Gen Chem Review Guides

7/23/2019 Gen Chem Review Guides

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1

Gen Chem Day 1-Atomic and Nuclear StructureAtomic Stucture

Bohr model of the atom

s, p, d, f orbitalsnucleus (protons and neutrons)

electron cloud

atomic # = Z (# of protons)

mass # = N+Z (N = # of neutrons)

isotopesatomic weight

Periodic Table

Organization

Metals vs. non-metalsgroups and periods

Alkali metals, alkaline earth metals, noble gases, halogens, transition metals

Electron ConfigurationsStandard and Noble Gas configurations

Exceptions (Cr, Mo and Cu, Ag, Au)Ions (transition metals too)# valence electrons

Paramagnetic vs. diamagnetic

Quantum Numbers

# Name What? Range

n principal Shell [1]

l azimuthal Subshell (type of orbital) [0(n-1)]

ml magnetic Specific orbital (orientation in space) [-l+l]

ms spin Up or down +1/2 or -1/2

Electron Energy LevelsGround state vs. excited state

Emission vs. absorption spectra


2/15

2

Nuclear ChemistryNuclear Structure and the strong nuclear force

Nuclear symbols

Symbols for , p, n, , and (penetrating power)

Unstable nuclei are radioactive

1) Even numbers of protons and/or neutrons are stable2) N/Z ratio ~1 are more stable (for Z83) below the belt

2) -decay (emission) np N/Z is too high

2) +decay (Positron emission) pn N/Z is too low

3) Electron Capture pn N/Z is too low

3) -decay

Rate of DecayAlways 1

storder (lnN = lnN0 kt)

Half-life (fractions, percents, masses, activities)

Nuclear Binding Energy (total vs. per nucleon)

mass defect (m)

E = mc2 m must be in kg 6.02 x 10

23a.m.u. = 1g

56

Fe has the highest nuclear binding energy per nucleon


3/15

Gen Chem Day 2-Periodic Trends and Bonding

Periodic TrendsAtomic Radius

3

Ionic Radius

Isoelectronic Series

1stIonization EnergyThe energy required to remove an electron

2nd

, 3rd

, 4th

, etc.

Electron AffinityEnergy change associated with gaining an electron

F

He

FClBr

I

Fr

Electronegativity

BondingCovalent (molecular or network solids) non-metal with non-metal

Ionic (ionic crystals) metal with non-metal

Metallic (metallic lattices) metal with metal

Physical PropertiesIonic compounds high m.p. and b.p., brittle

Metallic high m.p. and b.p. (usually), conduct electricity, malleable, ductile

Molecular lower m.p. and b.p.

Molecular Structures

Lewis Dot Symbols (Ex. CH4, CO2, SF4)

Formal ChargesPolar Covalent Bonds

Coordinate Covalent Bonds


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4

Molecular GeometryVSEPR Theory

Hybridization

ElectronDomains

Hybridization Bond Angle Electron DomainGeometry

Non-bondingPairs e

-

Molecular Geometr

2 sp 180 Linear 0 Linear

3 sp2 120 Trigonal planar 0 Trigonal planar

1 Bent

4 sp3 109.5 Tetrahedral 0 Tetrahedral

1 Trigonal pyramida

2 Bent

5 sp3d 90, 120 Trigonal bipyramidal 0 Trigonal bipyramid

1 See-saw

2 T-shaped

3 linear

6 sp3d

2 90 Octahedral 0 Octahedral

1 Square pyramidal2 Square planar

Intermolecular ForcesHydrogen Bonding

F-H, O-H, or N-H bond required in a pure substance

F, O, or N to hydrogen bond with H2O

Dipole-dipole (and ion-dipole, dipole-induced dipole)Intermolecular force for polar molecules

London Dispersion Forces (Van der Waals)

A temporary or transient dipole. All molecules have these and the more surface area, the greater the Londondispersion forces.

Higher Intermolecular Forces lead to higher boiling pts, higher melting pts, higher viscosity, higher surface

tension, but lower vapor pressure


5/15

Gen Chem Day 3-Phases and Gases

PhasesPhysical ChangesPhase Transitions

Endo- vs. Exothermic

Entropy Changes

solid liquid gas

crystallization condensation

deposition

solid liquid gas

fusion vaporization

sublimation

H > 0(Endothermic)

S > 0

H < 0(Exothermic)

S < 0

Calorimetry (q = mcT)Diagram

Phase Diagrams

General H2O CO2

5


6/15

GasesKinetic Molecular Theory

Ideal Gas Assumptions

1) Gas molecules themselves have no volume2)

No intermolecular attractions between molecules (all collisions are elastic)

Kinetic energy T

Characteristics of Gases

Volume (Liters; 1cm3= 1mL)

Temperature (C or K)

Pressure (1atm = 760 torr = 760mmHg)

STP (0C and 1atm) 1 mole gas = 22.4L @ STP

Ideal Gas LawPV = nRT (Works best at low P, high T, and for non-polar gases)

Boyles Law P V

1

Charles Law V T

Avogadros Law V n

Combined gas law22

22

11

11

Tn

VP

Tn

VP

Daltons Law of Partial Pressures PTot= PA+ PB+ PA= APTot

Grahams Law of Effusion1

2

2

1

M

M

r

r

Stoichiometry

Mole to mole ratiosMolar Mass

Avogadros number = 6.02x1023

1 mole gas = 22.4L @ STP

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7/15

Gen Chem Day 4-Solutions and Kinetics

SolutionsVocab.

Solvent, solute, saturated, unsaturated, supersaturated

Concentration

lnLso

molsoluteMolarity

kgsolvent

molsoluteMolality

molestotal_

mol_soluteionmole_fract

Solubility Rules

1) AllGroup I metal, NH4+, NO3

-ClO4

-, and C2H3O2

-(acetate) salts are soluble.

2) MostAg+, Pb

2+, and Hg2

2+salts are insoluble.

Phase Solubility in Liquids Rules1) Solids are more soluble at higher temperatures

2) Gases are less soluble at higher temperatures

3) Gases are more soluble at higher pressures

Colligative Properties

vant Hoff factor

1) Freezing Pt. Depression miKT FF

2) Boiling Pt. Elevation miKT BB

3) Vapor Pressure Depression (Raoults Law) TotalAA PP

4) Osmotic Pressure = iMRT

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8/15

KineticsKinetics vs. Thermodynamics

Rate expressions

2H2O(g)2H2(g)+ O2(g)t

OH

2

][ 2 =t

H

2

][ 2 =t

O

][ 2

Rxn Coordinate Diagram Identify H, Ea, transition state (activated complex), intermediates

Rate Determining Step(slow step)

Catalyst speeds up a reaction by lowering the activation energy by providing an alternate mechanism

(pathway) for the reaction to occur

Rate laws

rate = k[A]x[B]

y

For the reaction 2NO(g)+ Cl2(g)2NOCl(g), the following results were obtained:

[NO]0(mol/L) [Cl2]0(mol/L) Initial Rate (mol/L.s)

0.10 0.10 0.18

0.10 0.20 0.36

0.20 0.20 1.44

What is the rate law for this reaction?

What is the overall rxn order?

What is the rate constant?

Mechanisms

O3O2+ O (rapid equilibrium) or (fast)

O + O32O2 (slow)

What is the intermediate?

What is the rate law?

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9/15

Gen Chem Day 5-Equilibrium and Acid/Base

EquilibriumDefinition of Equilibrium forward rate = reverse rate

Equilibrium constant (mass action ratio)

Keq Meaning

K >> 1 Products favored at eq.

K


10/15

Acids and Bases

Acid Base

Arrhenious H+donor in H2O OH

-donor in H2O

Bronsted-Lowry H+donor H

+acceptor

Lewis Electron acceptor Electron donor

Conjugate Acid / Base Pairs (Amphoteric substances)

Strong acids HClO4, H2SO4, HI, HBr, HCl, HNO3, HClO3

Strong bases - Group 1 metal hydroxides, Ba(OH)2, Sr(OH)2, Ca(OH)2

Binary acid trend

Oxoacid trends

1)

More oxygens, more acidic2) More electronegative heteroatom, more acidic

pH scale

pH, pOH, [H+], [OH

-]; if

you know 1 of the 4, youcan calculate the other 3.

pH of strong acids

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11/15

pH of weak acids

Acid dissociation in water: HA + H2O H3O++ A

-

HAAOH

Ka

3

])[(][ HAKaH

pH of weak bases

Base dissociation in water: A-+ H2O HA + OH

-

A

HAOHKb

])[(][ AKbOH

KaKb= Kw

Neutralization rxns

Neutral

Anions

Cl-

Br-

I-

NO3-

ClO4-

ClO3-

Acidic

AnionHSO4

-

Almost allother

anions are

bases.

Neutral

Cations

Li+

Na+

K+

Rb+

Cs+

Ca2+

Sr2+

Ba

2+

All other

cations are

acidic;

the morepositively

charged, the

more acidic.

Hydrolysis of salts

Buffers

11

][

][log

HA

ApKpH a

Titrations pH at Equivalence Pt

Strong Acid / Strong Base 7

Weak Acid / Strong Base >7

Strong Acid / Weak Base


12/15

Gen Chem Day 6-ThermodynamicsThree laws of thermodynamics

1) Conservation of energy (Energy cant be created or destroyed).

2) For a spontaneous process, the entropy of the universe increases.3) A perfect crystal at 0K has zero entropy.

E = q + w w = -PV

Gas in a piston1)

Transfer of heat (lock piston)

2) Expanding gases cool; compressing gases warm

3) Isobaric (P = 0)

4) Isochoric (V = 0 so w = 0)

5) Isothermal (T = 0 so E = 0)6) Adiabatic (q = 0)

State Functions

Entropy (S)

Phases of matter

S for rxns

S = nSproducts- nSreactants

Enthalpy (H)

Exothermic (H0)

Bond Enthalpies H = Dbroken- DformedBond breaking is endothermic Bond making is exothermic

Whatis H for the following rxn?Bond Enthalpies (kJ/mol)

12

C-H 413C-Cl 328

Cl-Cl 242

H-Cl 431

Enthalpies of Formation

H = nHf,products- nHf,reactantsGiven the following standard enthalpy of formationvalues, calculate the Hrxnof the following reaction:

PCl3(g) + 3HCl(g) 3Cl2(g) + PH3(g) Compound

PCl3(g)

HCl(g)

PH3(g)

Hf (kJ/mol)288.07

92.30

5.40


13/15

Hesss Law C2H4(g) + 6F2(g) 2CF4(g) + 4HF(g) H = ?

H2(g) + F2(g) 2HF(g) H = -537kJ

C(s) + 2F2(g) CF4(g) H = -680kJ

2C(s) + 2H2(g)C2H4(g) H = +52.3kJ

Gibbs Free Energy (G)G0 Nonspontaneous

G=0 At equilibrium

G = nGf,products- nGf,reactants

G = G+ RTlnQ

G= -RTlnKeq

H S

- + Spontaneous at all temperatures

+ - Non-spontaneous at all temperatures

- - Spontaneous at low temperatures

+ + Spontaneous at high temperatures

G = H - TS

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14/15

14

Gen Chem Day 7-Electrochemistry

Oxidation loss of electrons LEO OIL

Reduction gain of electrons GER RIG

Oxidation States

1) Elements in their elemental form are in the zero oxidation state.2) Group 1 metals are +1 and Group 2 metals are +2.

3) Hydrogen is +1 except when bonded to metals (when its 1).4) Transition elements must be determined by context (except Al=+3, Zn=+2, Cd=+2, Ag=+1)

5) The most electronegative elements get their typical oxidation state.6) The last element not assigned balances the charge of the compound/ion.

Balancing Redox Rxns

MnO4-(aq)+ I

-(aq)Mn

2+(aq)+ I2(s)

Oxidizing Agent (Oxidant) species that is reducedReducing Agent (Reductant) species that is oxidized

Elements or compounds are oxidized/reduced whereas only compounds act as reducing/oxidizing agents).

Electrochemical Cells

a) The anode is always the site of oxidation (an ox)b) The cathode is always the site of reduction (red cat)

c) Electrons always flow from anode to cathode

d) Anions flow to the anode and cations to the cathode through the salt bridge

e) In the galvanic/voltaic (spontaneous) cells, the cathode is + and the anode is The signs are the opposite in electrolytic (non-spontaneous) cells.

f) For metal/metal salt solution cells, the cathode gains mass, while the anode loses mass.


15/15

Standard Cell Ptoentials (= cat- an = red+ ox)Remember that the standard hydrogen electrode (SHE) has a potential of 0.00V

Al3+

+ 3e-Al -1.66V

Mn2+

+ 2e-Mn -1.18V

Zn2+

+ 2e-Zn -0.76V

Cr3++ 3e-Cr -0.74V

Fe2+

+ 2e-Fe -0.44V

Co2++ 2e-Co -0.28VNi

2++ 2e

-Ni -0.25V

2H++ 2e

-H2 0.00V

Cu2++ 2e-Cu +0.34V

A

Non-standard cell potentials

15

Qn

EE log0592.0

(Nernst Equation)

Know the qualitative effects that will result in a higher/lower potential.

1) Shift to the right higher potential +1e-A +0.80V

2) Shift to the left lower potential

Reduction potentialsa) What is the strongest oxidizing agent?

b) What is the strongest reducing agent?

c) Which pairs will react spontaneously?

Spontaneous Rxns

G < 0Ecell> 0

Q < K

Electrolysis

Na++ 1e-Na -2.71V 2Br-Br2+ 2e

- -1.07V

2H2O + 2e-H2+ 2OH- -0.83V 2H2O O2+ 4H+4e- -1.23V

a) What are the products of electrolysis of NaBr(l)?

b) What are the products of electrolysis of a solution of NaBr?

Quantitative Calculations

(Amps)(Ts)(MW) = g product (Amps)(Ts) = moles product(n)(F) (n)(F)

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