What is in Our Dirt?

We determined a sample of ore contains Barium and Iron by following an analysis plan to separate unique metals from each other by combining cations and anions. Using properties we found about the cations during the first week of the lab, we mixed anions with the sample of ore until we formed precipitates of known cations.

Qualitative Analysis

Author: John McGowan

Lab Partners: Chelsea Brown, Peter Gardner

Instructor: Joel Jorolan

Chem 151, Section 54

Date Work Performed: October 20th, 2009

Date Work Submitted: November 3rd, 2009

Abstract

We determined a sample of ore contains Barium and Iron by following an analysis plan to separate unique metals from each other by combining cations and anions. Using properties we found about the cations during the first week of the lab, we mixed anions with the sample of ore until we formed precipitates of known cations.

Introduction

The objective of the experiment was to find the chemical makeup of a sample of ore to determine if a location would be financially profitable to mine. To determine this, we first determined what cations would form a precipitate with certain anions so that it would be possible to separate the anions based on this knowledge. Using a series of well plates, we mixed the cations with the anions in a controlled manner to determine which cations would form precipitates with which anions.

Once we determined this we formed a new series of well plates to test the cation spot tests. With the spot test we determined the results of certain tests to determine how certain cations will prove to be what they are expected to be. With the results of the known solutions we were able to create a flow chart to determine how the cations in the ore sample would react if they were present.

We began week two of the experiment by testing our analysis scheme and found the results to be inconclusive for Aluminum and Barium. While testing our analysis scheme we were warming our ore sample so we could perform tests on it later.

Once the ore had dissolved we used the centrifuge to remove any solid still in the mixture and decanted the liquid into a separate test tube and began following our analysis scheme. We used the centrifuge in every case we wanted to remove a precipitate from the solution so that the solids would collect at the bottom of the centrifuge tube and the supernatant could be decanted from from the tube.

Results

Table 1: Precipitates of cation-anion combonations

Table 2: cation spot test results

Graph 1: chart of analysis scheme used during experiment

Calculations

Moles of substance = grams of substance / grams per mole = 36.65 g Fe(NO3)2 / 366.49 g/mol = .1 moles of Fe(NO3)2.

Molarity = moles of substance / Liters of solution = .1 moles Fe / 1 Liter solution = .1 molarity

Discussion

We found that the ore sample contained Barium and Iron. We found the Barium in our first test of our analysis scheme, the test was to add SO4 which forms a precipitate with Barium only. This formation of the precipitate confirmed Barium to be present in the ore. After decanting the supernatant, we performed more tests on the solution until we came to form a precipitate using C2O4 which only forms precipitates with Nickel and Iron. Because Nickel and Iron could not be separated using an anion we determined the substance to be Iron based on the color.

The tests confirmed our initial hypothesis that Iron would be present in the ore; however, it we did not suspect Barium to be present as well. Though our findings appear to be conclusive, it would be best to perform the tests again to be sure of the results.

One key problem that could have discredited our results entirely is that we were forced to recreate a new analysis scheme when our original scheme failed to be fruitful upon our first test. Based on the failure of our first scheme, it is possible that our second one could have failed without detection as well.

Another difficulty in the experiment was that two pairs of cations reacted the exact same way with all the anions as the other. To prevent this we would need to use more anions that would produce differing results so that we could separate these metals. With the added anions we would be able to determine if the final substance was in fact iron, or instead nickel. In the end it would be best to rerun the tests with more anions and a tested analysis scheme.

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