quiz 2 goals

8/13/2019 Quiz 2 Goals

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CHEM 215 Quiz 2 Review 11/16/2013

Remember:While all the information listed here is equally important, it is not possible

to test you on all this material for the exam. But, the course material that is not includedon exam II will have a higher likelihood of appearing on the final exam.

Chemical Equilibrium (Chapter 6)

Main Goals:

A. Understanding Basic principals of Chemical Equilibrium:

a. What is equilibrium?

i. All equilibria must be satisfied

ii. Only a single concentration for each component regardless of thenumber of chemical equilibria

b. What is equilibrium constant?

i. What does the magnitude of the equilibrium constant say about a

reaction?ii. How to deal with pure solids, liquids and gases.

c. Manipulating equilibrium constantsi. Adding chemical reactions

ii. Inverting chemical reaction

d. Factors that determine if a reaction proceeds spontaneouslyi. Enthalpy

a) Terms: Endothermic and exothermic

ii. entropy

iii. free energyiv. thermodynamic vs. kinetic

e. Relationship between equilibrium constant and free energyi. Two forms of equation

a) In terms of G

b) In terms of H,S and T

f. Le Chteliers Principaland chemical equilibriumi. Reaction quotient

ii. Impact of temperature

iii. Common ion effectg. Types of chemical equilibrium

i. Solubility (Ksp)

ii. Complex formation (Kf)

iii.

Acid-basea) Definitions:

1. Lewis acid & base

2. Protic acid & base

3. Bronsted-Lowry acid & base

4. Salt

5. Conjugate acids and bases

6. Autoprotolysis


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7. pH

8. pK

9. strong acid and bases

10. weak acid and bases

11. polyprotic acids and bases

h.

Relationship between Ka, Kband Kw

Titrations (Chapter 7)

Main Goals:

B. Understanding the Titration process:

a. What are the basic steps and requirements in a volumetric titration?

i. Terms: titrant, analyteb. What is the end-point?

i. How an end-point is measureda) Spectrophometricb) Electrode

c) Volhard

d) Fajansc. What is the equivalence point?

d. What is the important difference between the end-point and equivalence

point?

i. How is this difference corrected for?a) Blank titration

b) Back titration

e. What is standardization of a titrant?i. How does standardization differ from titration?

C. Understanding the titration curve:

a. What are the regions of the curve?

b. How to predict a titration curve from the equilibrium constant.i. Using pX

c. Relationship between titration curve and equilibrium constant

d. Titration curve of mixtures

Activity (Chapter 8)

Main Goals:

D. Understanding the theory of activity:

a. What is ionic strength?i. How is it calculated?


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b. What is hydration?

i. What determines the size of the hydration sphere?c. What is the ionic atmosphere?

i. How is this related to ionic strength?

d. How is activity related to hydration shell and ionic atmosphere?

e.

How is activity related to ionic strength?i. Relationship to common ion effect

f. How is activity related to concentration?

i. What is the effect on an equilibrium equation and constant?g. How are activity coefficients calculated?

i. Limitations of Debye-Hckel Equation

ii. Relationship to hydration sphere and ionic atmosphere

E. Analyzing equilibrium reactions with activity coefficientsa. Interpreting activity coefficients from tables or Debye-Hckel Equation

b. Activity coefficients for:

i. Dilute solutions

ii.

Pure solids, liquids and gasesiii. Very low ionic strength

iv. High ionic strengthc. pH and activity

d. using ionic strength and common ions

e. successive approximationi. assume an activity coefficient to calculate ionic strength

ii. iterate calculates until values converge

F. Systematic Treatment of Equilibrium

a. Know how to deal with complex chemical equilibriab. Know how to calculate a charge balance equation

c. Know how to calculate a mass balance equationd. Know how to make assumptions to simplify calculations

i. Set activity coefficients to 1 to calculate ionic strength

ii. Set concentrations to zero for relatively low equilibrium constantsiii. Is the solution expected to be acidic or basic

iv. Check assumptions

Monoprotic Acid-Base Equilibria (Chapter 9)

Main Goals:

A. Fundamentals of Acid-Base Reactions:

a. How to calculate a pH for a strong acid or base?i. Relationship between pH, pOH and pKw

ii. Difference between high and low acid/base concentrationsb. How to calculate a pH for a weak acid or base?

i. Factors that effect pH or pKa

ii. General approach for base and acid


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iii. Term: formal concentration, fraction of dissociaton

B. Buffersa. What is a buffer?

b. How does it work?

c. Relationship between equilibrium constant and Henderson-Hasselbalch

Equationd. Calculate the pH of a buffer

i. Relationship between pH and pKa

ii. Limitations of a bufferiii. Choice of a buffer

e. How does adding a strong acid/base effect the pH of a buffer?

i. Terms: buffer capacity

Polyprotic Acid-Base Equilibria (Chapter 10)

Main Goals:

C. Fundamentals of Polyprotic Acid-Base Reactions:

a. What is a polyprotic acid/base?

i. Different forms: base, acid and intermediate.b. How does pH relate to pKa and protonation state?

i. Factors that effect pKa

c. How to determine a pH for a diprotic acid.

i. What is the assumption to simplify the calculations?ii. Calculations for acid, base and intermediate forms.

a) Relationship between pH and pKa for intermediate form

d. Buffers for diprotic acid/basei. Multiple forms of Henderson-Hasselbalch equation

a) Choice of equation based on what is known

b) Solution only has one pH

ii. Effect of strong acid/base on pHe. Know how to extend the treatment of pH and buffers to polyprotic systems

i. Relationship between pH, pKa and protonation state

ii. Know how to use fractional composition equationsiii. Term: isoionic point, isoelectric point

a) Relationship to pH and pKa

Acid-Base Titrations (Chapter 11)

Main Goals:

D. Understanding the Details of an Acid-Base Titration Curve:a. Kw=Ka

.Kb


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b. pKa= -logKa

c. pH = -log[H+]

d. Equilibrium equation for weak acid and base dissociation

i. Ka= [H+][A

-]/[HA]

ii. Formal concentration (F)

e.

Titration of a strong acid with a strong basei. Strong acid and base completely dissociatea) Titration is simply: H++ OH-H2O

ii. How does pH change as a titrant is added?a) pH = 7 at equivalence point

iii. Three regions of the titration curve

a) Before, after and at equivalence point

f. Titration of a weak acid with a strong basei. Reaction goes to completion

a) Converts weak acid to its conjugate base

ii. How does pH change as titrant is added?

a)pH is NOT =7 at equivalence pointiii. Four regions of the titration curve

a) Before titrant is added, treat as a weak acidb) Before equivalence point, treat as a buffer

1. know Henderson Hasselbach equation

c) At equivalence point, all weak acid converted to conjugatebase. Treat as a weak base.

1. pH is basic

d) After equivalence point, pH is determined by strong base

e) Account for dilution during titrationiv. Important features of a titration curve.

a) Equivalence point = maximum slope (inflection point)1. corresponds to Ve

b) At minimum slope before equivalence point:1. pH = pKaat 1/2Ve

2. Maximum buffer capacity

c) Slope change depends on pKa1. smaller pKalarger slope change

d) Slope change depends on [HA]1. Higher concentrationhigher slope change

g. Titration of a weak base with a strong acid

i. Very similar to weak acid with strong basea) Just reversed

ii. Only difference:

a) Before added titrant, treat as weak baseb) At equivalence point, treat as weak acid

1. pH is acidic

c) pH at 1/2Ve= pKaof conjugate acidh. Titration of a diprotic system

i. Similar to monoprotic system


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ii. Differences:a) Two equivalence pointsb) pH at first equivalence point determined by intermediate

form of the diprotic acid

iii. Separation of equivalence points depends on:a)

Relative difference in Kasb) Relative strengths in Kas between titrant and analyte

i. Difference between equivalence point and endpoint.

i. Endpoint: marked by physical changeii. Equivalence point: equal moles of analyte and titrant

j. Calculate equivalence volume (Ve)

i. M1V1=M2V2

ii. Inverting chemical reactionk. Methods of Identifying equivalence points

i. Visual identification of inflection point

ii. Plotting first or second derivative

a)

1

st

derivative maximab) 2nd

derivative null

iii. Interpolated x-intercept from Gran plotl. How to choose an acid-base indicator

i. Color change brackets pH at equivalence point

EDTA Titrations (Chapter 12)

Main Goals:

E. Understanding the EDTA Titration process:a. What is a complexation titration?

i. Lewis acid-base titration

ii. What is a chelating agent?

b. What is a formation constant (Kf)?i. High Kfvalues for EDTA titration

c. Important chemical features of EDTA

i. 7 different acid-base formsii. 6 different pK values

iii. The most basic form (Y4-

) primarily reacts with metal ion

iv. The fractional composition () of Y4-

is strongly pH dependent

v. EDTA binds tightly to multiple metal ionsa) Kfis modulated by pH

1. may need auxiliary complexing agents to prevent

insoluble metal hydroxide formation

2. must bind metal ion weaker than EDTA

b) Kfdecreases with increasing acidity

1. Y4-decreases with increasing acidity

d. Important features of an EDTA titration


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i. Titration needs to be buffered to treat Y4-as a constantii. Relationship between Kf and Kf

iii. Relationship between formal EDTA concentration and Y4-

iv. EDTA complex formation equilibrium constante. Calculate EDTA titration curve

i. Reaction goes to completiona) Large Kf

ii. Monitor pM = -log [M]iii. Three regions

a) Before equivalence point, metal ion concentration

decreases proportional to added EDTAb) At equivalence point, free metal ion concentration is

determined by Kf

c) After equivalence point, free metal ion concentration

determined by excess EDTAd) Account for dilution during titration

iv.

Slope of titration curve depends on Kfa) Larger Kf larger slope easier identification ofequivalence point

f. How to determine EDTA Endpoints

i. Ion-selective electrodeii. Metal-ion indicator

a) How to choose an indicator?

1. pK vs. pH of titration

2. indicator needs to be unprotonated to bind metal ion

3. lower Kfrelative to EDTA

b) change in color when it binds metal ion

Fundamentals of Electrochemistry (Chapter 14)

Main Goals:

F. Understanding Redox Reactions:a. What is a redox reaction?

b. What is reduction?

i. What is an oxidizing agent?ii. What is the cathode?

c. What is oxidation?i. What is a reducing agent?

ii. What is the anode?

d. What is electric charge (q)?

i. Coulombs (C)

ii. Faraday constant (F)iii. Relationship between charge and moles (q=nF)

iv. What is an electric current?


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a) Ampere (A)

e. What is electric potential (E)?i. Separation of charge

ii. Relationship to free energy (G=-nFE)iii. Voltage that can be generated by chemical reaction

iv. Relationship to equilibrium constant

f. Relationship between cell potential and G

i. What is a galvanic cell?ii. What an electrolytic cell?

iii. What is the sign of E and G for spontaneous and non-spontaneous reactions?

iv. What is the potential of a cell at equilibrium?

a) Potential of a cell measures how far a reaction is from

equilibrium

g. What are the components of an electrochemical cell?i. What is a half-cell reaction?

a) Keep track of moles of electronsii. What is a net reaction?

iii. How do electrons flow?

iv. What is an electrode?v. What is a salt bridge?

h. Short-hand notation for representing a cell

i. How to write the cell reactions from the short hand notation

ii. Anode to cathode (left to right)iii. Include solution concentrations (or activities)

iv. Phase boundaries & salt bridgesi. What is the standard reduction potential (Eo)?

i. What are standard conditions?

ii. How are standard reduction potentials measured?

a) Standard hydrogen electrode (S.H.E.)

iii. Reactions always written as reductionsiv. As Eoincreases:

a) More favorable the reactionb) More readily compound is reducedc) Better oxidizing agent

j. How to calculate standard cell potential (Eocell)?i.

Ecell= E+- E-ii. Determine if reaction is spontaneous

05916010 .nE

o

K

quiz 2 goals

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