Subatomic particles found in the nucleus with a (+1) charge. Mass equals one atomic mass unit and identifies the identity for each element.

Number of protons = atomic number "Z"

Atomic number is the numnber of protons or "Z" of an element

Mass number is the number of protons and neutrons.

Differing the number of neutrons results in different isotopes of the same element, but differing the numbers of protons results in a new identity of the element.

The weight in grams for one mole of atoms for a specific element.

(one gram = one amu)

Energy emitted as electromagentic radiation resides in discrete bundles that is the magnitude of plancks constant (6.626x10^-34 J*s) and the frequecy of the radiation.

This equation is only good for one single photon...must look closely to make sure that the question is asking for energy for a single photon not more like a mole of photons

L = nh/2∏

Angular momentum of electron

E = - (2.18x10^-18)/n²

Energy of electron

The energy emitted as a photon resulting from the absorption of energy is related to (6.625x10^-34*3x10⁸)/Wavelength.

As the wavelength of the radiation decreases then the amount of energy emitted increases. E=1/λ

Emission Spectra are the spectra lines resulting from excited atom emitting emits specific radiation dependent on the energy gap between the ground state and the excited state

Absorption spectra are the spectra line where there are several dark lines resulting in the energy that is absorbed by the element.

( in general we see the color of light not absorped)

The principle that states how the position and momentum of an electron can not be known at any given amount of time.

In order to know momentume, the velocity must be known therefore these two variables can be known simulatenously

The difference in energy between two shell decreases as the distance from the nucleus increases.

Therefore eneryg difference between n = 1 and 2 is greater than 2 and 3 --> so on  

Paramagnetic - materials with unpaired electrons that are attracted to magnetic fields by orienting unpaired spins with the magnetic field

Dimagentic - materials with all paired electrons that are repelled by magnetic fields

Set up a two algebra equations where the x + y = 1 corresponding to the propportion of one isoptope and another is equal to 100%

The second equation is the amu of x plus amu of y = total amu. Solve for one variable in the first equation in input value into second. Then solve.

Period is the row of elements. There are 7 periods and every element to the right has one more proton and electron.

Groups are the columns of elements that have similar properties. Elements within groups have similar electron configuration and same number of valence electrons

one-half the distance between the centers of two atoms of an element in brief contact with one another.

Atomic radius can not be measured from a single atom because the boundary of an atom with electrons constantly moving is impossible to determine

Effective nuclear charge increases from left to right across a period. Increasing electrostatic attraction across a period causes the valence shell of an electron to feel a greater pull reducing the radius. Down a group the atomic radius increases due to the increased number of filled valence shell around the nucleus

Increase - left to right, top to bottom

Electron affinity increases from left to right across a period because of the strong effective nuclear charge. The stronger electrostatic attraction between the nucleus and the valence shell causes greater energy release when atom gains electrons. Electron affinity decreases from top to bottom because the valence shell is farther away from nucleus.

Increases - left to right, bottom to top 

Ionic bond is the transfer of electrons from atom w/ low ionization energy to atom with high electron affinity (metal and nonmetal) , which resutls in a electrostatic force of attraction between the opposite charges

Covalent bond is the unequal sharing of electron pair between two atoms of similar electronegativity.

Nonpolar bonds - electron pair are equally shared between two atoms

Polar bonds - electron pair are unequally shared between two atoms 

Polar coordinate covalent - shared electrons are contributed by one of the two atoms (lewis acid-base)

The formal charge of a compound is the difference between the number of valence electrons an isolated has compared to the number of valence electrons associated with the atom based on its Lewis structure.

1. Count total number of valence electrons
2. Make the least electronegative atom the central atom and add the other elements around it
3. Complete octets of surrounding elements and put additional electrons on central atom

1. Focus on formal charges and lewis structures with no or small formal charges are preferred.
2. Lewis structures with small seperation of formal charge versus large separation
3. Lewis structures where negative formal charge are associated with the more electronegative atom

(120^o)

3 electron densities around central atom

Usually associated with atoms with sp² hybridized atoms

109.5^o

4 electron densities surround the central atom

Usually associated with sp³ hybridized compounds

Electron geometry is the arrangement of electron pairs and electron denisites around the central atom.

Molecular geometry is the electron densities that explains the angles and angle deviation due to lone pairs, yet do no include the lone pairs in the geometry

It depends on the overall dipole moment. If the vector sum of the polar bonds add up to zero, then the compound is nonpolar because there is no dipole moment. However, a net dipole moment (after the vector addition of the seperate polar bonds not resulting in zero) results in a polar compound.

depending on the molecular geometry of the compound will dictate whether or not the bond dipoles cancel or not

Standard conditions refer to 25^oC (or 298K) and 1atm and are used for entropy, gibbs free energy, enthalpy problems

STP or standard temperature and pressure refer to problems involving the ideal gas law such as 0^oC (273K) and 1 atm

Van der Waals forces

London Dispersion Forces

Dipole-Dipole Interactions

Hydrogen Bonds

Ionic Bonds (strongest)

London Dispersion and dipole-dipole forces.

Dispersion forces are the weakest of all IMFs because they are only due to induced dipoles between nonpolar molecules. These dipoles are transient and constantly shifting and only significant between molecules close to another. Dipole-dipole interactions are due to polar molecules that have permant dipoles and orient themselves in manner in which positive and negative ends are close together. They have stronger electrostatic attraction.

Hydrogen bonds are the strong dipole-dipole interactions between electronegative atoms of (N, O, F). There is no sharing or transfer of electrons, but the hydrogen has a small amount of electron denisty which results in it carrying a postive partial charge which interacts with the partial negative charge of (N, O, F)

Substances with hydrogen bonds have very high boiling points

Dipole moments are based on the molecular geometry of compounds. The moment that produces the greatest net dipole without any canceling dipoles will have the largest moment. For example, a molecular geometry with linear shape will have a stronger moment than bent.

Remember to draw out the vector and vector add them to see which one is larger = which one is more polar

the number of ions, electron, protons, hydroxides, or hydrogens that a compound can produce

"mole of charge"

Normality is the number of equivalents per liter --> 1N is 1 mole/liter and 2N is 2 mole/liter

multiplying the number of equivalents by the molarity of the acid or base is the normality of that compound.

Basically, the percent composition is the mass of a particular element in the formula divided by the molecular weight x 100%

First, if percentages are given then assume 100g of the sample and divide percentage by the individual molar masses. Divide the moles by the smallest value obtained and multiply by integer to get whole number for the empirical formula. Divide the molecular mass of sample by the mass of the emipircal formula to get integer at which the empirical formula should be multiplied by.

Or

Multiple the percentage by the total molecular mass and divide by the atom molar mass to get the total number of atoms. Divide by integer to get the mole ratio for each element (empirical formula)

How to determine the limiting reagent?

(ex - C₃H₈ + 5O₂ --> 3CO₂ +4H₂O w, reacting mass of 22g of  propane and 48g of oxygen)

The limiting reagent must be determine based on the molar mass ratio of the given mass of the reactant over the molar mass of the reactants based on the stoichometric values

Ex --> moles/mass for propane = 1 mole w/ molecular mass of 44/22 = 2 mass ratio

oxygen = 5 moles at 32g each = 160/48 roughl 3 mass ratio --> oxygen is getting used up much faster

P_T = P_a + P_b + P_c ....

Gases behave independently one another in a vessel so if you see any question asking how the presence or any action on one gases affects another then you know it doesnt (as long as there are no chemical interaction between the gases)

1. fluids
2. move rapidly
3. far apart from each other
4. weak intermolecular forces (dispersion forces)
5. expand to fill any volume
6. compressible
7. Take on shape of container

P_A = P_TX_A

_and

X_a = n_a/n_T

1. have no intermolecular interactions
2. occupy no volume

1. Gases particle have negligible volume
2. gas atoms/molecules exhibit no intermolecular attraction/repulsion
3. continuous randomly moving particle colliding with one another
4. collision are completely elastic maintaining momentum and kinetic energy after collision
5. Average kinetic energy is proportional to absolute temperature

K.E. = 3/2kT

average speed of gas particles is related to temperature, the speed of individual gas particles is impossible to calculate

Explain the root mean square speed of gas particles equation 

√3RT/M

[image]

What does this plot depict?

The movement of gas molecules in a mixture. The heavier gases diffuse slower than the lighter gases due to differing average speeds. In isothermal and isobaric conditions, the rates are inversly propotional to the square root of the masses.

r₁/r₂=√m₂/m₁

The flow of gas particles under pressure from one compartment to another through a small opening. The rates are proportional to the average speeds and inversely proportional to the molar masses

r₁/r₂=√m₂/m₁

If pressure and temperature are constant based on ideal gas law, no matter what the identity of the gas they will occupy volume proportional to the number of moles. If there is an equal amount of moles, there will be an equal amount of volume. At STP, this relation for 1 moles signifies 22.4L --> 2 moles 44.8L and so on.

n₁/V₁=n₂/V₂

R = 8.21x10^-2 (L x atm)/(mol x K)

or

R = 8.314 J/(K x mol)

P = d x RT/M

d = m(mass in grams)/V

M = molar mass

P₁V₁/T₁ = P₂V₂/T₂

This graph represent the relationship between pressure and volume under isothermal or contant temperature conditions. This graph represents equation

P₁V₁ = P₂V₂ and shows how when increasing pressure of gasses volume decreases and vice versa

Be familiar with this graph

[image]

[image]

Explain this equation and what are the two main variables present!

a - represents the correction based on attractive forces (it is smaller for small,less polarizable gas atoms and larger for larger/polarizable gases)

b - represents the volume of molecules (large for large molecules and vice versa)

This equation is related to the way to real gases behave based on ideal gas law

1. determine the amount of limiting reagent and that number of moles is the number of moles of the other reactant

2. substract the number of moles of the limiting reactant from the excess reactant

3. the remaining moles of the excess reactant is converted to grams to determine the amount

What is the reaction rate with respect to each component of a general reaction?

[image]

Equillibrium relates to the end of reaction when the system has reached equillibrium

Kinetics is measured at the beggining of the reaction focusing to lessen the effect of the reverse reaction

1. rate is independent of the change in concentration

2. rate is constant and equal to rate constant

3. units M*s^-1

^{4. dependent on temperature and addition of catalyst}

1. rate is proportional to one reactant

2. units = s^-1

3. molecule undergoes a chemical reaction all by itself

What does a first order reaction graph look like with respect to rate and concentration?

1. rate proportional to either product of two of the same or different reactants

2. units M^-1s^-1

What does the graph for a second order reaction look like with respect to rate and concentration?

What does the graph for a second order reaction look like with respect to concentration and time?

1. reactions with fractions or nonintegers orders

2.

1. collide in correct orientation and sufficient energy to break the existing bond

2. rate is proportional to the number of collisions per second

1. complex where old bonds are breaking and new bonds are forming

2. exist as continuum that dont have distinct identities

1. negative enthalpy sign, heat is released

2. postive enthalpy sign, heat is absorbed

1. concentrations -- greater the #, greater # of collisions

2. rate increases as temperature increases (increasing the average kinetic energy of the molecules)

3. medium - aqueous environment vs nonaqueous environment (prefer polar solvent due to dipoles polarize the bonds, increasing rate) 

4. catalysts

1.  Substance that increase reaction rate by decreasing the activation energy without being used up

- change the forward and the reverse rate by the same factor

***no effect on equilibrium

2. increase frequency of collisions between reactants, change the orientation of the reactants, make a higher percentage of collisions effective, donate electron density, reduce intramolecular bonding

3. homogenous - catalyst/reactant same phase while heterogeneous - catalyst in distinct phase

(1) arrhenius--> acids = produce H+, base = produce OH-

(2) bronsted-lowry --> acid = donate hydrogen ions, base = accept hydrogen ions

(3) lewis --> acid - accepts electron pair, base - donate electron pair

(1) arrhenius --> requires an aqueous liquid, bronsted lowry --> does not \

(2) bronsted-lowry always comes in pairs (conjugate acid/base)

(3) F- --> bronsted base but can not be an arrhenius base because it can not produce hydroxide ions

(1) -ite anions become -ous acid

(2) -ate anions become -ic acid

(1) nitrous acid = HNO₂

(2) nitric acid = HNO3

(1) nitrate = NO_3^-

(2) nitrite = NO₂^-

(1) water is an amphoteric molecules so it can act as a water or base --> this property allows water the ability to react with itself to produce equal amounts of hydronium and hydroxide

(2) this reaction is also reversible

(3) H₂O + H₂O <--> H₃O⁺ + OH-

(1) the equilibrium expression that for pure water at 25^oC or 298K --> the equillibrium constant = 10^-14

(2) concentration of hydrogen ions and hydroxide ions are always equal for pure neutral water - concentration of 10^-7

(1) hydronium and hydroxide are in equal portions in neutral pure water --> any species that donates either hydronium or hydroxide ions disturbs this equilibruium

(2) the system reacts when there is an increase in either product (hydronium or hydroxide) causing a shift the equillibrium back towards to reactants and hence decreasing the other product 

(3) no matter what the reaction will shift back to equillibrium concentrations of both ions at 10^-14

(1) it doesnt change because it is an equillbrium constant --> equillibrium constant are only affected by changes in temperature 

(changes in pressure, concetration, or volume will HAVE NO AFFECT ON ANY EQUILIBRIUM CONSTANT)

(2) concentrations of hydrogens versus hydroxide results in an equal product of 10^-14

(3) increase the temperature above 298K then K_w increases

What is the p-scale and describe its context in regards to acid/base chemistry?

(1) p scale is the negative logarithm or the negative power raised from base 10 that equals the log 

(2) pH = -log[H⁺], pOH = -log[OH^-]

(3) pH + pOH = 14

(4) acidic = pH less than 7 or pOH greater than 7

(5) basic = pH greater than 7 or pOH less than &

(1)simple change formula to -log(5.6) + (-log10^-7)

(2) log of any power raised to 10 = exponent --> 7

(3) log of any n value between 0 and 10 is between 0 and 1 --> roughly .5

(4) 7-.5 = 6.5 roughly

(1) they completely dissociate into their ions in aqueous states --> there will be no acid/base reamining in the solution

(2) it is important they have higher concentration than 10-7 because then the concentration of bases and acids from amphoteric water can be neglected

(3) if less than 10^-7 such as 10^-8 or ^-9 then the contribution from water ions must be added

(1) the pH can not just be taken based on the exponent becuase for example if 1x10-8 or 10-9 of HCL acid is the species in question it cant really have pH of 8 or 9 cause it is not acidic

(2) MAIN THING TO REMEMBER is that there are for these example 10x or 100x respetively less acid or base compounds in the solution compared to the equillibrium

(3) there are common ions in the water for example H+ --> result in system to shift away from the H+ or OH- ions to the hydrogen reactants

hydrochloric acid- HCl

hydrobromic acid - HBr

hydroiodic acid - HI

sulfuric acid  - H₂SO₄

nitric acid - HNO₃

perchloric acid - HClO₄

sodium hydroxide

Potassium hydroxide

soluble hydroxides from the metals of the first/second row

(1) strong acid means it completely dissociates in aqueous liquid are creates a concentrated solution

(2) weak acid means it partially dissociates in aqueous liquids and create just dilute liquids

(1) decribe the equillibrium values for how water reacts with an acid or base

(2) the smaller or more negative exponent the value = weaker the acid or base

(1) it equals K_w 10^-14

(2) the net reaction of an acid-base equation in water results in the typical reaction of acid-base reaction in water

(3) if you know the dissociation constant for one reaction then you understand the reaction for the other

(1) equation using a dissociaton constant to calculate the concentration of H+ or OH-

(2) write out the acid dissociation constant

(3) whatever the initial concentration is of the reactant will be the denominatior if its a weak acid

*** if strong acid than whatever the intial concentration of the reactant will now be the value for the product

(1) strong acid + strong base

(2)Strong acid + weak base

(3)weak acid + strong base

(4) weak acid + weak base

What are the properties of a neutralization reaction between a strong base and acid?

EX)

(1) produce equal amount of salt and water

(2) pH will be neutral - cause the acid and base neutralize each other

(3) HCl + NaOH --> NaCl + H₂O

What are the properties of a neutralization reaction between a strong acid and weak base?

Explain what is the result of HCl +NH₃ <--> NH₄Cl

(1) always produce salts but water isnt usually formed because weak bases are MAINLY AMINES

(2) the resulting NH₄Cl can dissociate in aqueous solution resulting in the conjugate acid that is stronger than the initial NH₃ --> conjugate acid will then react with water to produce a hydronium ion which drive the autoionzation reaction back toward the reactant of water

(3) reduction in hydroxide ion and result in a pH lower than 7

What are the properties of a neutralization reaction between a weak acid and strong base?

Explain what is the result of HClO +NaOH<--> NaClO +H2O

(1) the salt formed will dissociate in water and react with water to form a very strong conjugate base that abstracts hydrogen from water producing more hydroxide ions

(2) this results the pH to increase to be basic

(1) it is more of a combination reaction resulting in a salt

(2) the pH is dependent on the Ka or Kb that is larger

What is a titration?

What are the different types on the MCAT to be prepared for?

Explain

(1) a procedure used to determine the molarity of a known reactant in a solution

(2) three main types --> redox, acid-base, metal ion titrations

(3) basically a known volume of solution with unknown concentration is reacted with a known volume of a solution of known concentration

(1) equivalence point is when the number of acid equivalents = number of base equivalents

(2) multiple equivalence points for polyprotic acids/bases

(3) determined via a pH meter or an indicator (indicators will change in color)

(1) end point is when the indicator changes color --> does not signify the equivalence point

(2) slowly adding the titrant then the equivalence point and endpoint can be the same value

(3) with the known concentrations/normalities and now known volume --> use equation N_aV_a=N_bV_b

What kind of titration is this?

[image]

What kind of titration is?

[image]

What kind of titration is this?

[image]

titration of a weak acid with a strong base

(1) equivalence point is in basic region --> a stronger conjugate base is produced with the reaction of a weak acid and strong base --> creating more hydroxide ions

(1) buffer solution are mixture of weak acid and its conjugate base (strong) or weak bases and its conjugate acid (stron)

(2) resists changes in pH by for example when a strong base hydroxide is added to a buffer --> the hydroxide react with H+ ions to produce water --> equilibrium shifts the the acetic acid acid which is the weaker acid

(3) weak acid neutralizes the strong base as the hydrogen

What is the purpose of the henderson-Hasselbalch equation?

If the concentrations of both buffer components are changed but there is no change in overall ratio such as doubling both, what is the effect on the buffer system?

(1) estimates the pH or pOH of a soluting in a buffer region where the concentrations of the conjugate acid/base over the weak base/acid

(2) if the ratio is consistent than the logarithm wont change resulting in the same pH --> but the buffering capacity or the ability to maintain the buffer will increase or decrease dependent on the change in concentrations

(1) the rate of the forward reaction = the rate of the reverse reaction

(2) the concentrations of the product and reactant are changing but there is no net change in the concentrations of the product or reactants

(3) a reaction reaches equilibrium is when the system is at the greatest entropy and the lowest Gibbs free energy

the purpose of the law of mass action is when a system is at equilibrium for a specific temperature than the ratio of the products over reactants will equal a constant after it is known the reaction is at equilibrium --> this equation is based on the rate of the forward and reverse reaction being equal

[image]

(1) the law of mass action determines the point of equilibrium

(2) the reaction quotient give an idea of how far along in a reaction is approaching equilibrium --> this equation is based on any point in the reaction not at equilibrium to determine where the reaction is

 Qc is less than K --> not at equilibrium(proceeds forward)

Qc = K --> reaction is at dynamic equilibrium

Qc is greater than K --> reaction has exceeded equilibrium  (proceeds in reverse )

(1) the system will react in the direction away from the species added or toward the direction from where the species was removed

(2) reactions that involve gases -- decrease volume/increase pressure then system will favor side with less gas molecule, increase volume/decrease pressure then system will favor side with more gas molecules

(3) heat is a product --> shift to the products when temperature is decreased and shift to reactants when temperature is increase, vice versa for heat as a reactant 

(1) isolated system --> system where neither energy nor matter can be exchanged with the surroundings

(2) closed --> system where only energy not mass can be exchanged with the surroundings

(3) open --> system can exchange both energy and mass to the surroundings

(1)  temperature, pressure, volume, density, internal energy, enthalpy, entropy, gibbs free energy

(2) merely describe the state of the system and compare them to another state --> heat and mechanical work are the methods of which these state function are reached

What is the specific heat?

(1) constant pressure "coffee cup calorimeter" --> an insulated container that is covered with a lid and filled with a solution in which a reaction occurs

(2) the heat transferred to or out of the system is the result of the mass of the substance * specific heat * the change in temperature of the system

(1) it is a decomposition vessel is merely a combustion reaction where a sample is placed in a vessel filled with gas --> this vessel is placed in a container with a known mass of water --> the content in the vessel is heated and the sample (hydrocarbon) usually combust with the presence of oxygen release heat into the system

(2) the PV work is done since there is no change in the volume --> the system is isolated so no heat is transferred out of the system

(3) the mcΔT of the sample + the mcΔT of oxygen = the -mcΔT of the water surrounding the system 

(4) it is an adiabatic proces --> no heat is exchanged with the system

(1) the change in heat of system in isobaric conditions is the measurement of enthalpy

(2) the change in enthaply = to the transfer of energy due to temperature differencess in to or out of a system in isobaric conditions

(3) calculated as the change in the enthalpy of the reaction = enthalpy of the products - reactants

(4) + = endothermic, - = exothermic

(5) standard heat of formation, standard heat of reaction, Hess law, bond dissociation energy, heat of combustion

(1) standard heat of formation are for standard state of 1 mole of a compound formed directly from its elements in their standard states

(2) the enthalpy of formation

(2) standard states are based on 298K, 1 atm, for any elements is 0

(1) the hypothetical enthalpy change that would occur if the reaction were carried out under standard conditions

(2) calculated by taking the sum of the standard heat of the formation for the products - the sum of the reactants

(1) make sure to switch signs when reversing the equation

(2) multiply by the correct coefficients when doing calculations

(1) this is the equation for the transfer of energy based on temperature differences from the results of breaking the bonds of reactants molecules and forming the bonds of product molecules

(2) [image]

(3) remember that to break bonds requires energy (endothermic) to form bonds releases it (exothermic)

(1) the transfer of energy (heat) from different bodies that is the result of the combustion of alkanes

(2) oxygen is not the only diatomic oxidant (species getting reduced or getting electrons) --> other molecules such as fluorine can be used

(1) it is a combustion reaction because large amounts of energy is produced

(2) they are both initially at oxidation staes of 0

(3) Hydrogen is the reducing agent as it is oxidized and Chlorine is the oxidizing agent because it is reduced (gains electrons)

(1) entropy is just the natural process of reactions and sytstems to spread out their energy --> energy wants to always spread out spontaneously

(2) it is measured as --> the change in the dispersal of energy is the transfer of energy due to temperature differences in a reversible reaction over the temperature

(3) entropy increases when energy is distributed into a system and decreaes when it is dispersd out of system

(4) in order for energy to be concentrated work must be done to do so

(4) as state function --> entropy change is not dependent on the manner of which the state is accomplished in regards to transfer of energy in the form of heat or work --> its change is purely dependent on the final and initial state

(1) this is a state function that determines the amount of energy released by a process in order to determine whether or not it will occur spontaneously or not at a constant pressure and temperature ( the energy produced is based on the parameters of both enthalpy and entropy)

(2) [image]

(3) negative G = spontaneous reaction, direction proceeds to completion in order to reach equilibrium 

positive G = nonspontaneous, direction will proceed to completion in the opposite direction in order to reach equilibrium

= 0 at equilibrium

(1) ΔH = +, ΔS = - -----> not spontaneous at all temp

(2) ΔH = - . ΔS = + ---> spontaneous at all temps

(3) ΔH = +, ΔS = + ---> spontaneous at high temp

(4) ΔH = -, ΔS = - -----> spontaneous at low temp

(1) it is not affected only the rate of the reaction is affected by Ea

(2) therefore catalyst will not affect the spontaneity of a reaction

(1) the first equation helps you to understand the amount of free energy change that occurs when a reaction goes from standard state concentration to equilibrium concentrations of reactants and products, and the spontaneity of the reaction

(2) greater K = more negative gibbs (more spontaneous)

(3) when a reaction is not at standard states so once it starts to occur --> the reaction quotient must be used to determine the change in gibbs free energy with combination of the first equation

(4) the last equation is a form of the second that can be used to determine the spontaneity of a reaction at a certain point

Q/K (less than 1) = negative Gibbs spontaneous

Q/K (greater than 1) = positive Gibbs nonspontanous --> spontaneous in the reverse direction

G/K = 0 = equilibrium

(1) [image]