Video Transcript
Which of the following test tubes
shows the likely result of adding a solution of acidified barium chloride to a
solution of sodium sulfate?
Adding acidified barium chloride is
an example of a qualitative test that chemists use to determine the presence of
certain anions or cations within substances. These tests work by generating
highly visible reactions with observable changes, such as color change, new odor or
gas, temperature change, or formation of a precipitate.
As there are many different anions
we can test for, it is important that a structured approach to testing is taken when
administering primary tests. The first testing reagent we use
when identifying anions present is dilute hydrochloric acid. This test is used to identify
carbonate, sulfite, bicarbonate, sulfide, thiosulfate, and nitrate anions. If the unknown anion has not been
identified at this stage from distinguishable observations, concentrated sulfuric
acid is added. Observations at this stage can
detect the halide ions and nitrate ions.
If the anion has still not been
identified, the final testing reagent we use is a barium chloride solution. Barium chloride is used to test for
sulfate and phosphate ions. If sulfate or phosphate anions are
present in the tested substance, a white precipitate will be formed. To differentiate between the
precipitates formed by sulfate and phosphate ions, further confirmatory tests are
administered.
The question states that the
solution tested is sodium sulfate. Since this solution would contain
sulfate anions, we would expect a white precipitate to be formed in this primary
test. Therefore, the test tube that shows
the likely result of adding a solution of acidified barium chloride to a solution of
sodium sulfate is answer choice (C).
