Monique A. Gray
Experiment 4
Quantitative Analysis
Experiment 4: Comparison of Two Chloride Determinations
Introduction
This experiment embodies the understanding of volumetric analysis of a compound and a gravimetric analysis of a
compound. Thus, in this experiment one will analyze the amount of a compound by engaging to the “wet”
chemical techniques in analysis. The first technique in the volumetric analysis technique and the next technique is
the gravimetric technique. Finally, after all the proper data and collected for both procedures/experiments a
statistical analysis will be done to compare the effectiveness of each technique.
Reaction
𝐴𝑔𝑁𝑂3 + 𝐶𝑙 − → 𝐴𝑔𝐶𝑙(𝑠) + 𝑁𝑂3−
𝐴𝑔𝐶𝑙(𝑠) → 𝐴𝑔+ + 𝐶𝑙 −
Procedure
Volumetric Chloride Determination
-
Weight out about 4.0000g of AgNO3 and dissolved in 100mL of distilled water. Once dissolved completely,
transfer solution to a 200mL volumetric flask and dilute and invert to mix properly.
Weight out about 0.1g of an unknown chloride sample and empty contents into a 125mL flask. Do this
two additional times. To each individual flask add 50mL of distilled water.
Add 0.03g of dextrin and 5 drops of dichlorofluorescein indicator.
Titrate each sample (made in the last two steps) with AgNO 3.
Calculate the percent chloride is the each sample that was titrated.
Gravimetric Chloride Determination
-
Prepare three Gooch Crucibles by cleaning with an acid solution (0.1M HNO 3) followed by a basic solution
(0.1M NH3), then finally rinse each crucible was distilled water.
Dry crucibles in the oven at 120 degrees Celsius and add a glass fiber filter to each one. Then weight each
crucible. (Make sure mass is consistent and handle crucible with tongues NOT hands.)
Weight out 0.2g of unknown chloride sample three times.
Dissolve each sample with 150mL distilled water in a 400mL beaker. Then add 1mL of 6M HNO3.
Add AgNO3 to completely precipitate the solution and the heat until supernate is not longer cloudy.
Assemble a gooch crucible filtration apparatus.
Filter each sample and wash with warm 0.1M HNO3.
Allow crucibles to dry for at least 2 hours in a 120 degree Celsius oven.
Take the final weight.
Monique A. Gray
Experiment 4
Data/Calculations
Volumetric Determination
Mass of AgNO3 = 4.005g
Volumetric Titration
Mass of Unknown
0.1014g
0.1017g
0.1009g
Unknown Sample #
1
2
3
mL AgNO3 titrated
13.80mL
13.86mL
14.90mL
Calculate the grams of Chloride Ion in Sample: (using sample one data)
13.80𝑚𝐿 𝑜𝑓 𝐴𝑔𝑁𝑂3 4.0058𝑔 1 𝑚𝑜𝑙 𝐴𝑔𝑁𝑂3
1 𝑚𝑜𝑙 𝐶𝑙 − 35.435𝑔 𝐶𝑙 −
= 0.0576𝑔𝐶𝑙 −
1
200𝑚𝐿 169.86𝑔𝐴𝑔𝑁𝑂3 1𝑚𝑜𝑙 𝐴𝑔𝑁𝑂3 1 𝑚𝑜𝑙 𝐶𝑙 −
Percent Chloride Ion in Sample (using sample one data)
0.0576𝑔 𝐶𝑙 −
= 0.5680 𝑥 100 = 56.8%
0.1014 𝑔
Gravimetric Determination
Mass of Unknown of Chloride Sample
1.
2.
3.
0.2043g unknown
0.2016g unknown
0.2085g unknown
Mass of Gooch Crucibles After 1hr of Drying (with glass fiber)
1.
2.
3.
23.2381g
22.5110g
22.6843g
Mass After 2hrs of Drying (with glass fiber)
1.
2.
3.
23.7116g
22.9827g
23.1722g
Mass of Chloride Product (after 2hr drying)
1.
2.
3.
0.4700g
0.4719g
0.4680g
Monique A. Gray
Experiment 4
Amount of Silver Nitrate Needed to Precipitate the Cl- ion
0.2016𝑔 𝐴𝑔𝑁𝑂3 0.5851 1 𝑚𝑜𝑙 𝐶𝑙 − 1 𝑚𝑜𝑙 𝐴𝑔𝑁𝐴𝑔𝑁𝑂𝑂3
169.86𝑔
200𝑚𝐿
= 28.23𝑚𝐿
1
1
35.435𝑔
1 𝐶𝑙 −
1 𝑚𝑜𝑙 𝐴𝑔𝑁𝑂3 4.0058𝑔 𝐴𝑔𝑁𝑂3
Mass of Chloride in sample
0.4719 1 𝑚𝑜𝑙 𝐴𝑔𝐶𝑙 1 𝑚𝑜𝑙 𝐶𝑙 − 35.453𝑔
= 0.1167𝑔 𝐶𝑙 −
1
143.32𝑔 1 𝑚𝑜𝑙 𝐴𝑔𝐶𝑙 1 𝑚𝑜𝑙 𝐶𝑙 −
Percent Chloride in Sample
0.1167𝑔 𝐶𝑙 −
= 0.5789 𝑥 100 = 57.89%
0.2016𝑔
Volumetric Percent Chloride
1.
2.
3.
56.80%
56.93%
61.70%
Gravimetric Percent Chloride
1.
2.
3.
56.93%
57.895
55.54%
Difference
1.
2.
3.
0.13
1.02
6.16
Mean of difference: 2.4367
Standard Deviation: 10.59535
Tcalc; 0.2698
Calculation for Standard deviation:
𝑠=
√∑(𝑑𝑖 − 𝑑)2
𝑛−1
Calculation for tcalc
Tcalc =
|𝑑|
𝑠
√𝑛
B. Given that t- table at a 95% confidence interval was 2.78, since t-calc was less than t-table then there is no
significant difference between the two types of ‘wet’ chemical analysis. Thus, whether chloride is analysis using the
volumetric or gravimetric technique, both techniques are proven to given similar answers.
Monique A. Gray
Experiment 4
C. The titration could be done in a manner in which droplet intervals could be done and this will lead to be better
endpoint a more accurate endpoint. The same with measuring out the mass of a sample, trying to get it closer to a
particular number or trying to get each sample’s mass within a certain range of each-other. This could produce
more accurate and consistent results. For example, if told to measure out 4g try to get exactly 4g or try to get each
measurement that was measured within possibly 0.003g within the previous measurement.
Also, when measuring out particular volumes of liquid try to choose the most appropriate glassware to measure
the liquid in. If doing so, this could significantly enhance results and possibly the yield of the reaction. Another
change or tip would be to make sure all rounding and measuring is kept consistent.
Math is a big part of mostly all experiments so checking the math and maybe recalculating someone isn’t such as
bad idea. This could possible enhance your results.
Developing a better technique to handle crucibles could drastically enhance results because weighting by
difference was one of the big measurements in this experiment and if you’re handling crucibles wrong this could
cause the mass to be a little off and in experiment where accuracy and precision matter, it’s a big error. Properly
washing crucibles could also be improved. Maybe washing them an extra time wouldn’t hurt. When drying the
crucibles an important factor is making sure that all measurement are reproducible or within 0.003g of the
previous measurement. Sticking to this technique could greatly influence your overall yield especially when you
have to weigh by difference.
Finally when filtrating the sample, you could perform an extra wash to help purify the sample even more and to
help lower the amount of impurities in the sample. A better transfer technique could also be incorporated into the
experiment, such as, using the washing solution to gather the left over sample from the bear or flask when
transferring the sample.