Question

A student is given an unknown aqueous sample containing one of the three ions, A Ba?" or Mg2+ There is limited unknown so the student can only run a couple of tests. Select all tests, based on the table above, that will not provide useful information, even when performed correctly to identify ions present in the unknown Na, SO NOOH Na,CO 0/2 pts incorrect Question 9 The TA then informs the class that some unknown's may have only contained distilled water. Which single test should the student perform to make sure they have an unknown lon in their sample? NOOH • Na2SO4 Nasco

Answer 1

The tests that will not provide useful information to identify the unknown ion are Na2SO4 and NaCO3. To confirm the presence of an unknown ion in the sample, the student should perform the test with NaOH.

Step-by-step explanation:

The tests that will not provide useful information to identify the ion in the unknown sample are Na2SO4 and NaCO3. These tests will not react with the ions A, Ba2+, or Mg2+ and therefore will not provide any useful information about the identity of the ion.

To confirm the presence of an unknown ion in the sample, the student should perform the test with NaOH. Adding NaOH to the sample will neutralize any ammonium ions present, producing NH3 gas. The presence of NH3 gas can be detected by its characteristic odor or by using a litmus paper test.

Answer 2

To identify the presence of an ion in the unknown aqueous sample, the student can perform a precipitation reaction using sodium sulfate, which would form a white precipitate of BaSO4 if Ba2+ is present.

Step-by-step explanation:

The student is tasked with identifying the presence of an unknown ion in an aqueous sample which could be Na+, Ba2+, or Mg2+. Given the limited sample, the student can perform only a couple of tests from a list to discern which ion, if any, is present. However, without seeing the table mentioned in the question, we cannot discern which tests will not be useful. To confirm the presence of an ion in general, the student should perform a test that applies broadly to all potential ions.

To check if the unknown sample contains an ion, a single test such as a flame test could be used for alkali metals, which would produce characteristic colors. However, this would not be useful for Ba2+ or Mg2+. Therefore, adding a reagent that forms a precipitate with one or more of the ions mentioned, such as sodium sulfate (Na2SO4), would be a good general test since Barium will form a white precipitate of barium sulfate (BaSO4), which is insoluble in water.