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Question Video: Determining Which Anion Concentrated Sulfuric Acid Does Not Test For Chemistry

Which of the following anions is not usually tested for by using concentrated sulfuric acid? [A] Nitrate (NO₃⁻) [B] Iodide (I⁻) [C] Chloride (Cl⁻) [D] Sulfite (SO₃²⁻) [E] Bromide (Br⁻)

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Video Transcript

Which of the following anions is not usually tested for by using concentrated sulfuric acid? (A) Nitrate, NO31−; (B) iodide, I1−; (C) chloride, Cl1−; (D) sulfite, SO32−; or (E) bromide, Br1−.

There are a variety of qualitative tests in chemistry that can be used to indicate the presence of specific ions in substances. In the presence of particular anions, these tests produce very visible results. A color change, new odor or gas, temperature change, or formation of a precipitate are all examples of these observable changes. There are several compounds used to test for different anions, but our question asks about the reagent, concentrated sulfuric acid. The correct sequence to test for anions is first adding dilute hydrochloric acid, then concentrated sulfuric acid, and finally a barium chloride solution.

Let’s have a look at the ions that can be detected with each testing reagent to determine which anions are not detected by sulfuric acid. Typically, dilute hydrochloric acid produces visible reactions when carbonate, sulfite, bicarbonate, sulfide, thiosulfate, and nitrate ions are present. Concentrated sulfuric acid is then used to test for halide ions, such as fluoride, chloride, bromide, and iodide ions, as well as nitrate ions. Finally, barium chloride is used to test for the presence of sulfate and phosphate ions.

This question is asking us which of the anions’ presence would not usually be tested with concentrated sulfuric acid. Since nitrate, iodide, chloride, and bromide ions are all tested using sulfuric acid, we can eliminate answer choices (A), (B), (C), and (E).

Sulfite ions are generally tested for by using dilute hydrochloric acid. Therefore, the anion that is not usually tested for by using concentrated sulfuric acid is answer choice (D): sulfite, SO32−.

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