the F's will bond to the unpaired, and the other 2 will split up one of the pairs on the Cl and bond to one of the newly formed unpaired. So now that leaves 2 lone pairs of electrons on the central atom. AB3E2, T-Shaped, 90°-180°, sp3d H3O+: Central atom of O+, 3 non-central atoms of H O has 6 valence electrons (2 pairs, 2 unpaired). However, if we account for the +1 charge, we will take an electron away, making it 1 pair and 3 unpaired, in which the H's will bond to the 3 unpaired AB3E, Trigonal Pyramidal, 109.5°, sp3

I3-: Central atom of I-, 2 non-central atoms of I

I has 7 valence electrons (3 paired, 1 unpaired). However, if we account for the -1 charge, we will add an electron, making it have 4 pairs. In order for the other 2 I's to bond, they will split one of the pairs and bond to the newly formed unpaired electrons. AB2E3, Linear, 180°, sp3d

VSEPR In 5 Seconds The number of bonding domains will determine the hybridization. Bonding Domains: A site of a molecule where there is an unpaired set of electrons or a bond. 1 Bonding Domain: No hydridization 2 Bonding Domains: sp hybridization 3 Bonding Domains: sp2 hybridization 4 Bonding Domains: sp3 hybridization 5 Bonding Domains: sp3d hybridization 6 Bonding Domains: sp3d2 hybridization Orly? Yarly. (Proof) 2 Bonding Domain: CO2 (Two C-O double bonds, and no excess electrons). -VSEPR Notation: AB2 -Shape: Linear -Hybridization: sp Okay, that one was too simple, let's make it a bit harder. 4 Bonding Domains: NH3 (3 N-H single bonds. Set of electrons on the N) -VSEPR Notation: AB3E -Shape: Trigonal Pyramidal -Hybridization: sp3 6 Bonding Domains: XeF4 (4 Xe-F single bonds, and 2 sets of electrons) -VSEPR Notation: AB4E2 -Shape: Square Planar -Hybridization: sp3d2 Check on the previous page or even online if you must, but it will always work (most of the time).

AP Chemistry Study Guide (Part 3 of 3) 7.) Lewis Dot Structures to Determine Polarity

Symmetrical: Nonpolar

Unsymetrical: Polar

Confirmable through VSEPR table

8.) Calculate Percent Composition of Compound

Refer to Chapter 3 of Study Guide

9.) Gas Laws/Mole Fraction


n g

n

RT

10.)

11.) Hess' Law


12.) Δ , ΔS, ΔG of a Reaction roducts - Reactants)


H or G of pure element is 0

Alternative:

13.) Periodic Trends


14.) Formal Charge


15.) Sigma vs. Pi Bonds


16.) Bond Order


17.) Magnetism


18.) Intermolecular Forces


19.) Phase Diagrams


20.) Freezing Point Depression/Boiling Point Elevation


21.) Rate Laws and Corresponding Graphs


Q mcΔT Water hase hange

Q = Energy

m = mass of molecule

c = specific heat of molecule

ΔT hange in temperature in °

Q=mHvap

Q=mHfus

Hvap = 2260 J/g

Hfus = 334 J/g

AP Chemistry Study Guide (Part 3 of 3) 22.) Rate Constant, k, Units

Zero Order: Moles L-1sec-1

First Order: Sec-1

Second Order: L mole-1sec-1

23.) Energy Hill Diagrams

Exothermic: Endothermic:

24.) Determining Intermediate or Catalyst


25.) Keq Expression/Le Châtlier's Principle


26.) Q>K, Q<K, Q=K Relations


Refer to Chapter 14/15 of Study Guide for Ksp relationship

27.) ICE Charts


28.) Acid/Base Definitions

Refer to Chapter 14/15 of Study Guide

29.) Acid/Base Calculations


30.) Acid/Base Equilibrium/Titration


31.) pH of Salts

Strong base, weak acid: Slightly basic salt

Strong acid, weak base: Slightly acidic salt

Strong base, strong acid: Neutral salt

Salts involving transition metals will typically create colorful solutions

+1 +2 +3 +4 +6 +7 Cr Blue Green Chromate: Yellow

Dichromate: Orange

Mn Pale Pink Brown Dark Green Purple Fe Pale Green Yellow/Brown Co Pink Orange/Yellow Ni Green Cu Colorless Blue Zn Colorless

AP Chemistry Study Guide (Part 3 of 3) 32.) Determining the Stronger Acid


33.) Common Ion Effect


34.) Relationship Between ΔS, Δ , and ΔG


35.) Relationship Between ΔG and °cell


36.) Balancing Redox Reactions


LEO say GER

Loss of Electrons = Oxidation

Gain of Electrons = Reduction

37.) Calculating E°Cell and Ecell (Nernst Equation)


38.) Electrolysis


39.) Organic Names


40.) Drawing Isomers


41.) Radioactive articles: α, , and


42.) Balancing Nuclear Reactions


ap chemistry study guide (part 3 of 3) - amazon s3s3.amazonaws.com/cramster-resource/104049_part 3...

Documents