analitical chemistry i

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Anal. Chem. by Prof. Myeong Hee Moon

Subject Title

Analytical Chemistry I

3hrs / weekProf. Name

Myeong Hee Moon

2123 - 5634

LectureInfo.

Text: Quantitative Chemical Analysis 8th ed. Harris. Must Use English Version TextbookReference: Analytical Chemistry (Christian) 7th

Fundamentals of Analytical Chemistry (Skoog) 8th

Lecture note can be obtained from homepage http://chem.yonsei.ac.kr/~mhmoon

Evaluation

1st exam: 25%2nd exam: 25%Final: 25% Attendance(including Quiz) 25 %

Total 100 %

Syllabus

Analytical Chemistry - I

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Week Days CONTENTS Remark

1 3. 4∼3.8IntroductionThe Analytical Process/chemical measurements

2 3.11∼3.15 Experimental Error/Statistics

3 3.18∼3.22 Statistics/Quality Assurance & Calibration

4 3.25∼3.29 Quality Assurance & Calibration

5 4.1∼4.5 Chemical Equilibrium 04.02: 1st exam

6 4.8∼4.12 Activity & Systematic treatment of Equilibrium

7 4.15∼4.19 Monoprotic Acid-Base Equilibria

8 4.22∼4.26 Midterm

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9 4.29∼5.3 Polyprotic Acid-base Equiilibria

10 5.6∼5.10 Acid-base Titrations05.7

2nd exam

11 5.13∼5.17 EDTA Titrations

12 5.20∼5.24 Advcanced Topics in Equilibrium

13 5.27∼5.31 Fundamentals of Electrochemistry

14 6.3∼6.7 Electrodes and Potentiometry

15 6.10∼6.14 Electrodes and Potentiometry

16 6.17∼6.21 Final Exam 06.11

Syllabus

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Ch 0. Fundamentals in Analytical Chemistry

Topics : Stages in Chemical AnalysisConcentrationsStoichiometric CalculationsTitrations

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Chemistry, BiologyMedicine (hospital), Geology (geological survey)Oceanography, Material ScienceForensic Science, ArcheologyFarming, Food ScienceEnvironmental Science, etc

(Government regulations on pollution)

Analytical Chemistry Applied to:

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ANALYZE ?What is it (chemical elements) ? How much is present ?

Development of New Products ?

– want to know composition of mixturesor giving possibility of impurities

Qualitative analysisQuantitative analysis

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0-2. analytical Chemist’s Job

analyte : the species being measured in a chemical analysis

(chemical substance)

* Stages in chemical analysis

Decide First Level of Results needed.• Level of accuracy• Economical Aspect

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How much caffeine is in a chocolate bar ?

1. Sampling

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Sample preparation

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1. Formulating the question2. Selecting analytical procedure: literature survey3. Sampling4. Sample Preparation

: converting sample into a form suitable for chemical analysis- drying, sample weighing, mixing

3. Chemical Analysis4. Calibration Curves5. Interpreting the Results6. Draw conclusions

Steps in chemical analysis

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Ch 1. Chemical Measurements

1-1 SI Units (Systeme International d'Unites)

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Conversion between Units

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1-2. Chemical Concentrations

1) Molarity (M)# of moles per a liter of solution

(1 mole = g/fw)1 Liter=103cm3 = 1000cc

molecular weight - for molesformula weight - for electrolytes

(since no molecule exists in electrolyte sol.)

2) Molality (m)# of moles per a kg of solvent. temp. independent

L

molesMolarity

solute of

)(

moles of #

solventkgm

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3) Percent Composition

100mixtures total of

solute of mass(%)

masswt

100solution total of

solute of volume(%)

volumevol

4) ppm & ppb

610sample of mass

tsubstituen of mass ppm

910sample of mass

tsubstituen of mass ppb

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1-3. Preparing Solutions

Dilution Mconc Vconc = Mdil Vdil

ex) A solution of ammonia in water is called "ammonium hydroxide" because of the equilibrium : NH3 + H2O NH4

+ + OH-

The density of concentrated ammonium hydroxide, which contains 28.0 wt% NH3, is 0.899 g/mL. What volume of this reagent should be diluted to make 500 mL of 0.250 M NH3 ? (Ans: 8.45mL)

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1-4. solutions & Stoichiometry

1) Volumetric calculationa A + b B products mol A = mol Bb

a

ex) In acid solution, potassium permanganate reacts with H2O2 to form Mn2+: 5H2O2 + 2 MnO4

- + 6 H+ 5O2 + 2Mn2+ + 8 H2OIn neutral solution, it reacts with MnSO4 to form MnO2:

3Mn2+ + 2 MnO4- + 4 OH- 5 MnO2 + 2 H2O

Calculate the number of milliliters of 0.100 M KMnO4 that will react with 50.0 mL of 0.200 M H2O2 and 50.0 ml of 0.200 M MnSO4.

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2) gravimetric calculation

Cl2 2 AgCl (s) mol cl2 = 2

1mol AgCl

2clg

Gravimetric factor

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Additional Exercise in Stoichiometric Calculations

1. A 0.2638-g soda ash sample is analyzed by titrating the sodium carbonate with the standard 0.1288 M hydrochloric acid solution, requiring 38.27 mL. Calculate the percent sodium carbonate in the sample.

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2. A 0.200-g sample of pyrolusite is analyzed for manganese content as follows. Add 50.0 mL of a 0.100 M solution of ferrous ammonium sulfate to reduce the MnO2 to Mn2+. After reduction is complete, the excess ferrous ion is titrated in acid solution with 0.0200 M KMnO4, requiring 15.0 mL. Calculate the percent manganese in the sample as Mn3O4 (only part or none of the manganese may exist in this form, but we can make calculations on the assumption that it does). (Ans: 66.7%)

2 Fe2+ + MnO2 + 4 H+ 2 Fe3+ + Mn2+ + 2 H2O 5 Fe2+ + MnO4

- + 8 H+ 5 Fe3+ + Mn2+ + 4 H2O

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: Addition of titrant to analyte for calculation of conc.

Calculate conc. of analyte from how much it is consumed.

titration acid-baseredoxprecipitationSpectrophotometric biochemistry

1.5 Titrations

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Calculation of analyte conc. from how much titrant is consumed.

By HOW to DETECT ?

1. detecting sudden change in V or I2. color change (indicator)3. change in Absorbance

* Equivalence Point : ideal, stoichiometric.: occurs when the quantity of titrant added is the exact amount

necessary for stoichiometric rxn with analyte.

* End Point : actually observable point.Sudden change in color or voltage.

1.5 Titrations

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In case of titration,conc. of titrant should be known first. Is it accurate ?Use primary standard.

99.9 % or better in purity.Stable when dried by heating or vacuum

* In case of titrant which is not primary std.Use standardizationtitrate a proper primary std with the titrant. Then calculate the conc. of titrant.

1.5 Titrations

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1-6. Titration Calculations

key step : molestitrant = molesanalyte

ex) standardization of titrant - analysis of unknown

- Determination of Ca content in Urine1. Ca+2 + C2O4

2- Ca(C2O4)H2O (s) oxalate2. precipitate in ice-cold water and wash

(to remove free oxalate) then redissolve in acid3. heat to 600C, and titrate with standardized KMnO4

until purple end.

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Q1: standardization ?Suppose 0.3562 g Na2C2O4 (fw=134.00) in 250.0 mL flask.

Calculate molarity of KMnO4when 10.0 mL of the sol. consumes 48.36 mL of KMnO4.5 C2O4

-2 + 2 MnO4- + 16 H+ 10 CO2 + 2 Mn+2 + 8 H2O

1-6. Titration Calculations

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Q2: Analysis of unknown.Suppose Ca in 5.00 mL urine is precipitated and it

requires 16.17mL of std. MnO4- solution.

[Ca+] in urine ???

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Homework

In the Textbook: 1-19, 20, 30, 31, 34, 42, 45

analitical chemistry i

Documents

myeong hee moon

analytical chemistry

chemical analysis

acid solution

1st exam

sample preparation

titration calculations

analysis