AP Chemistry - AP Exam Review

Flashcards imported from Mrs. S

How do you calculate the empirical formula?

Convert % to mass → mass to moles → divide by smallest value → multiply until whole.

What is the molecular formula of a compound?

A whole number multiple of the empirical formula.

What do complete hydrocarbon combustion reactions form?

CO2(g) and H2O(g).

What happens to C and H atoms during combustion analysis?

C atoms end up in CO2 (1:1 ratio), H atoms end up in H2O (2:1 ratio).

What are isotopes?

When an element have the same number of protons but different numbers of neutrons.

What do mass spectroscopy graphs show?

Each isotope's atomic mass and relative abundance.

What happens to an electron at a higher energy level?

It is farther from the nucleus, has less Coulombic attraction, and requires less energy to remove.

What are the periodic trends when moving across a period?

Zeff increases, atomic radius decreases, ionization energy increases, electronegativity increases.

What are the periodic trends when moving down a group?

Zeff decreases, atomic radius increases, ionization energy decreases, electronegativity decreases.

What does a PES graph indicate?

Higher peaks mean more electrons in that sublevel; larger binding energy means electrons are closer to the nucleus.

How do you write electron configuration for an atom?

Move across the periodic table: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6.

What is the exception in writing electron configuration for Cr and Cu?

Electrons move from the 4s orbital to half-fill (Cr) or fill (Cu) the 3d orbital.

How do you write electron configuration for a cation?

Remove valence electrons first, starting from the highest energy level.

What do elements in the same group have in common?

They have similar chemical and physical properties.

How do cations compare to their parent atoms?

Cations are smaller due to the removal of valence electrons and increased Zeff.

How do anions compare to their parent atoms?

Anions are larger due to gained electrons and increased electron-electron repulsions.

What forms covalent bonds?

Covalent bonds form between two nonmetals sharing electrons.

What forms ionic bonds?

Ionic bonds form when a metal transfers electrons to a nonmetal.

How does electronegativity difference affect bond polarity?

The greater the difference, the more polar the bond becomes.

What are the bond angles for different electron domains?

4 e- domains = 109.5°, 3 e- domains = 120°, 2 e- domains = 180°.

What are hybrid orbitals for different electron domains?

4 e- domains = sp3, 3 e- domains = sp2, 2 e- domains = sp.

How can you determine molecular polarity?

Consider bond polarity and molecular symmetry.

What is the bond formation for single, double, and triple bonds?

Single bond = 1 sigma; Double bond = 1 sigma + 1 pi; Triple bond = 1 sigma + 2 pi.

What is lattice energy?

The energy to break an ionic bond in a compound.

What does formal charge compare?

The number of valence electrons in an atom to the number of electrons around it in the Lewis structure.

What are the properties of molecular solids?

They have low melting/boiling points and do not conduct electricity.

What are the properties of ionic solids?

They have high melting/boiling points and do not conduct electricity as a solid.

What are the properties of covalent network solids?

They have very high boiling/melting points.

What happens when molecular solids melt or vaporize?

IMFs between the molecules are overcome, not covalent bonds.

What causes gas pressure?

Collisions of particles with the walls of the container.

How are P and V related?

They are inversely related; doubling the volume reduces pressure by half.

How are T and V related?

They are directly related; heating a balloon causes it to expand.

How are T and P related?

They are directly related; heating a rigid container increases gas pressure.

What is the ideal gas law?

PV=nRT

What is the volume occupied by one mole of an ideal gas at STP?

22.4 L/mol

How are gas pressure and moles related?

They are directly related; doubling the moles doubles the pressure.

What is the formula for molar mass in terms of density, R, and pressure?

Molar Mass = dRT/P

What does temperature represent in terms of kinetic energy?

Temperature is the average kinetic energy of gas molecules.

What is the relationship between molar mass and velocity at the same temperature?

Higher molar mass results in lower velocity.

What is partial pressure in a gas mixture?

It is proportional to the number of moles of each gas present.

What is the equation for total pressure when collecting gas by water displacement?

Ptotal = Pdry gas + Pwater vapour

Under what conditions do real gases behave most like ideal gases?

At high temperature and low pressure.

What can separate compounds into elements?

Chemical changes.

How does filtering separate mixtures?

Based on differences in particle size.

What is the principle behind distillation?

It separates mixtures based on differences in boiling point.

What does chromatography separate based on?

Differences in polarity.

In paper chromatography, which component moves the farthest?

The component most similar in polarity to the mobile phase.

What happens to the % composition by mass of a pure compound in a mixture?

It changes.

What remains constant in a dilution?

The moles of solute.

What is the Beer-Lambert law?

Absorbance is proportional to concentration.

What type of radiation is associated with molecular rotational transitions?

Microwave radiation.

What type of radiation is associated with molecular vibrational transitions?

Infrared radiation.

What type of radiation is associated with electronic energy level transitions?

Ultraviolet/visible radiation.

What is the correct way to read a volume of liquid?

Report all certain digits plus one uncertain digit.

Which measuring device is the most precise?

Burette.

What are the diatomic elements?

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

How is % yield calculated?

% yield = (experimental/theoretical) x 100%.

How is % error calculated?

% error = (experimental - theoretical)/theoretical x 100%.

What determines the amount of product formed in a reaction?

The limiting reactant.

What is conserved during chemical and physical changes?

Mass.

What suggests a chemical process has occurred?

Breaking and/or forming of chemical bonds.

What type of reaction involves the transfer of protons?

Acid-base reaction.

What type of reaction involves the transfer of electrons?

Oxidation-reduction (redox) reaction.

What is a precipitation reaction?

Formation of an insoluble ionic compound from two aqueous solutions.

What factors affect the rate of a reaction?

Collision orientation, activation energy, concentration, surface area, pressure, and temperature.

What is the half-life formula for a first-order process?

t1/2 = 0.693/k.

What happens to the half-life of a first-order reaction regardless of initial concentration?

It remains constant.

What does a taller activation energy hill indicate?

A slower reaction.

What dictates the speed of a reaction?

The slow step (rate-determining step).

What happens to intermediates in reaction mechanisms?

They are produced in one step and consumed in a later step.

What happens to catalysts in reaction mechanisms?

They are consumed in one step and produced in a later step.

What defines exothermic reactions?

The system releases heat; surroundings' temperature increases.

What defines endothermic reactions?

The system absorbs heat; surroundings' temperature decreases.

What is bond enthalpy?

The energy required for bond breaking.

What happens in an exothermic process?

Bonds formed in the products are stronger and more stable than the reactant bonds.

How do you calculate ΔHrxn using bond enthalpy?

ΔHrxn = bonds broken − bonds formed.

How do you calculate ΔHrxn using enthalpy of formation?

ΔHrxn = ΔHproducts − ΔHreactants (multiply by coefficients).

What does Hess's Law state?

ΔHrxn = ΔH1 + ΔH2 + ΔH3; if coefficients are doubled, ΔH is doubled; if a reaction is reversed, the sign for ΔH is reversed.

What is the equilibrium constant expression?

Keq = [products]x/[reactants]y.

What types of species appear in an equilibrium expression?

Only (aq) and (g) species appear.

What does a large Keq indicate?

More products at equilibrium (K > 1).

What does a small Keq indicate?

More reactants at equilibrium (K < 1).

How does reversing a reaction affect Keq?

Keq becomes 1/Keq.

What is Le Chatelier's Principle?

The direction of shift depends on Q; if Q > Keq, the reaction shifts to form more reactants.

What happens if Q < Keq?

The reaction shifts to form more products.

Do catalysts affect the position of equilibrium?

No, catalysts do not shift the position of equilibrium.

How does pressure affect equilibrium?

Changes in pressure can shift equilibrium if the number of gas molecules differs on each side.

What is molar solubility (S)?

The concentration of species in a saturated solution at equilibrium.

What is the solubility product for a 1:1 ion ratio?

Ksp = S².

What is the solubility product for a 2:1 ion ratio?

Ksp = 4S³.

What is the solubility product for a 3:1 ion ratio?

Ksp = 27S³.

What is the solubility product for a 3:2 ion ratio?

Ksp = 108S⁵.

What does a larger S value indicate?

The salt is more soluble.

What happens if Q > Ksp?

A precipitate forms.

Which ions are 100% soluble in water?

SNAP ions: Na+, K+, NH4+, and NO3-.

What is the pH range for acids?

pH < 7.

What is the pH range for bases?

pH > 7.

What is the pH of pure water at 25°C?

pH = 7.

What do acids do in terms of H+?

Acids donate H+.

What do bases do in terms of H+?

Bases accept H+.