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MCAT > general chemistry > Flashcards

general chemistry Flashcards

1
Q

what is plancks relation? plancks constant?

A

E = hf
E (energy of a quantum)
h = 6.626x10^-34 J.s
f = frequency

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2
Q

what is bohrs equation for angular momentum?

A

L = (nh)/2pi

n = quantum number
h= plancks constant = 6.629 x 10^-34 J.s
L = angular momentum
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3
Q

what is hunds rule?

A

that within each subshell, orbitals are filled such that there are a maximum number of half filled orbitals with parallel spins

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4
Q

what does paramagnetic mean?

are they electrons paired or unpaired in these atoms?

A

the electrons are unpaired

  • the spin of the electrons will be parallel to the magnetic field, therefore, will be attracted to magnets
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5
Q

what does diamagnetic mean?

are electrons paired or unpaired?

A

electrons are paired

  • the spin will repel the magnetic field!
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6
Q

what is heisenburgs uncertainty principle?

A

cannot measure momentum and position of electron cloud with precision because to measure momentum, you must move positions - and to measure position you cannot have momentum

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7
Q

what is the rutherford model?

A

dense, positively charge nucleus

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8
Q

bohr model?

A

attempt to describe behavior of single electron cloud hydrogen

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9
Q

periodic properties of the elements:

Zeff ?

A

effective nuclear charge

- for the same period, increases left to right

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10
Q

periodic properties of the elements:

atomic radii?

A

increases right to left, and top to bottom

-largest being cesium, smallest being helium

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11
Q

periodic properties of the elements:

ionic radii?

A

nonmetals - increases right to left and top to bottom toward metalloid line

metals - increases right to left and top to bottom away from metalloid line

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12
Q 
periodic properties of the elements:
ionization energy (IE)
A

energy required to remove an electron from a gaseous species

  • increases with increased Zeff
  • increases left to right and bottom to top
  • subsequent removal of electrons will require increasing amounts of energy (because increasingly cationic molecule)
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13
Q

periodic properties of the elements:

electron affinity

A
  • energy dissipated by gaseous species when it gains electron
  • increases left to right, bottom to top
  • noble gases = 0 (because stable octet)
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14
Q

periodic properties of the elements:

electronegativity

A

increases left to right, bottom to top

  • exceptions are the first three noble gases, which are inert
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15
Q

what group is the chalcogens?

A

group 16

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16
Q

which atoms follow octet rule for covalent bonding?

A

C, N, O, F, Mg, Na

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17
Q

ionic vs covalent:

melting point?
solid state structure?
good conductor or poor?

A

ionic - high melting point, crystalline lattice, good conductor

covalent - low melting point, poor conductor

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18
Q

dipole moment equation

A

p = qd

q = magnitude of charge
d = displacement vector separating two partial charges
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19
Q

formal charge of lewis structure equation?

A

formal charge = valence e/s - dots and sticks

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20
Q

for lewis structures, what are some exceptions that do not need full octets?

A

H (2), He (2), Li (2), Be (4), B (6)

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21
Q

intermolecular forces -weakest to strongest?

A

london dispersion < dipole-dipole < H bond < covalent < ionic

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22
Q

what three electronegative atoms is H attached to to form H bonds?

A

FON

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23
Q

when ammonium is formed from ammonia, what kind of bond is being formed?

A

coordinate covalent

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24
Q

which has a higher boiling point, acetone or isopropyl alcohol?

A

both have dipole-dipole, but isopropyl because OH can form H bonds with other molecules !

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25
Q

what does formula unit/weight indicate about the bond between two atoms?

A

that it is ionic

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26
Q

gram equivalent weight ?
equivalence?

normality?

A

molar mass/n
n = 2 in H2CO3

= mass of compound (g)/gram of equivalent weight (g)

measure of concentration (equivalents/L)
- usually for concentration of H atom

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27
Q

a 1 N (normality) solution will contain a concentration of H ions equal to how many moles/L (molarity)?
2?

1 N of HCl solution, what is molarity?
1 N of H2CO3 solution, what is molarity?

A

1 M
2 M

1 M
0.5 M

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28
Q

what is the conversion between molarity and normality?

A

molarity = normality/n

29
Q

what is percent composition of an element?

A

mass of element in formula/molar mass x 100%

30
Q

differences between combination rxns, decomposition rxns, combustion rxns*****, single-displacement, double-displacement, neutralization rxns?

A

combination - A + B –> C
decomposition - A –> B + C

combustion –> fuel + oxidant –> H20 and CO2

A + BC –> AB + C
AB + CD –> AC + BD

HCl + NaOH –> NaCl + H20 (salt and water)

31
Q

naming polyatomic oxyanions - what does hypo-, per-, -ite, -ate indicatd?

A

hypo - less than ite
-ite (less oxygen)
-ate (more oxygen)
per - more than ate

32
Q

arrhenius equation - rate of reaction according to the collision theory?

A

k = Ae^-(Ea/RT)

A = frequency factor
R = ideal gas constant
T = temperature in kelvins
33
Q

What is rate law? where do you get these exponents?

A

For all forward, irreversible reactions, rate is proportional to concentrations of the reactants, with each reactant raised to some experimentally determined exponent… for example… THE VALUES OF X AND Y ARE NEVER THE SAME AS THE STOICHIOMETRIC COEFFICIENTS!!!!

RATE LAW (MOLARITY/SECOND) – NEVER INCLUDES PRODUCT CONCENTRATIONS
aA + bB  cC + dD , the rate would be

rate = k[A]^x[B]^y

  • overall order of the reaction is the sum of x and y
34
Q

what are the rate laws for zero, first, second and mixed-order rxns?

what do the graphs look like for each?
what is the units of the graph when the graph is linear?
what is k equal to from the graph?

A

zero-order reaction: rate = k[A]0[B]0 = k – rate of formation of C is independent of changes of any reactant, A or B
- increase in concentration of either reactant will not increase rate of rxn (alcohol)
- graph is a straight line
o slope = -k

first-order reaction: rate = k[A]1 or k[B]0 – rate that is directly proportional to only one reactant
- rate of reaction is dependent on concentration of one reactant
o increase concentration, will increase rate of rxn
- [A] vs time graph is a curve
- ln[A] vs time graph is a straight line
o k = -slope

second-order reaction: rate = k[A]1[B]2 or k[A]2 or k[B]2 – rate proportional to either the concentrations of two reactants or to the square of concentration of a single reactant
- [A] vs time graph is a curve
- 1/[A] vs time graph is straight line
o k = slope

mixed-order reactions – non-integer orders (fractions) and rate orders that vary over the course of reaction

35
Q

equilibrium constant?
Q?

what does positive Q mean?
Q = 0?
negative Q?

A

Keq = [C]^c [D]^d/ [A]^a [B]^b = Q (not the constant values)
Q is used to compare where the reaction is compared to equilibrium

Q < 1, ΔG < 0 (spontaneous) – the reaction has not reach equilibrium (greater concentration of reactants than at equilibrium)

Q = 1, ΔG = 0, the reaction is at equilibrium

Q > K, ΔG > 0 (non-spontaneous) – the reaction has exceeded equilibrium

36
Q

When you have a very large negative Keq value, you can assume what when calculating x

A

When you have a very large negative Keq value, you can assume the amount of reactant converted to product is negligible

37
Q

Le Chatelier’s Principle ?

A

Le Chatelier’s Principle – stress is applied to a system, the system shifts to relieve that applied stress

38
Q

le chateliers principle - changes in pressure

  • if pressure increases because increase in volume, the reaction will favor what direction?

changes in temperature

  • if reaction is endothermic (ΔH ___ 0), heat is a ____, meaning reaction will be pushed ______
  • if reaction is exothermic (ΔH ___ 0), heat is a _____, meaning reaction will be pushed _______
A
  1. changes in pressure
    - if pressure increases because increase in volume, the reaction will favor the direction that reacts the most amount of moles -> into the least amount of moles

ex. N2 + 3 H2 -> 2 NH3 - when pressure increases due to increase in volume, the 4 moles of reactants will be pushed forward to produce the smaller two moles of products

  1. changes in temperature
    - if reaction is endothermic (ΔH > 0), heat is a reactant, meaning reaction will be pushed forward
    - if reaction is exothermic (ΔH < 0), heat is a product, meaning reaction will be pushed in reverse
39
Q

what stage of paiget’s cognitive development includes object permanence? (stage and age)

A

sensorimotor (birth - 2 years)

40
Q

what stage of paiget’s cognitive development includes idea of conservation? (stage and age?)

A

preoperational (2-7 years)

41
Q

what stage of paiget’s cognitive development includes symbolic thinking, egocentrinism

A

preoperational (2-7 years)

42
Q

what stage of paiget’s cognitive development includes the ability to think abstractly? (stage and age?)

A

formal operational (11+)

43
Q

PAIGET’S STAGES OF COGNITIVE DEVELOPMENT
information is processed via adaptation which includes assimilation (classifying new information into existing schema) or accommodation (existing schema are modified to fit new information)

  1. sensorimotor
  2. preoperational
  3. concrete operational
  4. formal operational
A

PAIGET’S STAGES OF COGNITIVE DEVELOPMENT
information is processed via adaptation which includes assimilation (classifying new information into existing schema) or accommodation (existing schema are modified to fit new information)

  1. sensorimotor (birth – 2 years) – learns to manipulate environment for own needs
    - primary circular reactions – repetition of body movements that originally occur by chance, but has positive outcome (sucking thumb)
    - secondary circular reactions – repetition of outside of body actions (throwing objects) to get response from environment

object permanence
o marks beginning of representational thought (has mental representations of external objects and events)

  1. preoperational (2 to 7 years) –
  • symbolic thinking (pretend, play make-believe)
  • egocentrism (inability to imagine what other people are feeling)
  • centration (inability to understand concept of conservation)

two slices of pizza will look like more pizza than one large slice of pizza

  1. concrete operational (7- 11 years)
  • understand conservation and perspective of others
  • can’t think abstractly
  1. formal operational (11 +)
    - can think abstractly
44
Q

things that assist decision-making:

a) heuristics ???
- availability heuristic: ?
- representative heuristic: ?

A

things that assist decision-making:

a) heuristics – “rules of thumb”
- availability heuristic: when we try to decide how likely something will be, we pick the one that is easier to think about
- representative heuristic: when we categorize items on the basis of whether they fit the stereotypical category

45
Q
  • ite: ___ oxygens
  • ate: ___ oxygens

ite is changed to -____ acid
ate is changed to -____ acid

A
  • ite: less oxygens
  • ate: more oxygens

ite is changed to -ous acid
ate is changed to -ic acid

46
Q

what is the weak base used on the MCAT?

what is the weak acid used on MCAT?

A 
amines 
acetic acid (CH3COOH)
47
Q

when calculating how many liters of 2 M Ba(OH)2 are needed to titrate a 4 L solution of 6 M H3PO4, what equation do you use?

what is the answer?

A

equivalence point equation: N1V1 = N2V2

N = normality (6 M x 3 H = 18 N)
(2 M x 2 OH = 4 N)
4 L solution

you would need 18 L to titrate

48
Q

when new interactions are stronger than old ones, solvation is ______
- process is preferred at _____ temperatures

when new interactions are weaker than old ones, solvation is _______
- process is preferred at _____ temperatures

A

when new interactions are stronger than old ones, solvation is exothermic
- process is preferred at lower temperatures (take away product, reaction will shift to the right)

when new interactions are weaker than old ones, solvation is endothermic
- process is preferred at high temperatures

49
Q

What two main elements are water soluble and will not affect pH in aqueous solutions?

A

General solubility rules:

  1. ALL salts containing NH4+ (ammonium) and alkali metal (Group 1) cations are WATER SOLUBLE
  2. All salts containing NO3- (nitrate) and acetate (CH3COO-) anions are WATER SOLUBLE

WILL NOT AFFECT PH IN A QUESTION!!!

50
Q

Solubility product constant,?

IP?

A

Solubility product constant, Ksp = [An+]^m[Bm+]^n

where the concentrations of A and B are equilibrium concentrations of the dissociated reactant

same equation- IDENTICAL TO Q

51
Q

if IP is smaller than Ksp? is precipitation or dissolution favored?

If IP > Ksp, reaction is ?

A

reaction has not reached equilibrium yet and the solution is UNSATURATED

  • dissolution

If IP > Ksp, reaction is supersaturated
- Precipitation is favored

52
Q

Complex ions are more stable and have _____ solubility values

A

higher

53
Q

common ion effect

A

Solubility in a solvent that already contains that solute decreases considerably compared to a pure solvent. The reduction in solubility is called common ion effect

    • There is no change in Ksp
54
Q

RAOULTS LAW – as more solute is added to solvent, the vapor pressure of solvent will ______

A

RAOULTS LAW – as more solute is added to solvent, the vapor pressure of solvent will decrease

Pa = XaP’a

Pa = change in pressure
X = mole fraction of A
P'a = absolute pressure
55
Q

boiling point elevation?

A

solute added to solvent will increase boiling point

ΔT=iKbm

i = van Hoffs factor (number of particles into which a compound will dissolve) 
Kb = proportionality constant characteristic of solvent 
m = molality
56
Q

FREEZING POINT DEPRESSION ?

A

FREEZING POINT DEPRESSION – solute added to solvent will decrease freezing point temperature

ΔT=iKfm

57
Q

Density of a gas: ?

A

Density of a gas: p = m/V = PM/RT

58
Q

STP conditions of gas?

A 
STP conditions (273 K and 1 atm and 22.4 L)
Standard conditions (298 K and 1 atm)
59
Q 
volume/temperature/pressure gas equation?
Molar mass (M) of gas equation?

Avagadros principle of gas: ?

Boyles law: ?

Charles law: ?

Gay Lussacs law: ?

A

P1 x V1/T1 = P2 x V2/T2

M = p(STP) x 22.4 L/mol

Avagadros principle of gas: n/V = k, or n1/V1 = n2/V2
- Volume is directly proportional to the amount of moles of a gas at constant pressure and temperature

Boyles law: PV = k, or P1V1 = P2V2
- As pressure increases, volume decreases

Charles law: V/T = k, or V1/T1 = V2/T2
- As temperature increases, volume increases

Gay Lussacs law: P/T = k, or P1/T1 = P2/V2
- As temperature increases, pressure increases

60
Q

Partial pressure of gas?

A

Partial pressure = P = X(Ptotal)

X = mol fraction of gas (mols of gas/total moles of gas)

61
Q

Vapor pressure and condensation reach equilibrium, shown as this equation?

as partial pressure of, for example, oxygen, increases in a vessel, what will happen to its solubility?

A

[A] = Kh x P

solubility will increase!!!

62
Q

Kinetic Energy of Gas – ?
Kb = Boltzmann constant

Average speed of gas molecules, ?

A

Kinetic Energy of Gas – KE = 3/2kT
Kb = Boltzmann constant

Average speed of gas molecules, u = √3RT/M

63
Q
A

All gas particles have same kinetic energy at same temperature regardless of identity, what effect on speed does this have on larger particles vs smaller?
- Larger will move slower than smaller

smaller gases will travel faster than larger gases at the same temperatures

64
Q

Grahams law – the rate of diffusion of gas is directly proportional to

A

Grahams law – the rate of diffusion of gas is directly proportional to the square root of its molar mass, M

65
Q

What is effusion of gas?
what is it proportional to?

what is the equation?

A

What is effusion? Gas moving through a small hole under pressure
- directly proportional to average speed of that gas

Rate of diffusion(speed of gas particle)1/rate of diffusion(speed of gas particle)2 = √M1/√M2

66
Q

in vanderwaals equation of state, which tries to account for the discrepancy in the ideal gas law, what does the a represent and what does the b represent?

A

a - attractive forces between molecules

b- size of molecule

67
Q

FUSION - what is the state changes?
sublimation?
deposition?

A

solid to liquid (like melting)

solid to gas

gas to solid

68
Q

on a phase diagram for thermochemistry, what does the triple point represent?

A

equilibrium between all three phases

69
Q

Bomb calorimeter: constant what?

what does Usystem =

A

Bomb calorimeter: constant volume – no heat is exchanged and no work is being done (because constant volume), so Usystem = - Usurroundings

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