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CHE 107 (Exam 3)
Chp. 15.9+, 16, 18, -19.3
41
Chemistry
Undergraduate 2
04/08/2009

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Term
Acid strength
Definition

-measured by its tendency to ionize

(more polar = more electronegative)

 

-the stronger the bond, means the weaker the acid

(harder to breakup, therefore WA)

Term
Hydrohalic Acids
Definition

Includes: F, Cl, Br, I

 

Strength increases as move down column

F > Cl > Br > I

Term
Oxalic Acids
Definition

-Must have: H, O, and Z (central atom)

-=Z - O - H

 

-Acid strength increases with electronegativity of central atom

 

-Acid strength increases as oxidation number increases

(more O atoms = more acid strength; draws electron density away from H making it more polar and therefore more electronegative)

 

-Acid strength increases as move across period

Term
Oxidation Numbers
Definition

1. Free elements = 0

(H2, Na, Be, K, P4 = 0)

 

2. Ions = their charge

(Li+=+1, Ba2+=+2, O2-=-2)

 

3. Oxygen is normally -2 in most compounds, but in H2O2 and peroxide ion =-1

 

4. H is +1, except when with metals in binary cmpds, then is -1

(LiH, NaH, CaH2)

 

5. F = -1, but all other halides = their charge #

 

6. Neutral molecule should =0. Charged molecules should add up to their overall charge

(NH4+ = N(-3) and H4(+1)

 

7. Can be integers

(superoxide O2-=-1/2)

Term
Salt Hydrolysis:
Definition

The reaction of an anion or a cation of a salt, or both, with water

 

-Salts that produce neutral solutions

NaNO3 --> Na+ + NO3-

Na+ neither donates or accepts H+

No3- is CB of SA (HNO3) and therefore no hydrolysis

 

-Salts that produce basic solutions

CH3COONa --> CH3COO- + Na+

Na+ neither donates or accepts H+

CH3COO- is CB oF WA (CH3COOH) and therefore wants to gain H+, making overall basic

 

 

-Salts that produce acidic solutions

NH4Cl --> NH4+ +Cl-

Cl- is CB of SA (HCl) and therefore no hydrolysis

NH4+ is CA of WB (NH3) and therefore makes acidic---able to donate H+ to Cl-

 

Term
Percent Hydrolysis
Definition

%H = [C]hydrolyzed at equilibrium  x 100%

[C]initial

Term
Basic, Acidic, Amphoteric Oxides
Definition

Basic: Li, Na, K, Rb, CS, Mg, Ca, Sr, Ba, In, Tl

(all 1A, all 2A except Be, and In2O3 & Tl2O3)

 

Acidic: B, C, Si, Ge, N, P, As, Sb, Bi, S, Se, Te, Po, O, Cl, Br, I, At

(all 5A, all 6A except O, all 7A, only B on 3A, top 3 on 4A)

 

Amphoteric: BeO, Al2O3, Ga2O3, SnO2, PbO2

 

 

Term
Lewis Acid:
Definition

a substance that can accept a pair of electrons

 

Ag+ + 2NH3 <---> Ag(NH3)+2

LA        LB

 

 

Term
Lewis Base:
Definition

a substance that can donate a pair of elctrons

 

Ag+ + 2NH3 <---> Ag(NH3)+2

LA        LB

Term
Salt:
Definition

an ionic compound formed by the reaction between an acid and a base

 

 

Term
Neutral salt if...
Definition

-Cation is alkali metal or alkaline earth metal

(ion can neither accept or donate a proton because already has + charge)

 

-Anion is CB of SA

(CBs of SAs ahve "no appreciable strength")

Term
Common Ion:
Definition

2 solutes dissolved in a solvent that contain the same ion

 

HF +H2O <---> F- + H3O+

 

NaF ---> Na+ + F-

Term
Common Ion Effect:
Definition

the shift in equilibrium caused by the addition of a compound having an ion in common with the dissolved substance

 

*common ion raises pH of acid soln.*

Term
Buffer Solution:
Definition

a solution that resists change to pH

(consists of WA or WB and it's conjugate salt)

 

*buffer is a specific type of "common ion effect" problem and therefore H-H equation can be used to calculate pH*

 

 

Term
At FINAL line of ICF...
Definition

-Remainder: SA or SB

Procedure: calculate pH directly from molarity of SA or SB

(found in titrations)

 

-Reamainder: WA or WB

Procedure: write substance's equilibrium with water and fill out ICE table

(found in titrations)

(at equivalence point)

 

-Remainder: CB/CA pair

Procedure: use H-H equation

Term
Indicator
Definition

a substance which changes color with pH

 

-usually a weak organic acid

-has 2 distinctly different colors in ionized and nonionized form

 

HIn  + H2O <---> In- + H3O+

purple                       red

Term
Q and Ksp
Definition

Q < Ksp

unsaturated

can dissolve more

favors products (shift R more)

 

Q = Ksp

saturated

equilibrium point ([C]0 = [C]e)

 

Q > Ksp

supersaturated

wants to ppt out more

favors reactant (shift L more)

Term
Molar Solubility:
Definition

# mol of solute in 1L of a saturated solution (mol/L)

 

 

(s)

Term
Solubility
Definition
# grams of solute in 1L of a saturated solution (g/L)
Term
If anion of salt is the CB of WA...
Definition

Then solubility increases with decreasing pH

(i.e. added acid)

Term
Spontaneous Reaction:
Definition

reaction will occur under a certain set of conditions

 

examples:

-water in a freezer will freeze

-diamonds will convert to graphite (no matter the rate of reaction)

Term
Entropy:
Definition

direct measure of randomness or disorder of a system

 

-larger disorder = larger value of S

 

-as temperature increases, entropy increases

(molecules morve more rapidly with added heat; entropy of gas is much larger than solid and liquid)

Term
Standard Entropy:
Definition

absolute entropy of a substance at 1 atm and 25o

Celsius

 

Ssolid < Sliquid << Sgas

Term
Processes that lead to increase in entropy of a system
Definition

1. melting

 

2. vaporization or sublimation

vaporization: liquid --> gas

sublimation: solid --> gas

deposition: gas --> solid

 

3. dissolving a molecular compound

 

4. raising the temperature of a system

Term
Second Law of Thermodynamics:
Definition

the entropy of the universe increases in a spontaneous process and remains unchanged in an equilibrium process

 

spontaneous:

ΔSuniverse = ΔSsystem + ΔSsurroundings > 0

*if process has +ΔSuniverse, then will be spontaneous)

 

equilibrium:

ΔSuniverse = ΔSsystem + ΔSsurroundings = 0

 

 

Term
Endothermic & Exothermic
Definition

ΔSsurroundings =          1

                                  -ΔHsystem

 

 

endothermic reaction

-ΔH

+ΔS

 

exothermic reaction

Term
Third Law of Thermodynamics
Definition
entropy of a perfect crystalline substance is 0 at absolute zero of temperature
Term
Gibbs Free Energy
Definition

ΔG = ΔH -TΔS

 

ΔG < 0: spontaneous

 

ΔG > 0: spontaneous in reverse direction

 

ΔG = 0: equilibrium

0= ΔH -TΔS

T = ΔH      

ΔS

Term
Standard Free Energy of Formation:
Definition

the free energy change that occurs when 1 mol of compound is synthesized from its elements in standard states

 

ΣΔGof(products) and ΣΔGof(reactants)

Term
Standard Free Energy of Reaction:
Definition

standard enthalpy of formation of any element in its stable form is 0

 

ΔGorxn

Term
ΔGo vs. ΔG
Definition

ΔGo: ΔG at standard state (only 1 set of conditions)

 

ΔG: when leaves standard state (ex. at equilibrium)

Term
ΔG = ?
Definition

ΔG = ΔGo + RTlnQ

 

when ΔG = 0:

0 = ΔGo + RTlnK

 

ΔGo = -RTlnK

 

Term
Electrochemistry:
Definition

branch of chemistry dealing with interconversion between electrical and chemical energy

 

-energy is released by spontaneous redox reaction

 

-energy is used to cause nonspontaneous reaction to occur

Term
Redox Reactions
Definition
reactions involving transfer of electrons from one substance to another
Term
Ion-Electron Method:
Definition
a special procedure to balance redox reactions
Term
Galvanic Cell:
Definition

experimental apparatus for generating electricity through use of a spontaneous redox reaction

 

(aka voltaic cell)

Term
Amp vs. Cell Voltage
Definition

amp: # of electrons that move through a wire

 

cell voltage: "zing" speed on electrons as move through wire (how much force throw ball)

Term
Salt Bridge:
Definition

contains an inert (neutral) electrolytic solution that allows the charges on both sides to stay balanced

 

-electrons leave from L side and as [cation] increases, anions enter to balance

 

*ALWAYS: anode ---> cathode

Term
Standard Reduction Potential
Definition

the voltage associated with a reduction reaction at an electrode when all solutes are 1M and all gases are 1atm

 

(Eored)

Term
Standard Oxidation Potential:
Definition

the voltage associated with an oxidation reaction at an electrode when all solutes are 1M and gases are 1atm

 

(Eoox)

Term
Standard Cell Potential:
Definition

sum of standard oxidation potential and standard reduction potential

 

Eocell = Eoox + Eored

 

(Eocell)

(standard emf)

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