Qualitative Analysis (4C):A Foundation for Lab Skills

Concept PresentationTuesday, July 13, 2010

C. Burt

Presentation OutlineIntroduction

Curriculum ExpectationsStudent Demographic

Instructional ApproachesMisconceptionsTextbook Issues

Assessment & EvaluationReferences

What is Qualitative Analysis?

Qualitative Analysis

http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA3/STILLS/FEZNSUL/FEZNSULF/64JPG48/6.JPG

http://edu.glogster.com/media/1/9/42/67/9426718.jpg

http://www.gettyimages.ca/detail/200448588-001/Riser?language=en-US&location=CAN

Curriculum ExpectationsB2.3 investigate precipitation reactions and flame tests, using

qualitative analysis instruments, equipment and techniques [PR, AI]

B2.4 conduct qualitative analysis of an unknown sample, using a flow chart and experimental procedures, including flame tests and precipitation reactions to determine the presence of metal ions [PR, AI]

B2.5 identify an unknown gas sample by observing its emission spectrum and comparing it to the spectra of known gases [PR, AI]

What does it look like?

http://gabudjr.files.wordpress.com/2009/11/flammes_colorees_petit.jpg http://staff.norman.k12.ok.us/~cyohn/index_files/ddlab_files/image001.jpg

What does it look like?

http://www.physics.umd.edu/courses/Phys401/bedaque07/discrete_spectra.jpg

Who are the Students?

SNC2DGrade 10, Academic

SNC2PGrade 10, Applied

SCH4CGrade 12, College

Why is it important?Forensics

identification of unknown materialsassociation of unknowns to potential sources

Fireworksproduction of colourful pyrotechnic displays for entertainment purposes

Food/Water Quality Analysiscontamination recognition toxicity testing

Astronomy indirect identification of atoms on celestial objects

Instructional Approaches

Course ContextMatter & Qualitative Analysis = first unit of SCH4C

review the periodic table, symbols and atomic theoriesfoundation for the remainder of the course (Shamai

and Stavy, 1986)develop good lab skills

Proposed Sequence – Lesson #11. Review physical properties of matter

2. Relate unique chemical structure to qualitative properties examine solids and solutions

3. Introduce the flame test as a qualitative technique compare solution colours to flame colours demonstrate technique for lab disclose what they need to show for evaluation

Misconceptions

1. impossible to differentiate between white powders

2. colour of solid and solution is identical or similar to that of the flame test colour

Demo / Display #1

Ions Symbol Colourchromium (II)

copper (II)Cr2+

Cu2+blue

chromium (III)copper (I)

iron (II)nickel (II)

Cr3+

Cu+

Fe2+

Ni2+

green

iron (III) Fe3+ pale yellow

cobalt (II)manganese (II)

Co2+

Mn2+pink

Textbook TablesSolution Colour

Flame ColourIon Symbol Colour

lithium Li+ red

sodium Na+ yellow

potassium K+ violet

cesium Cs+ violet

calcium Ca2+ red

strontium Sr2+ red

barium Ba2+ yellowish-green

copper Cu2+ bluish-green

boron B2+ green

lead Pb2+ bluish-whiteChemistry 11, McGraw-Hill Text

Remake the Tables!have the students make the tables

encourage good lab skillsallow them to test multiple times

Ions Symbol Colourchromium (II)

copper (II)Cr2+

Cu2+blue

chromium (III)copper (I)

iron (II)nickel (II)

Cr3+

Cu+

Fe2+

Ni2+

green

iron (III) Fe3+ pale yellow

cobalt (II)manganese (II)

Co2+

Mn2+pink

http://www.cwcompliance.com/whmis_flammable.jpg

Proposed Sequence – Lesson #21. Pre-lab preparation

2. Conduct lab students generate their own tables

3. Practice assessment students use their generated tables with unknown

samples can self-assess whether their tables were poor or helpful test household solutions

Proposed Sequence – Lesson #31. Introduce precipitate formation as a qualitative

technique demo #2

Demo #2

Proposed Sequence – Lesson #31. Introduce precipitate formation as a qualitative

technique demo #2

2. Review terms (soluble, insoluble, aqueous)

3. Demonstrate how to read solubility tables

4. Experiment with various dropper bottles and spot plates allow students time to see reactions and associate

solubility table

Textbook Table – Example #1

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Textbook Table – Example #2

http://www.professormeyer.com/images/solubility%20chart.jpg

Textbook Table – Example #3Anions

Cl-Br-

I-

S2- OH- SO42- CO3

2-

PO43-

SO32-

C2H3O2- NO3

-

HighSolubility

(aq)≥ 0.1 mol/L(at SATP)

most Group 1Group 2

NH4+

Group 1

NH4+

Sr2+

Ba2+

Tl+

most Group 1NH4

+most all

All Group 1 compounds, including acids, and all ammonium (NH4+)

compounds are assumed to have high solubility in water.

Low solubility

(s)< 0.1 mol/L (at SATP)

Ag+

Pb2+

Tl+Hg2

2+

(Hg+)Cu+

most most Ag+

Pb2+

Ca2+

Ba2+

Sr2+

Ra2+

most Ag+ noneCat

ions

Solubility Song

Evaluation1. Standard pen & paper

test (I)

2. Practical test (K / I)

3. Make a fire log which burns in a specific colour sequence. (A)

4. Identification of ions in drinking water (I)

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References1. Ministry Documents – Grade 11 and 12 Science

2. Shamai, R. and Stavy, R., Teaching an Introductory Course in Qualitative Analysis in Order to Enhance Learning General Chemistry, J. Chem. Educ., 1986, 63 (8), p 707

3. Chemistry 12 College Preparation, Nelson Text, 2004

4. Chemistry 11, McGraw-Hill Text, 2001

5. www.otfchemistry.webs.com