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MCAT Chem > Bookmark > Flashcards

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1
Q

Root mean square speed

A

u = sqrt(3RT/M) where M=molar mass in kg/mol

A way to measure speed of particles in a gas

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2
Q

All trends on periodic table

A

Electronegativity, ionization energy, e- affinity, electrostatic force, nonmetallic properties inc up a group and to the right of a period
Atomic radius, metallic properties, nucleophilicity inc down a group and to the left of period
Ionic radius is variable, but cations = smaller than anions of same element b/c you lost e-
Good leaving group, electrostatic forces (due to Zeff eqn), and acidity inc down and right; basicity dec down and right

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3
Q

Most NEG change in enthalpy and entropy means?

A

Least change

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4
Q

Least freezing pt depression means?

A

It’ll freeze first

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5
Q

How to inc solid solute solubility? How to inc gas solubility into sln?

A

Only temp can change solubility of solid solute. CHARGED CMPDS (as opposed to neutral cmpds) ARE MORE WATER-SOLUBLE
Gas solubility = directly proportional to pressure of sln and inv proportional to temp of sln

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6
Q

Henry’s Law for gases

A

[A1]/P1 = [A2]/P2 = kH where kH=Henry’s constant (varies depending on type of gas)

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7
Q

Electrostatic force = proportional to?

A

Proportional to (charge of e-*Zeff)/r^2

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8
Q

What happens to energy differences when you inc in energy lvls (ie. inc n)?

A

energy differences become smaller as you inc energy lvls (ex: Ne will have higher energy diff when moving b/w energy lvls than Xe)

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9
Q

How to find energy of e- going b/w energy lvls?

A

E = -RH(1/n^2 initial minus 1/n^2 final)

-RH (Rydberg unit of energy aka energy of e-) is a constant: 2.18E-18 J/e-

Energy of e- b/w energy levels corresponds to EXACT energy of a photon —> can use Planck’s eqn

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10
Q

How to tackle passages

A

1) READ AXES
2) Look for baseline of graphs and take em into account where applicable
3) e- config
4) PAY ATTN TO UNITS
5) clues = mainly in figures, BUT SOME IN TEXT TOO

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11
Q

How to find percent dissociation of acids/bases?

A

([A-]/[HA]) * 100

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12
Q

What happens if you add a strong acid to a sln of weak acid?

A

weak acid won’t ionize as much

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13
Q

LDF

A

When a covalent bond contains slight unequal sharing of e- leading to constant polarization and counter polarization; type of van der Waals force; weakest of intermolecular forces
LDF = only intermolecular force in noble gases, but LDF = present in ALL molec. LDF inc with bigger atoms b/c they have more e- to interact —> more polarizable

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14
Q

Which has greater dipole moment: linear or bent?

A

linear

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15
Q

Linear vs trigonal planar vs tetrahedral vs square planar vs trigonal bipyramidal vs octahedral angles and hybridization

A

180; sp vs 120; sp2 vs 109.5; sp3 vs 90; sp3d2 90,120,180; sp3d vs 90, 180; sp3d2, 6 sigma bonds and no lone pairs

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16
Q

Electrolytes and examples

A

Solutes that allow slns to carry currents; stronger electrolytes can dissolve into more ions —> more conductivity. Strong ex: ionic cmpds like NaCl and KI; highly polar covalent bonds that dissociate when dissolved like HCl; ionic cmpds that can dissolve into greatest amount of cat/anions. Weak ex: molec that ionizes or hydrolyzes weakly in water like acetic acid (basically weak acids) and NH3 (basically weak bases)
Electrolytes prevent charge buildup and inc conductivity in electrolysis; electrolytes should not be [O] or [H]

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17
Q

Factors affecting rxn rate

A

[reactants] (higher conc —> higher collisions, except for zero order rxns); temp (higher temp —> higher collisions); mediums (better in aq slns or polar solvents > nonaq slns; states of matter); catalysts (presence of catalyst —> dec Ea)

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18
Q

Eqns for deltaG vs deltaG0

A

deltaG = deltaG0 + RTlnQ vs deltaG0 = -RTlnK

19
Q

Most neg combustion rate means?

A

Reactants have more energy than products —> less stable

20
Q

In what conditions are real gases diff than ideal gases?

A

at extremely high pressure, low vol and extremely low temp

21
Q

Graham’s PE of diffusion vs effusion. Graham’s law

A

Gases distribute thru vol randomly vs gases under pressure in one box move thru an opening of another; rate of effusion = inv proportional to root of molec wt
r1/r2 = sqrt(M2/M1) where M = molar mass and r = diffusion rate

22
Q

Raoult’s Law

A

P_A = X_A*standardP_A

States that ideal sln behavior = observed when solute/solute, solute/solvent and solvent/solvent interactions are all very similar

23
Q

Buffer slns

A

Mixture of weak acid/base with its salt (ex: CH3COOH & NaCH3COO, NH3 & NH4Cl)

24
Q

Ideal gas amptns aka kinetic molecular theory

A

no intermolecular forces or repulsions b/w gas molec, negligible vol of gas molec when compared to vol of container, collisions = perfectly elastic —> conservation of momentum and energy, gas molec are in continuous random motion, avg KE of gas molec = proportional to absolute temp of gas

25
Q

FYI: ALL ARRHENIUS ACIDS/BASES => B-L ACIDS/BASES => LEWIS ACIDS/BASES BUT NOT ALWAYS THE REVERSE

A

ALL ARRHENIUS ACIDS/BASES => B-L ACIDS/BASES => LEWIS ACIDS/BASES BUT NOT ALWAYS THE REVERSE

26
Q

Thiols = more acidic than alcs

A

Thiols = more acidic than alcs

27
Q

How do halogens inc acidity?

A

if same halogen: alpha position = more acidic than beta, which = more acidic than gamma, etc; also, more halogens bonded –> the greater acidity. if diff halogens: F > Cl > Br > I

28
Q

What happens if you add strong acid to sln of weak acid?

A

weak acid won’t ionize as much

29
Q

n + l rule

A

The lower the sum of n+l —> the lower the energy of subshell (ie. the closer the e- is to the nucleus). If 2 subshells have same n+l value —> the lower n value has lower energy. This rule determines which e-or subshell = closer to nucleus

30
Q

Effective nuclear charge (Zeff)

A

Electrostatic attraction b/w nucleus and outermost e- (aka valence e-); the greater # of p+ in nucleus —> the greater force to pull e- —> e- cloud = closer and binds more tightly to nucleus. HIGHER NET POS CHARGE —> STRONGER Zeff. Calculate it by number of p+ minus number of core e-
Can be affected by shielding effect

31
Q

What/Where are alkali vs alkaline earth metals vs chalcogens vs halogens vs noble gases? What are their characteristics?

A

First group, highly reactive b/c so close to noble gas config (except H) vs second group vs Group 16, Groups of nonmetals and metalloids vs Group 17, highly reactive b/c so close to noble gas config, highly electronegative, diatomic at standard conditions; F and Cl = gas at standard conditions, Br = liq and I = solid at standard conditions vs last group/Group 18, least reactive —> stable, monoatomic at standard conditions

32
Q

How to find formal charge and valence e-?

A 
# ve- in free atom minus # of ve- in bonded atom
Group # on periodic table
33
Q

How to determine higher bpts based on intermolecular forces?

A

Consider all the forces involved (dispersion forces, dipole-dipole, H bonds): Ionic bond = strongest, dispersion forces = weakest; if molec have 1+ type of forces —> higher bpt

34
Q

Law of constant composition. How to find percent composition

A

Any pure sample of cmpd will have identical mass ratio

(Mass of element in formula/molar mass) * 100

35
Q

Law of mass action and properties

A

For a generic reversible rxn, if the system is at equil at a CONSTANT TEMP—> Keq = ([C]^c[D]^d)/([A]^a[B]^b)

Keq = depends on temp
The larger the Keq —> equil is more to the right
Pure solids and pure liq don’t matter in expression
If equil constant of rxn in one direction is Keq, then equil constant of reverse rxn is 1/Keq

36
Q

What kind of rxn vessel is best to do rxns?

A

low thermal conductivity (we want rxn vessel to be insulating), low thermal expansion (we don’t want rxn vessel to expand and break under high temps), high melting pt (we want rxn vessel to w/stand lots of heat if a rxn = exothermic)

37
Q

standard enthalpy of formation for any element in standard state =?

A

= zero

38
Q

What does high molar solubility mean? Why do complex ions inc molar solubility?

A

more solute is dissolved; more ions = produced. Only temp can change solubility of solid solute
Complex ions have multiple pole bonds b/w ligands and central atom —> lots of dipole-dipole interaction —> stabilizes dissolution of complex ion. They also have coordinate covalent bonding

39
Q

Solns = based on enthalpy change. What are ideal solns?

A

When enthalpy change is zero: overall strength to make new bonds is equal to overall strength of breaking old bonds. Ideal sln = determined by Raoult’s Law

40
Q

How to find oxidation state?

A

of nml e- in elemental form - # of bonded e-

41
Q

Bronsted-Lowry acid/base vs Lewis acid/base vs Arrhenius acid/base

A

Proton donor/proton acceptor vs vs e- pair acceptor/e- pair donor vs dissociating to make more H30+/dissociating to make more OH-
FYI: ALL ARRHENIUS ACIDS/BASES => B-L ACIDS/BASES => LEWIS ACIDS/BASES BUT NOT ALWAYS THE REVERSE

42
Q

Half-equivalence pt vs equivalence pt

A

midpoint of buffering region in which half of titrant has been de/protonated thus [HA] = [A-]; pH = pKa vs steepest slope of titration curve, soln = neutralized (you got H2O and salt) –> where conjugate base of the weak acid predominates here; indicator changes color

43
Q

How to change EMF?

A

Change identity of electrode, not the amount; change temp too (this is basically like the equil constants)

MCAT Chem (13 decks)

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