MCAT Chemistry

atomic mass units
amu or g/mol
metals form ___ oxides
nonmetals form ___ oxides
groups left to right periodic table
alkali, alkaline earth, halogen, noble gases
Zeff/ Effective nuclear charge
charge felt by 2nd electron d/t shielding from 1st e
Zeff trend
increases → & ↓
Atomic radius trend
increases ↓
ionization energy
energy required to pull off one electron from nucleus
Ionization energy trend
increases → (d/t increasing Zeff) & (d/t larger radius @ bottom of periodic table)
Electronegativity def.
Tendency to attract e-
Electronegativity trend
increases → & ↑ (like ionization E)
Which periodic table properties increases → & ↑
E of Ionization, Electron Affinity, Electronegativity
Which periodic table properties decreases from → & ↑
Atomic radius, Metallic character
Empirical formula represents
Ratio of atoms
molecular formula represents
actual # of each atom
-ic vs. -ous
more vs. less (charge or oxygen)
Naming cations
-ic & -ous (less) OR -ium (nonmetal component)
Naming anions
hypo-/ite & -ite, -ate, per-/ate (fewest O to mst)
Naming acids
hydro- & -ic; if have O, no hydro- & use -ic or -ous depending on fewer or more O
ionic crystal
opposite charged held by electrostatic forces
metallic crystal
metal atoms bond together by flowing e-
network covalent crystal
e.g. diamonds. Atoms held by polar & nonpolar bonds
molecular crystal
e.g. ice. Molecules held by intermolecular bonds
Planck equation
Chart for orbitals
e- absorbs energy then moves…
to higher shell
e- emits energy when moves…
to lower shell
# e- in each shell
s=2; p=6; d=10
degenerate orbitals
4s & 3d in Cr & Cu & some other txstn metals
ideal gas law


P-> pressure (atm)

V-> Volume (L)

n-> # mols of gas

R-> constant

T-> Temp (K)

Partial Pressure equation

Pa = XaPtotal

Partial press. of gas in mixture= mol fraction  (mols of gas a / total mols of gas) of that gas times total press.

Total Press. Equation
Ptotal = P1 +P2+P3
Average translational KE
K.E.avg = 3/2RT
For ideal gas, std. properties are:
1 atm, 22.4 L, 1 mol, 0° C (273° K)
When press. increases, K.E. …
Graham’s law (ratio of rms velocities)
v1/v2 = ;m2/;m1
Effusion def.
Gas spreads from high to low press. thru pinhole
Effusion equation
effusion rate1/effusion rate2= ;m2/;m1
Deviations in ideal behavior occurs when…
V decreases (PV=nRT t/f V decreases if P increase or T decreases)
Real gas to ideal gas volume
Vreal ; Videal (b/c ideal gas dsn’t have volume)
Real gas pressure to ideal gas pressure
Preal < Pideal (b/c intermolecular attractive forces stronger t/f slows b/f hit wall)
D = m/v
Rate Law
rateforward = kf [A]α[B]β
1st Order rxn


  • rate=kf[A]
  • [A] decreases exponentially
  • slope= -kf
  • half-life constant

2nd Order Rxn


  • rate= kf[A]2
  • each half-life longer than previous

Law of mass action

K= [C]c[D]d/ [A]a[B]b = Productscoefficients/Rxtntscoefficients

K =? vs. k=?
Equilibrium constant (measured in activity) vs. Rate constant
Rxn Quotient

Q = Productscoeffcients/Rxtntscoefficients

  • For non=equilibrium conditions
  • used to predict direction of rxn

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