Qualitative Analysis (4C): A Foundation for Lab Skills
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Transcript of Qualitative Analysis (4C): A Foundation for Lab Skills
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Qualitative Analysis (4C):A Foundation for Lab Skills
Concept PresentationTuesday, July 13, 2010
C. Burt
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Presentation OutlineIntroduction
Curriculum ExpectationsStudent Demographic
Instructional ApproachesMisconceptionsTextbook Issues
Assessment & EvaluationReferences
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What is Qualitative Analysis?
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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
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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]
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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
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What does it look like?
http://www.physics.umd.edu/courses/Phys401/bedaque07/discrete_spectra.jpg
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Who are the Students?
SNC2DGrade 10, Academic
SNC2PGrade 10, Applied
SCH4CGrade 12, College
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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
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Instructional Approaches
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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
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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
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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
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Demo / Display #1
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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
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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
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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
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Proposed Sequence – Lesson #31. Introduce precipitate formation as a qualitative
technique demo #2
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Demo #2
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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
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Textbook Table – Example #1
http://castlelearning.com/review/reference/chem%20table%20f.gif
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Textbook Table – Example #2
http://www.professormeyer.com/images/solubility%20chart.jpg
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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
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Solubility Song
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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