Topic 11: Measurement and Data Processing
11.1 Uncertainties and Error in Measurement and Results
Qualitative analysis
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Based on chemical or physical properties
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reactivity
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solubility
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melting point
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mass spectra
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etc.
Quantitative analysis
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Amount or concentration expressed as numerical values and appropriate units.
Precision
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the closeness of agreement between independent test results
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lower random error= higher precision
Accuracy
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the closeness of the agreement between results and the true
Significant Figures
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Number of figures reflecting the precision of a given measurement
Systematic errors
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Flaw in the design of the experiment or misuse of equipment
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Instrumental errors
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Example: Faulty calibration of equipment
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Experimental methodology errors
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Example: Calorimeter insulation
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Personal errors
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Example: Reading of graduated cylinder
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Affect accuracy
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improve: adopt greater care to experimental design
Random erros
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Cannot be eliminated, but reduced--> repeated measurement
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affect precision
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Example: estimating quamtity between graduations
Absolute and relative uncertainty
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Absolute: related to measurement
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Relative: related to size of measurement (%)
11.2 Graphical Techniques
Slope of a line
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tangent at a certain point
Intercept
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extrapolation
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y=ax+b
Best fit line
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Trendline
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Need R squared
Sketch
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Labelled but unscaled axis
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show proportionality
Graph
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Labelled and scaled axis
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quantitative measurement

11.3 Spectroscopic Identification of Organic Compounds
Index of hydrogen deficiency (IHD)
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used to determine number of rings or multiple bonds in a molecule
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degree of unsaturation is used to calculate the number of pi bonds and number of rings where:
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Double bond: one degree
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Triple bond: two degree
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Ring:one degree
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Aromatic ring: four degree
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OR: IHD = 0.5(2c+2-h-x+n)
Infrared spectroscopy
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Identifies various functional groups
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based on spring model
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symmetric stretch
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symmetric bend
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asymmetric stretch
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Fingerprint region should not be taken into consideration

Proton nuclear magnetic resonance (1HNMR)
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Information between different chemical environments of hydrogen atoms
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Table 27 of data booklet
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shows the relative number of hydrogen atoms present

Mass spectrometry (MS)
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Highly energetic ions, may break in smaller fragments, some of which may be ions.
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Section 28 of data booklet shows fragmentation pattern
