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MCAT > General Chemistry > Flashcards

General Chemistry Flashcards

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MCAT flashcards
1
Q

what is the equation for angular momentum of an electron? for energy of that electron?

A

L = nh/2pi

E = -Rh/n^2

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2
Q

pauli exclusion principle

A

no two e- in an atom can possess the same set of four quantum numbers

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3
Q

how to determine the maximum # of e- in a shell?

what is max # of e- in subshell?

A

2n^2, where n = principle quantum #

4L+2

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4
Q

explain the 4 quantum numbers

A
  1. n = principle quantum # (energy level) (also tells you # subshells)
  2. L = azimuthal (angular momentum) quantum # - refers to shape/#shells within given principle energy level
  3. mL = magnetic quantum # (specifies particular orbital within sub shell where e- is most likely to be found) (2L+1 possible values for mL)
  4. mS = spin quantum # (e- spin orientation) (+1/2 or -1/2)
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5
Q

how does n limit L? how does L limit mL?

A

L = 0 to n-1

mL = -L < mL < +L

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6
Q

explain spectroscopic notation

A

shorthand representation of principal azimuthal quantum #’s
L=0, called s; L=1, called p; L=2, called d; L=3, called f
ex) e- in shell n=4 is in 4d

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7
Q

explain electron configuration

A

first number denotes principal energy level (n), letter designates sub shell (L) , and superscript gives # e- in that shell
ex) 2p^4 means 4 e- in second (p) sub shell of second principal energy level

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8
Q

what is the aufbau principle?

A

electrons fill from lower to higher energy subs jells, and each sub shell will completely fill before electrons enter next one

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9
Q

what is hund’s rule?

A

within a given subshell, orbitals are filled such that there are a max number of half-filled orbitals w/ parallel spins

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10
Q

paramagnetic vs diamagnetic

A

paramagnetic is the presence of unpaired e- (and PARALLEL spins & ATTRACTION), while diamagnetic is paired e- (and REPELLED)

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11
Q

what are valence electrons? are they easy or hard to remove? explain groups

A

the e- in outermost energy shell, easiest to remove

  • Groups 1 & 2, only highest s subshell e- are valence
  • Groups 3-12, highest s&d subshell e- are valence
  • Groups 13-18, highest s&p subshell e- are valence
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12
Q

A elements

A

representative elements
IA-VIIIA
S or P subshells

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13
Q

B elements

A

nonrepresentative elements
transition/actinite/lanthinide series
S and D subshells

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14
Q

explain properties of each of the following: metals, nonmetals, metalloids

A
  1. metals - luster, malleable, low EN, high atomic radius, low e- affinity, EASILY GIVE UP ELECTRONS
  2. nonmetals - brittle, high IE, high EN, small atomic radius, DO NOT EASILY GIVE UP ELECTRONS
  3. metalloids - medium EN and IE, luster but brittle and poor conductor
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15
Q

what is Zeff? trend?

A

effective nuclear charge, it is the electrostatic attraction b/w valence shell e- and the nucleus

  • it is a measure of the net positive charge experienced by the outermost e-
  • increases going from left to right
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16
Q

what is the principal quantum # trend seen in the periodic table? what does it mean?

A

moving down a column, principal quantum # increases by one each time
- the valence e- are increasingly separated from nucleus by greater # filled principal energy levels, which reduces attraction b/w valence e- and nucleus, valence e- held less tightly

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17
Q

what is ionic radius trend?

A

increases as you go left to right because adding electrons increases size of atom

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18
Q

ionization energy; how does Zeff affect IE?

What is first vs second IE?

A

energy required to remove e- from gaseous species (endothermic)

  • larger Zeff or closer to valence e- means more tightly bound and thus a higher IE
  • 1st IE is energy to remove 1st e- and 2nd is for 2nd e-
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19
Q

electron affinity, what is the trend?

A

energy dissipated by gaseous species when it gains an e- (Exothermic)

  • essentially opposite of IE
  • increases going left to right, decreases top to bottom
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20
Q

define trends for AR, IE, EA, EN

A
  1. AR decreases L to R/increases T to B
  2. IE increases L to R/decreases T to B
  3. EA increases L to R/decreases T to B
  4. EN increases L to R/decreases T to B
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21
Q

octet rule exceptions

A
  1. Incomplete octet - these elements are stable w/ <8 e- (H, He, Li, Be, B)
  2. Expanded octet - any element in period 3 and greater, holds more than 8 e- (P,S,Cl, period 3 and greater)
  3. Odd # of e- - any molecule w/ an odd # of valence e- can’t distr. to give 8 e- to each (ex. NO has 11)
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22
Q

ionic bonding

A

one or more e- from an atom w/ low IE (usually metal) are transferred to an atom w/ high EA (usually nonmetal)
- ex. NaCl

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23
Q

covalent bonding; polar vs nonpolar

What is a coordinated event?

A

e- pair is shared b/w 2 atoms (usually nonmetal), w/ similar EN values
- if e- pair is shared equally it is nonpolar covalent, and unequally is polar covalent
A coordinated event is when both of the shared e- are contributed by only one of the 2 atoms

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24
Q

what are some characteristics of ionic compounds?

A

high MP, high BP, crystalline lattice in solid state (repeating + and - ions), dissolve readily in H2O, good electrical conductors in molten/aqueous states

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25
Q

explain bond strength and length of single, double, and triple bonds

what is bond order (for triple bond as an example)?

A

single - longest and weakest
double - medium and medium
triple - shortest and strongest

bond order is the # shared e- b/w 2 atoms (ex. triple bond has bond order of 3)

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26
Q

bond energy

A

energy required to break a bond by separating its components into their isolated gaseous atomic states

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27
Q

what are the diatomic elements that form non polar covalent bonds

A

H2, N2, O2, F2, Cl2, Br2, I2

28
Q

what is the equation for a dipole moment and define variables

A

p = qd

p is dipole moment, q is magnitude of charge, d is displacement vector separating 2 partial charges

29
Q

what is the formal charge equation?

A

FC = (V e-) - (NB e-) - 1/2(B e-)

30
Q

how to draw a lewis dos structure?

A
  1. draw out backbone of compound, least EN atom is central (H and usually halogens are terminal)
  2. count all Ve- and make sure sum is achieved
  3. draw single bonds
  4. complete octets
31
Q

VSEPR theory

A

uses lewis dot structures to predict molecular geometry

  1. draw lewis dot structure
  2. count total Be- and NBe- of CENTRAL ATOM
  3. arrange e- pairs around central atom so they are as far apart as possible
32
Q

electronic vs molecular geometry

coordination number

A

electronic describes spatial arrangement of all pairs of e- around central atom (including NB and B e-), while molecular describes spatial arrangement of only B e-
- # of atoms that surround and are bonded to central atom (helps determine geometry)

33
Q

bonding vs antibonding orbitals

sigma vs pi bonds

A

bonding is when signs of 2 atomic orbitals are the same, antibonding is when the signs are different

sigma is when orbitals overlap head to head, allowing for free rotation about their axes, while pi is when there are 2 parallel overlap e- cloud densities, and there is not free rotation

34
Q

rank intermolecular forces from weakest to strongest

A

london dispersion < dipole dipole < H bond < covalent

35
Q

what is a london dispersion (van der waals) force?

A

attractive/repulsive interactions of short-lived and rapidly shifting dipoles

36
Q

what is a dipole-dipole interaction?

A

a temporary positive attractive force from + end of dipole to - end

37
Q

what is the equation for gram equivalent weight? and explain equivalents in terms of hydrogen ions, for example

A

gram equivalent weight = molar mass/n

for H2SO4 (62g/mol), we’d need 31g in order to obtain 1 eq. of H+ ions.

38
Q

what is normality? what is the equation for converting from normality to molarity?

A

normality is a measure of concentration in equivalents/L

Molarity = normality/n (n is # protons)

39
Q

empirical vs molecular formulas

A

empirical gives the simplest whole number ratio of the elements in the compound, while molecular gives the exact # of atoms in the compound

40
Q

what is the equation for % composition of an element?

A

% composition = mass of element in formula/molar mass x 100%

41
Q

how to determine empirical and molecular formula?

A
  1. assume there are 100g -> each % x100g
  2. Divide each amount by molar mass
  3. Divide each resulting # by lowest number (3.3/3.3, 4.5/3.3)
  4. find lowest whole number ratio to fit
    MOLECULAR:
  5. divide total molar mass by empirical molar mass
  6. multiply empirical formula by that integer
42
Q

what is a combination reaction? example?

what is a decomposition reaction? example?

A

2 or more reactants forming 1 product
2H2 + O2 -> 2 H2O

1 reactant forming 2 or more products
2HgO -> 2Hg + O2

43
Q

single vs double displacement reactions w/ examples

A

SINGLE - occurs when atom/ion in compound is replaced by atom/ion of another element
Cu + AgNO3 -> Ag + CuNO3
DOUBLE - elements from 2 diff compounds swap places
CaCl2 + 2AgNO3 -> Ca(NO3)2 + 2AgCl

44
Q

combustion reaction & example?

neutralization reaction & example?

A
  • involves a fuel (usually hydrocarbon), an oxidant (usually O2). and they form CO2 and water
    CH4 + 2O2 -> CO2 + 2H2O
  • type of double-displacement where acid reacts w/ base to produce a salt (and usually H2O)
    HCl + NaOH -> NaCl + H2O
45
Q

talk about compounds ending in -ide, -ite, and -ate and starting with hypo- and per-

A
  • monoatomic anions end in -ide (H- = hydride, F- = fluoride)
  • when a compound forms 2 oxyanions, the one w/ less oxygens ends in -ite and more ends in -ate (NO2- = nitrite and NO3- = nitrate)
  • for extended series, hypo means less and per means more (hypochlorite, chlorite, chlorate, perchlorate)
46
Q

explain the collision theory

how do you incase reaction rate in arrhenius equation?

A

rate of rxn is prop. to # of collisions per sec. b/w reacting molecules

decrease Ea or increase temp.

47
Q

define the following

  • zero-order rxn.
  • first-order rxn.
  • second-order rxn.
  • mixed-order rxn.

dynamic vs. static equilibrium

A
  • zero-order rxn. - rate of formation of product is independent of changes in conc. of reactants (only temp. or catalyst can change rate)
  • first-order rxn. - rate prop. to only one reactant
  • second-order rxn. - rate prop. to conc. of either rxn
  • mixed-order rxn. - non-integer orders or varying orders

dynamic is when forward/reverse rxns are still occurring, static is when they’ve stopped

48
Q

relationship b/w Q and Keq

the larger Keq is _________

A
  • If Q < Keq then forward rxn has not reached eq. and more reactants than at eq; deltaG < 0
  • If Q = Keq then reaction is dynamic eq. and deltaG=0
  • If Q > Keq then forehead rxn. exceeded eq. and deltaG >0

the further to the right the rxn is

49
Q 
given reaction:
A (aq) + 2B (g) => C (g) + heat
will shift right if:
- 
- 
- 
- 
will shift left if:
- 
- 
- 
-
A 
Right:
- A or B added
- C removed
- P increases or V decreases
- T decreases
Left:
- C added
- A or B removed
- P decreases or V increases
- T increases
50
Q

isolated vs. closed vs. open systems

explain deltaU, G, Q for

  • isothermal
  • adiabatic
  • isovolumetric
A

isolated is neither energy nor matter can be exchanged w/ surr; closed is just energy but not matter can be exchanged; open is both can be exchanged

  • isothermal - deltaU=0, so Q=W
  • adiabatic - Q=0, so deltaU= -W
  • isovolumetric - deltaU=Q, no work done
51
Q

state functions mnemonic

standard conditions vs. STP

what is the relationship b/w alkane size and combustion?

A

when im under PRESSURE and feeling DENSE, all I want is TV and HUGS

standard conditions is 25C (298K), 1atm pressure, 1M; STP is 0C (273K), 1atm

larger alkane = larger combustion

52
Q

LOOK UP AND KNOW EVERY SPACE AND LINE OF A PHASE DIAGRAM

A

OKAY

53
Q

define endo and exothermic (Q and H)

when is bond enthalpy positive? negative?

what is the change in entropy equation?

A

endothermic is deltaQ>0 and deltaH>0, so the system absorbs heat; exothermic is deltaQ<0 and deltaH<0, so the system releases heat

positive when breaking bonds, negative when forming bonds

S=Qrev/T

54
Q

converting b/w atm and mmHg? what volume does 1mol gas occupy at STP?

what is boyle’s law (V vs. P) and charles’ law (V vs. T) and Gay-Lussac’s law (P vs. T) and Henry’s law ([A] vs. P)?

A

1atm = 760mmHg

22.4L

P1V1=P2V2; V1/T1=V2/T2; P1/T1=P2/T2; [A1]/P1=[A2]/P2

55
Q

when new interactions are stronger than initial ones, solvation is _____ and then new ones are weaker it is_________

what are the first 2 solubility rules?

A

exothermic; endothermic

  1. all salts containing NH4+ and alkali metal (group1) CATIONS are water-soluble
  2. all salts containing NO3- and CH3COO- ANIONS are water-soluble
56
Q

molarity vs. molarity (units)

what is normality?

what is the dilution equation?

A

molarity is mol/L and molality is mol/kg

normality (N) is # eq. of interest per L of soln

MiVi=MfVf

57
Q

what is the common ion effect?

how does adding solvent affect vapor pressure? (Raoult’s law)

what is boiling point elevation formula? freezing point depression formula?

A

solubility of a salt is reduced when dissolved in soln already containing one of the constituent ions

adding solute decreases vapor pressure of solvent

deltaTb = iKbm
deltaTf = iKfm
58
Q

bronsted-lowry acid vs base?

lewis acid/base?

amphoteric? amphiprotic?

A

BL acid donates H+, BL base accepts H+

Lewis acid is e- acceptor, lewis base is e- donor

amphoteric can be acid or base; amphoprotic can gain or lose H+

59
Q

how to solve for -log(n x 10^-m) ?

equation for finding unknown concentration of titrand? (N and V)

A

m - 0.n

NaVa = NbVb

60
Q

oxidation # rules

A
  1. free elements have Oxid. # of 0
  2. Oxid. # of monoatomic ion is equal to the charge (Na+ = +1, Cl- = -1)
  3. Group I oxidation # is +1
  4. Group II oxidation # is +2
  5. Group VII is -1 EXCEPT when combined w/ higher EN atom
  6. Hydrogen is usually +1, sometimes -1 w/ less EN atoms
  7. Oxygen is usually -2
  8. sum of oxidation # in neutral compound is 0
61
Q

how to balance half rxn in acidic soln? basic soln?

what is a spectator ion?

combination vs decomposition reactions

A

Acidic - use H2O to balance O and H+ to balance H
Basic - use OH- to balance O and H2O to balance H

ion that is unchanged in charge across the reaction

combination is when 2+ species come together to form a product, decomposition is when 1 product breaks into 2+ species

62
Q

what is a combustion rxn?

what is a double displacement rxn?

what is a disproportionation rxn?

A

a fuel (usually hydrocarbon) is mixed w/ oxidant (usually Oxygen) forming CO2 and H2O

when counter ions switch places

element undergoes both oxid. and red. in producing its products

63
Q

electrodes in electrochemical cell mnemonic

what is electromotive force (emf)? +emf vs -emf

which direction does current flow in electrochemical cell? which direction do e- flow?

A

AN OX and a RED CAT
- anode does oxidation and cathode is reduction

emf is voltage or electrical potential diff. of the cell
- + emf cell is able to release energy (deltaG<0) and -emf cell must absorb energy (deltaG>0)

cathode to anode
A->C

64
Q

how to construct a cell diagram? (ex)

galvanic vs. electrolytic cell

electrodeposition eq. and mnemonic

A

Zn | Zn2+ (1M) || Cu2+ (1M) | Cu
anode | anode soln (conc.) || cathode soln. (conc.) | cathode

galvanic is spontaneous, electrolytic is non spontaneous and requires electrolysis (chem. comp. decomp.)

mol M = I(t)/nF
calculating mol. M, It is Not Fun

65
Q

what is unique about a concentration cell?

what is a rechargeable cell?

what is energy density (high vs. low)?

A

it is a type of galvanic cell (spontaneous), but the electrodes are chemically identical, therefore current is generated as a function of concentration gradient established b/w the two solutions

cell that can act as galvanic or electrolytic

measure of battery’s ability to produce power as a function of weight (low energy density requires heavier amount of battery material)

66
Q

in cells, when is anode positive/negative and cathode positive/negative?

what is reduction potential (talk about high vs. low)
- talk about electrodes in each cell w/ their reduction potential

A
  • galvanic cell, anode negative and cathode positive
  • electrolytic cell, anode positive and cathode negative

tendency for species to gain e- (be reduced); more positive means more likely to be reduced
- galvanic cells have more positive RP in cathode, electrolytic cells is anode

67
Q

how are deltaG and emf related?

what is nernst eq. for cells?

A

deltaG = -nF(Ecell)
n is mol of e- transferred, E cell is standard emf

Ecell = E(0)cell - RT/nF(lnQ)

MCAT (8 decks)

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