PCAT Chemistry
Atomic Number - ANS the number of protons in the nucleus of an atom, which determines the chemical
properties of an element and its place in the periodic table.
Mass Number - ANS Total number of Protons and Neutrons
Valence Electrons - ANS Electrons farthest from the nucleus
Ion - ANS A positive or negative charge to an atom due to a loss or gain of electrons
Atomic Weight - ANS Weight in grams of one mole of a given element
Mole - ANS 6.022 x 10²³ particles of an element
Isotope - ANS Multiple species of atoms with the same number of protons but different numbers of
neutrons
Angular Momentum - ANS L = (Tangent velocity)(radius)(mass)
L is constant unless disrupted by outside force
Principal Quantum Number - ANS The principal quantum number n represents the relative overall
energy of each orbital, and the energy of each orbital increases as the distance from the nucleus
increases.
,Azimuthal Quantum Number - ANS Second quantum number, designated l. Tells us the shapes of the
electron orbitals
Magnetic Quantum Number - ANS Third quantum number, designated m(ϑ). Tells us the orientation of
the orbitals
(n+1) rule - ANS Used to rank subshells by increasing energy
Periodic Trend for atomic radii - ANS Decreases left to right, increases down
Periodic Trend for electronegativity - ANS Increases left to right, decreases down
3 types of elements - ANS metals - located on the left and middle
nonmetals - located on the right side
metalloids - found along a diagonal line between the other two
Type of Reaction: S + O₂ → SO₂ - ANS Combination Reaction
Type of Reaction: 2 HgO → 2 Hg + O₂ - ANS Decomposition Reaction
Type of Reaction: Zn + CuSO₄ → Cu + ZnSO₄ - ANS Single Displacement Reaction
Type of Reaction: CaCl₂ + 2 AgNO₃ → Ca(NO₃)₂ + 2 AgCl - ANS Double Displacement Reaction
Percent Yield - ANS (Actual Yield/Theoretical Yield) x 100%
,Rank the intermolecular forces from strongest to weakest - ANS Ion-Ion > Ion-dipole > hydrogen
bonding > dipole-dipole > dipole-induced-dipole > London dispersion forces
% Composition - ANS (Mass of X in formula)/(Formula Weight of Compound) x 100%
Used to determine the number of moles present - ANS Mol = (weight of sample (g))/(Molar weight
(g/mol))
For aA + bB → cC + dD: Rate = ? - ANS k[A]^x • [B]^y
x & y must be determined experimentally
Order of Reaction - ANS Determined by adding the exponents of the rate of the equation r = k[A]^x •
[B]^y
Rate of Zero-order reaction - ANS constant rate of r = k
Rate of First-order reaction - ANS proportional to the concentration of one reactant.
rate = k[A] or rate = k[B]
Classic example of First-order reaction - ANS Process of radioactive decay
Calculation for determining a half-life - ANS t½ = ln 2/k = 0.693/k
Rate of Second-order reaction - ANS proportional to the product of the concentration of two reactants
or to the square of the concentration of a single reactant. rate = k[A]², rate = k[B]², or rate = k[A][B]
Activation Energy - ANS The minimum energy of collision necessary for a reaction to take place
, Enthalpy Change - ANS The difference between the potential energy of the products and the potential
energy of the reactants
A negative enthalpy change indicates... - ANS exothermic reaction
A positive enthalpy change indicates... - ANS endothermic reaction
Enzymes - ANS Biological Catalyst
Catalyst - ANS A substance that increases reaction rate without themselves being consumed
How does a Catalyst work? - ANS By lowering the Activation Energy of a reaction
In reversible reactions, such as 2A ↔ B + C, rates = ? - ANS rate(forward) = k(f)[A]²
rate(reverse) = k(r)[B][C]
or, at equilibrium,
k(f)[A]² = k(r)[B][C]
Hund's Rule - ANS States that within a given subshell, orbitals are filled such that there are a maximum
number of half-filled orbitals with parallel spins
Heisenberg Uncertainty Principle - ANS States that it is impossible to determine both the momentum
and position of an electron simultaneously
Rydberg constant - ANS Used to predict the wavelength of light resulting from an electron moving
between energy levels of an atom. When the electron changes from an orbital with high energy to a
Atomic Number - ANS the number of protons in the nucleus of an atom, which determines the chemical
properties of an element and its place in the periodic table.
Mass Number - ANS Total number of Protons and Neutrons
Valence Electrons - ANS Electrons farthest from the nucleus
Ion - ANS A positive or negative charge to an atom due to a loss or gain of electrons
Atomic Weight - ANS Weight in grams of one mole of a given element
Mole - ANS 6.022 x 10²³ particles of an element
Isotope - ANS Multiple species of atoms with the same number of protons but different numbers of
neutrons
Angular Momentum - ANS L = (Tangent velocity)(radius)(mass)
L is constant unless disrupted by outside force
Principal Quantum Number - ANS The principal quantum number n represents the relative overall
energy of each orbital, and the energy of each orbital increases as the distance from the nucleus
increases.
,Azimuthal Quantum Number - ANS Second quantum number, designated l. Tells us the shapes of the
electron orbitals
Magnetic Quantum Number - ANS Third quantum number, designated m(ϑ). Tells us the orientation of
the orbitals
(n+1) rule - ANS Used to rank subshells by increasing energy
Periodic Trend for atomic radii - ANS Decreases left to right, increases down
Periodic Trend for electronegativity - ANS Increases left to right, decreases down
3 types of elements - ANS metals - located on the left and middle
nonmetals - located on the right side
metalloids - found along a diagonal line between the other two
Type of Reaction: S + O₂ → SO₂ - ANS Combination Reaction
Type of Reaction: 2 HgO → 2 Hg + O₂ - ANS Decomposition Reaction
Type of Reaction: Zn + CuSO₄ → Cu + ZnSO₄ - ANS Single Displacement Reaction
Type of Reaction: CaCl₂ + 2 AgNO₃ → Ca(NO₃)₂ + 2 AgCl - ANS Double Displacement Reaction
Percent Yield - ANS (Actual Yield/Theoretical Yield) x 100%
,Rank the intermolecular forces from strongest to weakest - ANS Ion-Ion > Ion-dipole > hydrogen
bonding > dipole-dipole > dipole-induced-dipole > London dispersion forces
% Composition - ANS (Mass of X in formula)/(Formula Weight of Compound) x 100%
Used to determine the number of moles present - ANS Mol = (weight of sample (g))/(Molar weight
(g/mol))
For aA + bB → cC + dD: Rate = ? - ANS k[A]^x • [B]^y
x & y must be determined experimentally
Order of Reaction - ANS Determined by adding the exponents of the rate of the equation r = k[A]^x •
[B]^y
Rate of Zero-order reaction - ANS constant rate of r = k
Rate of First-order reaction - ANS proportional to the concentration of one reactant.
rate = k[A] or rate = k[B]
Classic example of First-order reaction - ANS Process of radioactive decay
Calculation for determining a half-life - ANS t½ = ln 2/k = 0.693/k
Rate of Second-order reaction - ANS proportional to the product of the concentration of two reactants
or to the square of the concentration of a single reactant. rate = k[A]², rate = k[B]², or rate = k[A][B]
Activation Energy - ANS The minimum energy of collision necessary for a reaction to take place
, Enthalpy Change - ANS The difference between the potential energy of the products and the potential
energy of the reactants
A negative enthalpy change indicates... - ANS exothermic reaction
A positive enthalpy change indicates... - ANS endothermic reaction
Enzymes - ANS Biological Catalyst
Catalyst - ANS A substance that increases reaction rate without themselves being consumed
How does a Catalyst work? - ANS By lowering the Activation Energy of a reaction
In reversible reactions, such as 2A ↔ B + C, rates = ? - ANS rate(forward) = k(f)[A]²
rate(reverse) = k(r)[B][C]
or, at equilibrium,
k(f)[A]² = k(r)[B][C]
Hund's Rule - ANS States that within a given subshell, orbitals are filled such that there are a maximum
number of half-filled orbitals with parallel spins
Heisenberg Uncertainty Principle - ANS States that it is impossible to determine both the momentum
and position of an electron simultaneously
Rydberg constant - ANS Used to predict the wavelength of light resulting from an electron moving
between energy levels of an atom. When the electron changes from an orbital with high energy to a
