AP Chemistry Review

Reactions and Stoichiometry

100

A reaction that produces a gas is carried out in a sealed vessel on a balance. What happens to the mass the balance shows, as the reaction proceeds?

It does not change

200

Which of these chlorides is soluble: AgCl, NH₄Cl, Hg₂Cl₂, PbCl₂

NH₄Cl

300

What is the formula of the precipitate formed when ammonium sulfate solution reacts with strontium nitrate solution?

SrSO4

400

How many moles of oxygen gas are required to completely burn 4 moles of methanol (CH3OH)?

2CH3OH + 3O2 gives 2CO2 + 4H2O 6 moles of O2 are required

500

A compound is found to contain 24.8% carbon, 2.0% hydrogen, and 73.2% chlorine with a molecular mass of 96.9 g/mol.  What is the molecular formula?

C₂H₂Cl₂

Electronic Structure and Periodicity

100

What is Coulomb's law?

Like charges repel; opposite charges attract.

200

What are the names of the two bonds resulting from overlapping atomic orbitals?  What is the rule for counting them?

Sigma and Pi Bonds: Every covalent bond has a sigma bond, double bonds have a pi & sigma bond, triple bonds have two pi and 1 sigma bond.

300

Out of C, Si and P: which has the highest electronegativity?

C

400

What is the correct explanation for why a sulfide ion has a larger radius than a sulfur atom?

Increased electron-electron repulsion in the outer shell

500

What is the molecular geometry, electron geometry, bond angle(s), and polarity of ClF₃?

Square Pyramidal, Octahedral, 90°, Polar

Thermochemistry

100

What happens to the enthalpy of a system during an endothermic process?

It increases!

200

What type of particle motion do microwaves and IR cause?

Microwave: Rotation

IR: Bending, symmetric and asymmetric stretching

300

What is the sign of "delta H of vaporization" and how does its magnitude compare to "delta H of fusion" for a typical substance?

The sign is positive (endothermic) and it is generally greater than "delta H of fusion"

400

How do you calculate the enthalpy change of a reaction, using the standard enthalpy change of formation of the reactants and products of the reaction?

Enthalpy change of reaction = sum of standard enthalpy change of formation of products - sum of standard enthalpy change of formation of reactants

500

A salt dissolves in water in a calorimeter and the forces formed are weaker than those broken. If the calorimeter does not insulate completely, how does the enthalpy change measured compare to the true enthalpy change for the dissolving? (give the sign of the enthalpy change and how the experimental value deviates from true)

The experimental enthalpy change is positive and smaller in magnitude than the true value

Bonding

100

What is the missing word? Breaking bonds __________ energy

"requires" or "needs"

200

List the 4 main IMFs in order from weakest to strongest: Dipole-Dipole, Hydrogen Bonding, Ion-Dipole, LDFs

LDFs, Dipole-Dipole, Hydrogen Bonding, Ion-Dipole

300

Why are metals conductive as a solid?

Metal cations are held together by a delocalized "sea" of valence electrons.

400

State the 4 qualities of an ideal gas

Gas particles have...

- negligible volume.

- Equal size and no IMFs

- random motion

- elastic collisions with no energy loss

500

Which of these species displays resonance? phosphorus pentachloride, phosphate ion, tetraphosporus decoxide, carbon monoxide

phosphate ion

Miscellaneous

100

What is steam?

Condensed water vapor

200

What is the constant R equal to? WITH UNITS!

0.08206 (L*atm)/(mol*K)

300

What is the function of enzymes?  Why are they important to living organisms?

- Act as a catalyst by lowering the E_a of reactions

- Work to manipulate the bonds of the substrate (can either break or form bonds)

- Help organisms maintain order and control of millions rxns occurring at once

400

Which net ionic equation below represents a possible reaction that takes place when a strip of magnesium metal is oxidized by a solution of chromium (III) nitrate?

A. Mg(s) + Cr(NO3)3(aq) → Mg2+(aq) + Cr3+(aq) + 3NO3-(aq)
B. 3Mg(s) + 2Cr3+ → 3Mg2+ + 2Cr(s)
C. Mg(s) + Cr3+ → Mg2+ + Cr(s)
D. 3Mg(s) + 2Cr(NO3)3(aq) → 3Mg2+(aq) + 2Cr(s) + NO3-(aq)

B

500

2N₂O₅ (g) -> 2N₂ (g) + 5O₂ (g)

This first-order rxn decomposes with a half-life of 7 minutes at 230°C.

If N₂O₅ is added to an evacuated flask to a pressure of 800 torr at 230°C, what is the total pressure of the flask after 14 minutes?

2,300 torr