Thou Shall Not Forget - AP Chemistry

Stuff you must know to get at least a 3!

When reading measurements from a graduated instrument, what do you do?

You have to estimate by reading in between the graduated markings (can give you more than one sig fig)

Rank measuring devices from least to most precise 

Beaker, graduated cylinder, volumetric flask, burette

How do you find Density? (Use it in stoichiometry to convert mass to volume)

Mass / Volume

What doesn’t change in percent composition by mass?

Pure Compounds

What does a Mass spectroscopy graph depict?

The atomic masses and relative abundances of isotopes

What is coulombs law?

The attractive force between an atom’s protons and electrons. 

• Directly proportional to the number of protons (called Z_eff or effective charge) 

• Indirectly proportional to the square of the distance between the nucleus and electrons 

When an electron is in a higher energy level 

it is farther away from the nucleus & has less coulombic attraction to the nucleus (easier to remove - a lower 1st ionization energy)  

Isotopes of elements have:

the same number of protons and different numbers of neutrons THEREFORE different mass numbers

When moving across a row on the periodic table, the effective charge (Z_eff) increases so ______

the valence electrons are more attracted to the nucleus THEREFORE the atomic radius decreases and ionization energy increases

When reading a PES graph a larger binding energy means —

electrons are closer to the nucleus

In a PES graph what does a higher peak mean?

more electrons are in that sub-level

What doesn’t AP care about?

The order of the electron configuration as long as you have the right number of electrons in each sub-level 

The electron configuration for a Cation you have to:

remove the valence electrons first starting with the highest P-orbital (if there is one) then the highest S-orbital and then so on with the d-orbital

Elements in the same group have:

similar chemical and physical properties 

Metals are on ___   /  Non-Metals are on ____

Left of the ZigZag  /  Right of the ZigZag 

Cations (+) are:

• smaller then their atoms (remove valence electrons)

• further from the nucleus

Anions (-) are:

• larger than their atoms (adding electrons) 

• increases electron - electron repulsion w/o increasing nuclear charge

Percent Yield =

Experimental Mass / Theoretical mass

Percent Error =

( Experimental - Theoretical ) / Theoretical

What are the diatomic elements?

H_2,  O_2,  N_2,  Cl_2,  Br_2,  I_2,  F_2

Covalent bonds are formed between?

Two non-metals sharing electrons

Ionic bonds are formed between?

a metal transfers electrons to a non-metal and the opposite charges attract

The greater the electronegativity  difference between two atoms ____

the more polar the bond becomes

Empirical formula is _____

simplest whole number ratio of moles (or atoms) in the compound

• Percent to Mass : Mass to Mole : Divide by Small, times until Whole! (Rhyme to remember)

The molecular formula for a compound is ____

a whole number multiple of the empirical formula ratio

The amount of a product for a reaction is determined by what?

By limiting the reactant 

How many bonds does Carbon make?

A total of 4 bonds in a compound

Bond angles are what?

• 4 domains = 109.5 deg

• 3 domains = 120 deg

• 2 domains = 180 deg

Hybrid orbitals are what? 

• 4 domains = sp³ 

• 3 domains = sp²

• 2 domains = sp

Asymmetrical molecules = ?

Dipoles DO NOT cancel & polar

Symmetrical molecules = ?

Dipoles cancel & non-polar

What are the types of bonds with sigma, and pi ?

• Single Bond = sigma

• Double bond = sigma + pi bond

• Triple bond = sigma + 2pi bonds

Lattice energy is what? When does the energy increase and decrease?

The energy to break an ionic bond in a compound.

• Lattice energy increases as the ions charge increases

• Lattice energy decreases as the radii of the ions increase

What is the formal charge?

Involves comparing the number of valence electrons an atom has to the number of electrons around the Lewis dot 

How to do the Lewis dot structure?

1. Obey the octet rule

2. Then use formal charge if necessary

3. Extra electrons can go on the central atom (make sure if you have to few electrons double or triple bond)

What are the IMF form the weakest to strongest?

London Dispersion (LD), Dipole to Dipole, Hydrogen Bonding, Ion-dipole

All molecules contain what? When does this IMF get stronger?

London Dispersion forces 

• The LD gets stronger as the molecule is more larger

  • Larger electron could = more LD = more polarizable  

All polar molecules contain what? What makes this IMF stronger?

Dipole - to - Dipole 

• Stronger as the molecule gets more polar

What elements do Hydrogen bonds form? 

F O N! 

• If a FON is one compound has to bonded to another hydrogen that is bonded to a FON

What does boiling and melting point do to an IMF?

IMF will increase if the boiling and melting point increase

What will decrease as the IMF increases?

the vapor pressure & volatility

When molecules have a low melting/boiling points they _____

don’t conduct electricity 

When a molecular solid melts/boils it is ______

the IMF’s between the molecules that break NOT the covalent bonds

SiO_2 (quartz) and Diamonds are COVALENT network solids so they have ____

very high melting/boiling points

Ionic solids have high melting/boiling points so they _____

DON’T conduct electricity as a solid BUT they do conduct when dissolved or (aq)

Metallic bonds are ___

between metals only & ALWAYS conduct electricity

Interstitial alloys are made when what?

A smaller atom fits into the gaps between larger atoms of a metallic crystal 

Substitutional alloys are made when?

The radii of the metals are similar in size and are substituted into the crystal lattice

Gas mixtures are homogeneous, why?

of the constant random motion of particles

Gas are compressible, why?

due to the large spaces between the particles 

Gas pressure is caused by what?

Collisions of particles with the walls of the container. (more collisions = more pressure)

P & V are inversely related, why?

you double the volume of the container which will cut the pressure of gas in half

T & V are directly related, why?

if you heat a balloon, it will expand (Temperature = Volume) 

T & P are directly related, why?

IF you heat a rigid container, the pressure of the grass will increase [T_1(P_1) = T_2(P_2) ]

Ideal gas laws obey what?

Kinetic Molecular Theory

What is the Ideal Gas Law? What are the Units?

PV = nRT 

• Temperature = Kelvins (K)

• Volume = Liters (L)

• Pressure = atm

• R (gas constant) = 0.08206 Latm/molK

One mole of an Ideal Gas = ?

22.4 Liters ONLY AT STP!!!

Gas pressure & number of moles are directly related, why?

if you double the mole of gas in a container, the pressure will double

How do we find molar mass? What are the Units?

Molar Mass = dRT/P 

• d = density (g/L)

• R the gas constant = 0.08206 Latm/molK

The more molar mass a gas has the ____

slower it will move at a given temperature 

Temperature = ?

Average Kinetic Energy (Gases at the same temp have the same average KE)

When collecting a gas by water displacement, what is the equation?

P_total = P_dry gas + P_water vapor

Real gases behave most like what? 

An Ideal gas at high temperatures and at low pressures 

• The more polar a gas is & larger a as is the more is will DEVIATE from ideal behavior 

  • MOREOVER smaller, non-polar gases are most ideal

Filtering separates mixtures based on what?

On differences of particle size, (large particles are trapped on the filter paper. The soluble component foes through the filter paper)

Distillation separates mixtures based on what?

Differences in boiling points (which are determined by IMF) 

Chromatography separates mixtures based on what?

Differences in polarity

In paper chromatography, the component that is most similar in polarity to the ____

“mobile phase” moves p the farthest 

“Like dissolves Like” means what?

Solubility in solvents of differing polarities

Beer’s Law is:

the darker the solution, the more it absorbs light

• Absorbance is directly proportional to concentration of the solute

Compounds can be separated into elements: 

Mixtures can be separated into:

by chemical changes

by physical changes

Mass is conserved during what?

Chemical and Physical changes 

Coefficients of a balanced chemical equation can represent what?

Moles, Molecules, Formula units, or atoms

• NOT MASS!

Acids transfer what?

Protons to bases

Redox reactions = what?

the transfer of electrons 

• OIL RIG

• LEO the lion goes GER

Oxidation numbers are:

H = +1 (except in a hydride, it'll = -1)

O = -2 (except in peroxide, it'll = -1)

Group 1, nitrate, and ammonium are compounds that are:

Soluble!

• Assume others are not!