Chem 321 Chapter 1

Welcome to Chem 321

A key course to your future success

ANALYTICAL CHEMISTRY

COURSE OUTLINE

Instructor: Dr. X. Nancy Xu

Office: Alfriend Chemistry Building Room 201

Office Hours: MW 7:10-8:00 PM (OCNPS 200)

Right after the class

Teaching Assistant: Dr. Tao Huang and Jill Lowman

Email: [email protected]

MW 5:45 – 7:00 PM

OCNPS Room 200

Class Time & Place

MATH 102 or equivalent

CHEM 115, 116.

Pre-requisites

Textbook

Quantitative Chemical Analysis, 7th edition, D. Harris, Freeman, 2007.

Reference Book

Fundamentals of Analytical Chemistry, 7th Ed.

Skoog/West/Holler, Saunders Publishing, 1996

One copy of the book is placed in the reserved desk of the library.

About Textbook

PrefaceChapter 1-16 (Chem 321) Summary

Questions and Problems

Answers to the problems: in the reserved desk in the library

Glossary G-1… on the back of the book

Chapters heavily associated with Chem 322

Course Website• Class notes, assigned problems and announcements

are posted at http://www.odu.edu/sci/xu/chem321/chem321.htmhttp://www.odu.edu/sci/xu/chem321/chem321.htm

• Visit this site as frequently as possible, especially before and after every class

• You will need Acrobat Reader to download large documents

Honor Code

• Students registered for CHEM 321 are

expected to obey the ODU Honor Code!!!

AttendanceAttendance at class meeting is compulsory.

Regular and punctual class attendance is required of all students.

If you are absent, you will be responsible for everything covered in class including any handouts (e.g., problem sets, answers, sample tests, etc).

Absence from ExamsMissed exams may be made up only with a medical excuse (written by physician or health center), death or hospitalization in the family.

Without these reasons, one will earn a “zero”grade on that test.

No exceptions will be made. Please contact me prior to the exam if you must be absent.

HomeworkAssigned homework is mandatory.

Working on these assignments in a timely manner is the best way to learn the material and get good grades.

I may check your assignments and sample your homework on the due date even though it may not be graded.

The brief answers to assigned problems are available in the solution book, which is placed in the reserved desk in the library .

Exams

• 4 unit tests and a comprehensive final examination

Grading• Average cumulated grade = unit tests

(70%) and final exam (30%)

100-93 = A 92-90 = A-

89-87 = B+ 86-83 = B 82-80 = B-

79-77 = C+ 76-73 = C 72-70 = C-

69-67 = D+ 66-63 = D 62-60 = D-

<60 = F

Tentative Timeline

Date Chapter Topic Homework

01/08 1 Measurement 1-12, 17, 22, 28, 31, 32, 34 01/10 3 Experimental Error 3-1, 2, 5, 10, 12, 13, 15, 16, 22 01/15 Martin Luther King Holiday- No classes 01/17, 22 4 Statistics 4-A, E, F, 11, 14, 17, 20 01/24 1st Unit Test (Chapter 1, 3, 4) 01/29, 31 6 Chemical Equilibrium 6-4, 15, 16, 19, 22, 25, 30, 37, 47, 48, 5302/5, 7 7 Let the Titrations Begin 7-B, F, 7, 22, 23, 28, 36 02/12, 14, 19

8 Activities and Systematic Treatment of Equilibrium

8-A, B, C, E, F, G, 2, 4, 11, 12, 18, 20, 24, 26

02/21 9, 11 Monoprotic Acid-Base Equilibrium 9-B, D, E, 2, 5, 6, 22, 23, 27, 28, 33 02/26 6-9 Recitation and help session 02/28 2nd Unit Test (Chapter 6-9) 03/05-10 Spring Break- No classes 03/12, 14 10, 11 Polyprotic acid-Base Equilibrium 10-A, B, D, 4, 11, 17, 18, 23 03/19, 23 11 Acid-Base Titration 11-A, B, F, 3, 6, 14, 19, 23 03/26,28 12 EDTA Titration 12-C, D, 1, 2, 3, 7, 8, 24, 34 04/02 3rd Unit Test (Chapter 10-12) 04/04, 09 14 Fundamentals of Electrochemistry 14-B, C, D, 2, 10, 25 04/11,16 15 Electrodes and Potentiometry 15-4, 8, 9, 21, 26 04/18 16 Redox Titration 16-A, 1, 2, 6, 13 04/23 4th Unit Test (Chapter 14-16) 04/30 3:45-6:45 PM Comprehensive Final Examination (Chapter 1-16, except 2, 5 and 13)

Note to the class

• Welcome to Chem 321, a key course to your future success in analytical data analysis and experimental design of any chemical related problems in every scientific disciplinary including chemistry, biology, biotechnology, forensic science, food science, material science, medicine, environmental science, etc.

• Whether you aim to be a brilliant scientist, a medical doctoral, a technician or a good cook, you will find this course essential and helpful for your future career.

What are we going to do in the class ??

• We will introduce basic analytical concepts and theories and focus on data analysis and interpretation.

Six tips for success in this class• actively attending every class and take good

notes • improving your math (good math is absolutely

essential)

• completing all homework and study textbook, class notes and slides

• asking questions

• coming to Dr. Xu’s office hours

• visiting course website frequently.

Good-luck to you!!

---Dr. Nancy Xu

Chapter 1: Introduction & Measurements

What is Analytical Chemistry?

“Analytical Chemistry is what analytical chemists do.”

--- C. N. Reilley

Roles of Analytical ChemistryPlay a vital roles in all sciences, just to name of a few: chemistry, biology, biotechnology, forensic science, food science, material science, medicine, environmental science, etc.

Examples of achievement of Analytical chemistry:

Breakthrough of the century: Sequence of Human Genome, Analytical chemists-capillary electrophoresis.

Classification of AnalysisQualitative Analysis

determination of chemical identity of the species in the sample.

Quantitative Analysisdetermination of the amount of species or analytes, in numerical terms. Hence, Math is heavily involved.

In order to perform quantitative analysis, typically one needs to complete qualitative analysis.

One needs to know what it is and then select the means to determine the amount

Classification of Quantitative Methods of Analysis

Gravimetric Method: mass is measured.

Volumetric Method: volume is measured or used to determine amount of sample via concentration.

Instrumental Method: use an instrumental technique to assay the amount of sample:

Such as: Electroanalytical based upon electron-transferSpectroscopy including mass spectrometry

(***hot) (proteomic)

Steps in a Typical Quantitative Analysis

Units

SI Units

1 attoliter = 1x10-18 L

1 L = 1x1018 attoliter

1 mL = 1x10-3 L1 L = 1x103 mL

1 μL = 1x10-6 L1 L = 1x106 μL

Weight & Mass

Weight is the force of gravitational attraction between that matter and the earth.Location dependenceMass is an invariant measurement of the amount of matter.Location independenceW = mg

I. Review of Stoichiometry - please refer to your freshman chemistry text to review this concept.

A. Empirical vs molecular or structural formulas:1. Empirical formulas give information only about the simplest ratio between the different elements composing the molecule.

Example: HO, H2CO

2. Molecular formulas give information about the numbers of atoms of each element found in the molecule.

Example: H2O2, H4C2O2, C2H5OH, C2H4O2, C3H6O3, C6H12O6

3. Structural formulas give information about the structure of the molecule as well as the numbers of atoms of each element

Example: HOOH, (CH3)3COH, CH3CH2OCH2CH3,

B. The Mole (mol):

A unit which defines the number of units of a chemical species (molecules, atoms, ions, etc.) and from which we can calculate the weight of the species if we have a knowledge of the chemical formula of that species.

Avogadro Number:

6.022 x 1023 particles is one mole.

Example I-1

Calculate molecular weight (molar mass) of CH2O(Formaldehyde) and C6H12O6 (glucose)1 mole of C = 12.0 g1 mole of H = 1.0 g1 mole of O = 16.0MW of CH2O =12.0 + 2x1.0 + 16.0 =30.0 g/mole

MW of C6H12O6=6x12.0+12x1.0+6x16.0=180.0 g/mole

Example I-2

How many moles and millimoles are contained in 2.00 g of pure benzoic acid (C6H5COOH) (MW = 122.1 g/mol)

Moles of benzoic acid = mol0164.01.122

00.2MW

Weight ==

mmoles of benzoic acid = moles x1000 =16.4 mmol

Solution

Solute: a minor species in a solution

Solvent: a major species in a solution

(e.g., water is a solvent for aqueous solution)

Chemical ConcentrationsMolar Concentrations:

Molarity (M) = solute/solution (mol/L)Molality (m) = solute/solvent (mol/kg)

Percent Composition

Weight percent

Parts per million (ppm)Parts per billion (ppb)

Volume percent

MolarityMolarity

The number of moles of species (x) dissolved in 1 L of solution

Molar ConcentrationMolar Concentration

mol/L = M(L)Solution of Volume

(mole) Solute of Moles ofNumber Cx =

(g/mol) solute ofMW

(g) Solute ofWeight (mole) Solute of Moles ofNumber =

Analytical Analytical MolarityMolarity::The total number moles of a solute (regardless its chemical state) in one liter of solution

Example-I-3:117.0 g of NaCl dissolved in 1.00 L of water has an analytical concentration of _____ mol /L MW of NaCl = 58.5 g/mol

ConcentrationConcentration

mole00.25.580.117

MWW NaCl of Mole

NaCl

NaCl ===

M00.2 mole/L00.2L00.1

moles00.2(L) V

MoleC NaClNaCl ====

Example I-4:294.0 g of H2SO4 dissolved in 1.00 L of water has an analytical concentration of ____ mol/L MW of H2SO4 = 98.0 g/mol

moles00.3g/mol0.98

g0.294MWW

SOH of Mole42

42

SOH

SOH42 ===

M00.3 mole/L00.3L00.1

moles00.3(L) V

MoleC lSOH

SOH42

42====

Molality

(kg)solvent of Weight (mole) Solute of moles ofNumber Cweight =

Density:Density:

Expresses the mass of a substance per unit volume.

In SI Units: density unit --- g /mL or kg/LExample: Density of water is approximately 1.00 g/mL at 40C.

Weight = Volume x density

DensityDensity

Practice at Home

Assume density of solution in Examples I-3 and I-4 = 1 g/ml3,

what is the molality of the solution in Examples I-3 and I-4, respectively?

Percent Concentration

1.

2.

3.

%100xsolution of mass

solute of mass (w/w)percent Weigh =

%100xsolution of volume

solute of volume (v/v)percent Volume =

%100x (mL)solution of volume

(g) solute of mass

(w/v)percent umeweight/vol

=

Example I-5:What is the w/w % of an aqueous ammonia (NH3) solution at

14.3 M, with density = 0.900 g/mL (900 g/L)?

Solute : NH3

1) MW of NH3 = 17.0 (g/mol)

2) Mole of NH3 at 14.3 M in 1.00 L=14.3 (mol/L) x 1.00 L=14.3 mol

3) Weight of NH3 at14.3 M in 1.00 L = Mole of NH3 x MW of NH3= 14.3 mol x 17.0 (g/mol) = 243 g

4) Weight of 1.00 L solution = volume x density = 1.00 (L) x 900(g/L) = 900 g

27.0%x100%900

243x100%

solution of mass

solute of mass (w/w)percent Weigh ===

Example I-6:What is the molar concentration of an aqueous ammonia (NH3)

solution with density = 0.900 g/mL (900 g/L) and 27.0% (w/w)?

Solute : NH3MW of NH3 = 17.0 (g/mol)

Weight of NH3 = Mole of NH3 x MW of NH3 =CNH3VNH3 x MW of NH3

Weight of 1.00 L solution = volume x density = 1.00 (L) x 900 (g/L) = 900 g

27.0%x100%900

Wx100%

solution of mass

solute of mass (w/w)percent Weigh 3NH

===

W NH3 = CNH3VNH3 x MW of NH3 = 243 g

CNH3 = 14.3 mol/L = 14.3 M

Example I-7: What is the v/v% of ethanol in a solution prepared by mixing 5.00 mLof ethanol with enough water to give 1.00 L of solution?

Solute: ethanol

1) Volume of solute (ethanol) = 5.00 mL = 5.00 x10-3 L2) Volume of solution = 1.00 L

3)

%500.0%100L00.1

L1000.5

%100xsolution of volume

solute of volume (v/v)percent Volume

3

==

=

−

xx

pph10x solution of mass

solute of mass (w/w) C 2pph =

ppt10x solution of mass

solute of mass (w/w) C 3ppt =

parts per hundred (pph) & parts per thousand (ppt)

ppm10x solution of mass

solute of mass (w/w) C 6ppm =

ppb10x solution of mass

solute of mass (w/w) C 9ppb =

parts per million (ppm) & parts per billion (ppb)

ppt10x solution of mass

solute of mass (w/w) C 12ppt =

parts per trillion (ppt)

Stoichiometric Calculations

II. Stoichiometric Calculations:

stoichiometric calculations are based on the combining ratios of reactants which result in specific products .

They are expressed in terms of moles.

when you are given the mass of a reactant or product, you should first convert the mass to moles to determine the amount of reactant that will be consumed or product that will be produced for a given reaction.

If the final answer is to be given in a mass unit, then the moles must be converted to grams.

Example I-8(a)What mass of AgNO3 (MW= 169.9 g/mol) is needed toConvert 2.33 g of Na2CO3 (MW=106.0 g/mol) to Ag2CO3 ?

2 mol1 mol

0.10633.2

9.169W

3AgNO

9.169W

0.10633.2

21

3AgNO

= 0.10633.22

9.169W

1 3AgNO xx =

g47.79.1690.106

33.22W3AgNO == xx

Na2CO3 (aq) + 2AgNO3 (aq) Ag2CO3(s) ↓+ 2 NaNO3 (aq)

Example I-9

1 mol1 mol

0.10633.2

7.275W

32COAg

7.275W

0.10633.2

11

32COAg

= 0.10633.21

7.275W

1 32COAg xx =

g06.67.2750.106

33.21W32COAg == xx

Na2CO3 (aq) + 2AgNO3 (aq) Ag2CO3(s) ↓+ 2 NaNO3 (aq)

(b) What mass of Ag2CO3 (MW= 275.7 g/mol) will be

formed?

Preparation of Solution

Solute

Solvent

Total Solution

Example I-10:To prepare a solution with 0.500 M of Cl- from BaCl2 • 2H2O. How much of the BaCl2 • 2H2O must be used to prepare 1.00 liter of solution? Assume BaCl2 completely dissociates:BaCl2 -----> Ba+2 + 2 Cl-1 mole 2 molex mole 0.500 (mol/L) x 1.00 (L)

X mole = Mole of BaCl2 (mole) = (0.500/2) = 0.250 (mole)

MW of BaCl2 • 2H2O = 244.2 g/mol

W of BaCl2 • 2H2O = Mole of BaCl2 (mole) x MW of BaCl2 • 2H2O = 0.250 mol x 244.2 g/mol= 61.1 g

0.500x1.00mole

VCmole

molemole

21 2

--

2

-

2 BaCl

ClCl

BaCl

Cl

BaCl ===

Dilution Dilution the number of moles are the same in dilute and concentrated solutions!

moles = CconcentratedVconcentrated = CdiluteVdilute

Units: V: either in L and mLC: M (mol/L) or mM (mmol/L)

Be sure to match units for both dilute and concentrated solutions

Volumetric CalculationsVolumetric Calculations

Example I-11:

An aliquot of a HCL solution (1.00 M) has been diluted with three equal aliquots of H2O to prepare 1:4 aq HCl. In other words, the HCl has been diluted fourfold. The dilute concentration of the HCl is:

M)(25.041x00.1

V xV(M)C

(M)Cdilute HCl,

edconcentrat HCl,edconcentrat HCl,dilute HCl,

==

=


Example I-12:

How many L of a 50 mol /L solution are How many L of a 50 mol /L solution are required to make 200 required to make 200 mL mL of a 1 mol Lof a 1 mol L--11

solution?solution?

50 (mol /L) * Vconc. = 1 (mol/L) * 0.200 L

Vconc. (L) = (1 M * 0.200 L) / 50 M

= 0.004 (L)


Summary

Course Overview:

Classification of Analysis :

Units:

Molecular Weight:

Mole:

Concentrations:

Stoichiometric Calculations:

Preparation of Solution:

Homework

Chapter-1: 1-12, 17, 22, 28, 31, 32, 34

Practice with all examples that we discussed in the classand related examples in textbook!!

Before working on Homework,

Any Questions???

The End!

Chem 321 Chapter 1

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