Using Basic Lab Techniques To Identify Inorganic Contaminant

Using Basic Lab Techniques To Identify Inorganiccontaminantsmichael Po

Using Basic Lab Techniques to Identify Inorganic Contaminants Michael Pool CHM2045L.912 Yiming Li March 9th 2017 Introduction Determining a chemical substance can be extremely important when given an unknown. Chemicals have many qualities that are unique, often times only sharing that quality with a handful of other substances. Identifying these qualities through reactions allows us to narrow down what our unknown could possibly be. Reactivity is simply a chemicals reaction to other chemicals or extremes. Using reactivity we can find out more about the substance and make decisions based on what is in front of us.

For example, many chemicals have obvious reactions to open flame. Depending on a chemicals reaction to the extreme heat of a flame, we can often times narrow our unknown to a specific group of chemicals. According to EAG Labs, there are a few basic questions we can run through before we begin any tests on our chemical to possibly assist in identifying our unknown. Is there expected to be a large amount of contaminate? What are the physical attributes of the substance? Any color, odor, or residues? Once we made these inferences we began testing our substance, narrowing down the possibilities and continued to test within our new parameters. Following the tests in this lab should provide the name of the chemical that begins as an unknown, within a reasonable margin of error.

Methods

In this experiment we were given an unknown inorganic contaminant and told to identify it. Using qualitative and quantitative tests, we found the identity of our unknown.

Part 1

In the first week of the experiment we started with qualitative tests; flame, solubility, conductivity, and pH. To begin with, we did the flame test. We took a small sample of our given unknown and exposed it to an open flame. We recorded this result and repeated the test two additional times, receiving the same result. Our next test was conductivity, we placed the instrument in a beaker with a solution containing 1% of our unknown and remaining water.

Our third test was pH, we placed the solution in a beaker with some basic pH indicator strips, matching their color to the chart. Our final test of week one was solubility, which we did last because after this test our solution is contaminated and not useful for further tests. We tested the solubility of our unknown with Barium Nitrate, Sodium Hydroxide, and Silver Nitrate. We added each substance in separate sections of a solubility tray and recorded the results. We completed three trials of each to ensure accuracy.

Part 2

In the second week, with the data from week one, we performed quantitative tests based on our assumptions about the unknown. The options were gravimetric or volumetric analysis. Since our unknown appeared to be soluble and basic, we chose volumetric titration. We set up a burette with an appropriate titrant, added an indicator, and titrated the solution, recording pH changes as we added the titrant until reaching the endpoint. The volume used at the titration point was recorded for analysis.

Prior to conducting the titration, safety procedures were strictly followed. We wore personal protective equipment including goggles, gloves, and lab coats. We handled chemicals with caution, especially those requiring hood use, and prepared for spills and accidents accordingly.

Results

Qualitative Tests

Week 1 results are summarized in the following tables:

Solubility Testing Results

The consistent yellow flame indicated the presence of sodium or lithium, with the test favoring sodium compounds. The solubility in NaOH and the conductivity readings supported the hypothesis that the unknown was likely sodium hydroxide. The pH reading of 10 was slightly lower than the typical pH of pure sodium hydroxide (~13), which could be due to contamination or impurities in the sample.

Quantitative Titration Results

The titration curve showed a gradual pH increase until a sharp rise at the equivalence point. The volume of titrant used to reach the endpoint was recorded, indicating a high concentration of the unknown solution, consistent with a strong base like sodium hydroxide.

Discussion

The combined qualitative and quantitative data point towards the unknown being sodium hydroxide (NaOH). The yellow flame test aligns with sodium’s characteristic emission, a well-documented phenomenon (Avery & Madden, 2004). Conductivity measurements confirmed the presence of ions capable of conducting electricity, consistent with ionic compounds like NaOH. The solubility test, which showed complete dissolution in sodium hydroxide, further supported this conclusion.

While the pH value was lower than expected, measurement error or sample contamination could explain this discrepancy. Pure sodium hydroxide solutions typically demonstrate a pH near 13 (Pretsch et al., 2009). The volumetric titration reinforced the hypothesis, providing quantitative data consistent with a strong base's typical titration profile. Overall, the evidence strongly suggests that our unknown is sodium hydroxide, a common inorganic base used in laboratories and industrial processes.

This experiment highlights the importance of combining various qualitative and quantitative techniques for chemical identification. The flame test and solubility tests are quick, inexpensive, and illustrative, while titration provides precise quantitative data. Such methods are valuable in analytical chemistry applications, including environmental testing of pollutants or clinical diagnostics (Skoog et al., 2017).

Conclusion

In conclusion, through systematic application of basic lab techniques—flame test, solubility analysis, conductivity measurement, pH testing, and titration—we successfully identified the unknown inorganic contaminant as sodium hydroxide. This approach demonstrates how careful qualitative observation and quantitative analysis complement each other in chemical identification. Such methodologies are essential tools in analytical chemistry, environmental science, and quality control processes, ensuring accurate substance identification even in complex samples.

References

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