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Experiment 5: Identification of an Unknown Ionic Compound

Chemistry 277 Anna Wetterer, Lindsey Roth, William Gleason

Anna Wetterer

on 9 October 2012

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Transcript of Experiment 5: Identification of an Unknown Ionic Compound

Calcium Nitrate Ca(NO3)2 typically is obtained through chemical reaction of Limestone found in caves and caverns Identification of an Unknown
Ionic Compound Experiment 5 Unknown 8: Odor Test: No Odor
Looks like White Crystals
pH test = 4
Soluble in water Identification of the Anion in the Unknown Identification of the Cation in the Unknown Flame Test Synthesis of the Compound Chemical Equation: Confirmation After the synthesis to obtain
Calcium Nitrate we performed
the same cation and anion
test to insure our results Nitrate Anion test We had difficulty with this test, We had to perform this test 4 times in order for our Positive control to show positive. 1 mL test solution
1 mL Positive control
1 mL negative control
3 mL concentrated Sulfuric acid
2 mL nitrate test reagent
look for the ring Positive Control Positive
Negative Control Negative
Unknown Positive! Results: Carbonate Anion Test Method: 1 mL test solution
1 mL positive control
1 mL negative control
add 6M HCL drop by drop
there will be bubbles if the test is positive Positive control was positive
Negative control was negative
Our sample did not bubble Results Therefore we did not have Carbonate anion in our unknown solution! Pictures!!! Chemists at Work: Therefore our unknown
has Nitrate as the anion Information on Solubility, reaction types, and methods Flame Test Cobalt glass - Blue
H2O - Nothing
Na - Orange
NH4 - Nothing
Ca - Red
Mg - Nothing
K - Purple Our unknown was red Therefore our cation was Calcium Reagents needed: Natural Occurences Contextual Info & Application Definition:
The property of a solute of any form (solid, liquid, gas) to dissolve into a solvent, which can also be either solid liquid or gaseous Solubility It was red
therefore calcium was was the cation Cation Test Dissolve Limestone in Nitric Acid to yield Calcium Nitrate Synthetic Availability Always soluble ions include but aren't restricted to:
All alkaline metal ions Picture: Some ions are almost never soluble in water unless paired with an ion that always is soluble in water. Examples include:
Sulfate Industrial Applications Acetate Anion Test 2 mL test solution
2 mL positive control
2 mL negative control
1 mL alcohol
Heat in water bath CaCO3 + 2HNO3 -> Ca(NO3)2 + H2CO3 If it smells like bananas it's positive The positive control, negative control, and the unknown all smelled like bananas

Thus we determined that we will need to identify our unknown using the other tests. Results Explosives
Pyrotechnics (the study of contained explosions) Corrosion inhibitor in diesel fuel
Waste water treatment Positive control was positive
Negative control negative
Unknown was also positive* Results 1 mL test solution
1 mL positive control
1 mL negative control
1 mL 6M HNO3
1 mL 0.1M AgNO Chloride Anion Test Reaction Types Medicine and Pharmacological Applications Metathesis reaction (Double Displacement) -Can cause irritation when in contact with skin or eyes. Recommended to wash off immediately.

-If indigestion can cause nausea, vomiting and diarrhea

-Chronic exposure has not been determined. AB+CD---> AD+BC This reaction generally includes two reactants that yield a solid precipitate and a different aqueous compound in solution. The formation of a white precipitate is evidence for the presence of chloride anion Toxicity and Environmental Hazard * We, like other groups in the class, got a false positive on this test Calcium Nitrate decomposes into NO, CaO and O2. NO and CaO are toxic gases Chloride Anion Test Challenges met with Understanding CaCO3 (aq) + 2 HNO3 (aq) → During the Chloride Anion Test, there was difficulty in identifying if there was an unknown substance for Chloride turned out positive for both the Positive Test, Negative Test, and Unknown Compound. This would be a systematic Error Ca(NO3)2 (s) + CO2 (g) + H2O(l) 1M solutions needed:
6M acids and bases needed:
HNO3 Movement of Compounds Calculations: Some of the substance could have been lost through transferal of containers. This would be a random Error. Classify unknown compound based on physical characteristics of said compound. Methods Determine cation present in compound based upon a flame test. Sulfate Anion Test Run anion tests to determine present anion (carbonate, sulfate, nitrate, acetate, chloride). 1 mL Test Solution
1 mL Positive Control
1 mL Negative Control
1 mL 6 M H2SO4
1 mL 0.1 M BaCl2 Anion Tests: There was a very obvious brown line showing that it turned out positive which is what we wanted and expected Nitrate Anion Test We did not see any bubbles therefore carbonate was not present Carbonate Anion Test The chloride anion test worked better this time and confirmed our substance was a Nitrate and not a Chloride Chloride Anion Test We completed the 5 anion tests again to confirm it was Nitrate Presence of the white precipitate indicates the Sulfate Anion. Results Positive control was positive
Negative control was negative
Unknown Substance was negative Acetate Anion Test All of them once again all smelled kind of the same, so we will have to rely on the other test Therefore our anion was not Sulfate Sources Sulfate Anion Test There was no precipitate therefore there was no sulfate present Obtain 2.3 mL of 6M HNO3 and place it in a test tube
with another test tube, obtain 0.85 g of CaCO3
obtain a 100 mL beaker and pour 6M HNO3 and CaCO3
a solid precipitation of Ca(NO3)2 should form as well as liquid H2O and gaseous CO2
Heat until water disolves leaving the solid Ca(NO3)2
Synthesis Continued Results http://toxnet.nlm.nih.gov/cgi-bin/sis/search/f?./temp/~8ubX65:1 2.23. Calcium Nitrate
[CAS: 10124-37-5]. Ca(NO3)2•4H2O, white solid, solubility 660 g/100 g H2O at 30°C, formed by reaction of calcium carbonate or hydroxide and HNO3.
Hluchan, S. E. 2005. Calcium. Van Nostrand's Encyclopedia of Chemistry.
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