Chem Exam Review Flashcards

1
Q

What is the Octet Rule?

A

A full valence = 8e- (except helium-only2). Elements gain/lose e- to achieve an octet, becoming ions.

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2
Q

What are Cations/Anions?

A

Cation=positive ion

Anion=negative ion

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3
Q

What is Ionization Energy

A

The quantity of energy required to remove an electron from an atom or ion in gaseous state.

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4
Q

How do you write an I.E. equation?

A

Lewis Symbol + I.E. -> [Cation]_++_e-

Ex. Li• + I.E. -> [Li]1+ + 1e-

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5
Q

What is Electron Affinity?

A

The quantity of energy change when an electron is added to the valence shell of an atom in gaseous state.

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6
Q

How do you write an E.A. equation?

A

Lewis Symbol + #e- -> [Anion]_- + E.A.

Ex. S•(x6) + 2e- -> [S•(x8)]2- + E.A.

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7
Q

What does Isoelectronic mean?

A

“Same electron configuration as”

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8
Q

What are Isotopes?

A

Atoms of an element with same # p+ and e- but differ in #no

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9
Q

What is Average Atomic Mass? What are the unit?

A

Average of the masses of all the isotopes of an element. Units are “u” (atomic mass units)

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10
Q

How do you calculate AverageAtomicMass?

A

AAM= mass(%abundance)+mass(%abundance)

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11
Q

Half Life & Equation

A

Time taken for half original #atoms to decay.

M<sub>r</sub>=M<sub>o</sub>x(½)<sup>#of half lives</sup>
#half lives = total time / t (½)
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12
Q

What are the two factors that affect attraction for valence e-

A

Number of Orbits

Nuclear Charge

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13
Q

of Orbits

A

Row#(period)=#of Orbits

Electrostatic attraction between valence e- and the nucleus decrease as # of orbits increase (e- are farther away from protons)

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14
Q

Nuclear Charge

A

NC=# of protons in nucleus

Increases to the right of a period

Larger #= stronger electrostatic attraction

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15
Q

Ionic Radius Trend

A

Cations are smaller than their neutral atom

Anions are larger than their neutral atom

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16
Q

Multiple Ionization Energies Trend

A

First I.E.- energy to remove first e- (weakest hold)

Second I.E.- energy to remove second e- (more than 1st I.E.-protons pulling on less e-)

Third I.E. energy to remove third e- (more than first two-protons pull on less e-)

17
Q

What is Metallic Character?

A

The ability to lose e-. Lower I.E. = more metallic

18
Q

Non-Metallic Character

A

Higher E.A. = more reactive non-metal (ability to attract e-)

19
Q

Electronegativity

A

EN is a measure of how well an atom can attract a shared pair of e- around it’s nucleus.

20
Q

Trends in the Periodic Table

A

Down a group : Atomic radius and ionic radius increases, Metallic Character increases,

Across a period : Ionization Energy increases, Electron Affinity increases, Non-Metallic Character increases, Electronegativity (EN) increases

21
Q

Expanded Octet

A

Elements in third row [and down] can be surrounded by more than 8 e- in order to minimize formal charge.

22
Q

Guide to Balancing

A
  1. Metals
  2. Polyatomic ion groups
  3. Non-metals
  4. Hydrogen and oxygen
23
Q

Sig Figs & Zeros

A
  • Leading zeros don’t count
  • Captive zeros always count
  • Trailing zeros count

If x and / take least # of sig figs

If + and - take least # of decimal places

24
Q

Law of Constant Composition

A

Any given compound has the same composition anywhere.

Adding or removing atoms changes compound into completely different substance.

H2O is always 88.9% O and 11.1% H

25
Percent Composition
% by mass of each element in a compound. (always the same no matter how large the sample) %C = mass[Element] / total mass [Compound] x 100
26
Dissociation Equation
Shows soluble ionic compound breaking into ions in solution. Ex. NaCl(s) -\> Na+(aq) + Cl-(aq)
27
Dissolving Molecular Compounds
Most dissolve as molecules (except acids). Int.molec.forces are broken, bonds aren't. Therefore most molec.substances (except acids) are non-electrolytes [no mobile ions].
28
Solvents / Solubility Rules
Rule: Like dissolves like. Polar solvents dissolve polar molecules due to DD forces Non-polar solvents dissolve non-polar molecules due to LDF \*H2O - polar, C8H18 (gasoline) - non-polar\*
29
Percent Concentration
v/v \*units must be the same (5ml/100ml) m/v \*units are g/ml (4% = 4g/100ml) m/m \*units must be the same (2g/100g)
30
Low Concentrations
Parts per mil. - ppm: cppm= m/m x106 Parts per bil. - ppb: cppb= m/m x109 Parts per tril. - ppt: cppt= m/m x1012
31
pH
Power of Hydrogen - indicates amount of H3O+ in a solution One unit of pH change means 10x change in H3O+ concentration Ex. pH of 5 is 10x more acidic than pH of 6
32
How to calculate [H3O+] / pH
[H3O+] = 10-pH If [H3O+] is _#_x10-_mol/L = -log_#_x10-_ Ex. 2.3x10-2mol/L -\> -log2.3x10-2 = 1.6pH \*square brackets mean concentration\*
33
pOH
pOH=7 [OH1-] = 10-7mol/L
34
Absolute Scale of Temperature
Celcius Kelvin 100oC 373K 0oC 273K -273oC 0 K
35
Dalton's Law of Partial Pressure
Ptotal = P1 + P2 + P3 ... \*Collecting gas over water includes water vapour, therefore the partial pressure of water must be subtracted.
36
SATP and STP Values
_SATP__STP_ T : 25oC = 298K 0oC = 273k P : 100kPa 101.3kPa n : 1 mol 1 mol V : 24.8L 22.4L
37
Percent Ionization
%ionization (p) = [H3O+] / [Acid] x100