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Introduction toQuality Control I
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Analytical Chemistry
Qualitative Analysis Quantitative Analysis
deals with theidentification ofelements, ions orcompounds
present in asample
performed by selectivechemical reactions orwith the use
ofinstrumentation
deals with thedetermination of howmuch of one or
moreconstituents is present
a history of the samplecomposition will oftenbe known or
performeda qualitative test priorto the performing themore
difficultquantitative analysis
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Concentration
amount of analyte present in a knownamount of sample
relative amount of analyte per unitvolume or unit mass of
sample
applicable to liquid samples , gas-phasesamples and solid-phase
samples
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Concentration Units
Amount of Analyte Amount of Sample Concentration Unit
mole liter Molarity(M)
equivalent liter Normality(N)
weight weight Percent(%)
(weight/weight basis)
volume volume Percent(%)
(volume/volume basis)
weight(g)
volume(mL)
Percent(%)
(weight/volume basis)
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Concentration Units
Amount of Analyte Amount of Sample Concentration Unit
weight weight Parts per million(ppm)
(weight/weight basis)volume volume Parts per million
(ppm)(volume/volume basis)
weight(mg)
volume(L)
Parts per million(ppm)
(weight/volume basis)
amount of substance that reacts exactlywith 1-mL of standard
solution
used for equivalent weight calculations
Titer
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Significant Figures
Exercise 1
the number of digitsnecessary to expressthe results of
ameasurement
consistent with themeasured precision
List the proper number ofsignificant figures in thefollowing
numbers and indicatewhich zeroes are significant.
0.216
90.7800.0
0.0670
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Rounding Off
Exercise 2
If the digit following thelast significant figure isgreater than
5, thenumber is rounded up tothe next higher digit.
If it is less than 5, thenumber is rounded to thepresent value
of the lastsignificant figure.
If the last digit is a 5, thenumber is rounded off to
the nearest even digit.
Round off the followingmeasurements to two (2)significant
figures.
9.47
9.43
8.658.75
8.55
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Assignment No. 1
1. A solution is prepared by dissolving 1.26-gAgNO 3 in a 250-mL
volumetric flask and
diluting to volume.a. Calculate the normality of the silver
nitrate solution.
b. How many milliequivalents AgNO 3 weredissolved?
Molar masses :Ag = 107.870 N = 14.0067 O = 15.9994
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Assignment No. 1
2. How many grams Na 2 SO 4 should beweighed out to prepare
500-mL of a 0.100-
M solution?Molar masses :
Na = 22.9898 S = 32.066 O = 15.9994
3. A 1.267-g sample of limestone wasanalyzed and found to
contain 0.3684-g ofiron. What is the concentration of iron inthe
sample?
Molar mass : Fe = 55.845
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