Question detail
A student is testing sulfate ion. Which choice keeps the observation and conclusion correctly linked?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Identification of ions by chemical and spectroscopic means
Question
- A. To prevent the formation of a white precipitate of barium hydroxide
- B. To ensure that carbonate ions are not present in the solution
- C. To stop the formation of a white precipitate of barium carbonate
- D. To dissolve any existing barium sulfate in the sample
Answer
The correct answer is To stop the formation of a white precipitate of barium carbonate. It matches sulfate ion because the evidence is barium chloride after acidifying and the expected result is white precipitate.
Explanation
The correct option is To stop the formation of a white precipitate of barium carbonate. The important distinction is that sulfate ion must be identified from barium chloride after acidifying; answers that swap in a different test or result do not match Sulfate ions. Other options are weaker when they confuse gas tests, flame colours, ion-test precipitates, chromatography evidence, or pure-substance/formulation wording.
Common mistake
Acidification Step Confusion
Students often forget to acidify the sample before adding barium chloride solution, leading to incorrect results.
Correct this by using the approved Sulfate ions context: Explain that the sample is acidified before adding barium chloride solution. Name the correct test or chemistry idea, state the observation accurately, and then give the conclusion supported by that evidence. Do not swap gas tests, flame tests, cation tests, anion tests, chromatography terms, pure substances, and formulations.
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