3 - Qualitative Analysis of Anions

3 - Qualitative Analysis of Anions - Experiment 3:...

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Experiment 3: Qualitative Analysis of Anions Chem 131: General Chemistry I Experiment 3 Qualitative Analysis of Anions Investigation of the qualitative tests for common anions. Determination of the anions present in a test solution. Page 1
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Qualitative Analysis of Anions Introduction Qualitative Analysis Qualitative Analysis involves taking unknown samples, often in solution, and finding out what they contain, but not how much the sample contains. Finding out how much of a substance a sample contains is Quantitative Analysis. This exercise in qualitative analysis will be carried out by performing a series of simple reactions in solution and observing the changes that take place. The presence, or absence, of the following six anions will be determined. CO 3 2– SO 4 2– SO 3 2– Cl NO 3 PO 4 3– The Test Reactions The reactions used to test for each of the six anions are shown by the following incomplete, unbalanced equations. 1. CO 3 2– (aq) + HCl(aq) CO 2 (g) + H 2 O(ℓ) + Cl - (aq) 2. SO 4 2– (aq) + BaCl 2 (aq) + HCl(aq) BaSO 4 (s) 3. SO 3 2– (aq) + HCl(aq) + K 2 Cr 2 O 7 (aq) Cr 3+ (aq) 4. Cl (aq) + AgNO 3 (aq) + HNO 3 (aq) AgCl(s) 5. NO 3 (aq) + NaOH(aq) + Al(s) NH 3 (g) 6. PO 4 3– (aq) + (NH 4 ) 2 MoO 4 (aq) (NH 4 ) 3 PO 4 •12MoO 3 (s) Three different tests will be carried out for each of these anions. Test 1: Carry out the test on a solution that is known to contain the anion. This is called the “Known” or “Positive” test. Test 2: Carry out the test on a solution that is known not to contain the anion. This test is called the “Control” or “Negative” test. Test 3: Carry out the test on an unknown solution. Compare the result of the test on the unknown solution to the “Known” and “Control” tests to determine if the anion being tested for is present in the unknown sample or absent from the unknown sample. A negative test result is just as valuable as positive test result. The computer report consists of a table with six entries. You need to enter either P for the presence of an anion, or A for the absence of an anion in your unknown solution. Laboratory Risk Assessment Sheet
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3 - Qualitative Analysis of Anions - Experiment 3:...

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