AP Chem Unit 1 Review

atomic mass unit

the mass of an individual atom or 1 mol of atoms is sometimes expressed in this unit?

6.022 x 10^23 particles

How many particles are in 1 mol of a pure substance?

Take number of moles and X by Avad's #

How do you find the number of particles in in 9.30 x 10^-3 mol of Na2CO3?

Multiply number of particles in Na2CO3 and X by mol ratio (2 Na = 1 mol Na2CO3) (X by 2)

How do you find the number of Na atoms in 9.30 X 10^-3 mol of Na2CO3?

(Mass 1 X .RA) + (Mass 2 X .RA)....

How do you find the average atomic mass of an unknown element given mass and relative abundance?

G to moles

Divide by small

Multiply till whole

How do you find the empirical formula of a compound given (g)?

% to g

G to moles

Divide by small

Multiply till whole

How do you find the empirical formula of a compound given (%)?

Divide the molar mass of molecular by empirical's and use the multiple to X the subscripts in emp form

How do you find molecular formula from an empirical given the molar mass of the compound?

Compound + O2 => CO2 + H2O

g CO2 to mol X mol ratio of C:CO2

g H2O to mol X mol ratio of H:H2O

Using moles x & y of CxHy, convert to emp form

How do you find the empirical formula if (g) of C and (g) of H2O formed in a complete combustion?

Find the contaminant w/ a higher % O than in Na2O (higher % would cause an incr in %O).

O MM/Compound MM X 100 = % O

How do you find the contaminant if given % Na, % O but a contaminated sample had a higher % O?

Average mass = (Mass 1 X) + (Mass 2 (1-X))

Solve for X, convert to %

How do you determine the % abundance for 2 isotopes given the average atomic mass?

Electrons are added to the lowest energy subshells first (Increasing E: 1s2s2p3s3p4s3d4p5s)

What is Aufbau's principle?

A cation is SMALLER than the original atom, they lost v.e-. but have the same # of p+ pulling in

How does the ionic radius of an atom change when a cation is made?

A anion is LARGER than the original atom but they have the same # of p+ pulling in; more e- --> more e- REPULSION

How does the ionic radius of an atom change when a anion is made?

It's harder to remove e- b/c closer to nucleus; IE higher

How does a smaller radii affect IE?

It's easier to remove e- b/c further f/m nucleus; IE lower

How does a larger radii affect IE?

F, O, N

What are the most electronegative elements?

Nuclear charge ALWAYS stays the same

IONIC RADIUS changes due to e- repulsions/less of ""

How does nuclear charge differ/stay the same among ions of the same element?

The bigger the difference in electronegativity (the more far apart they are on the periodic table) --> more polar

How does electronegativity relate to bond polarity?

[Ar] 4s^2 3d^6

4s are on the outermost shell, so that's where the v.e.- are. The e- config is:

[Ar] 3d^6

If Fe were to lose two electrons, which subshell/orbital would they be taken from?

Orbitals get 1 e- b4 getting 2 e-

What is Hund's Rule?

The electrons are closer to the nucleus because a nuclear charge would make it harder to remove those e-

What does a high binding energy on a photoelectron spectroscopy mean about those electrons?

Mention nuclear change

What's a general rule when discussing trends across a period?

Mention radius

What's a general rule when discussing trends down a group?

Be: 1s^2 2s^2

B: 1s^2 2s^2 2p^1

p orbitals are further f/m nucleus than in s orbitals --> less energy to remove --> e- in O are easier to remove

Why does B have a lower IE than Be even though IE would normally increase as nuclear charge increases?

(also happens b/t Al and Mg)

N: 1s^2 2s^2 2p^3

O: 1s^2 2s^2 2p^4

O's e- are removed f/m a DOUBLY OCCUPIED p orbital --> e- repulsion --> less en. to remove

Why does O have a lower IE than N even though IE would normally increase as nuclear charge increases?

(also happens b/t P and S)