68th BPSC Prelims (2023), question 91

🔬 Science & Technology

  1. You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. Which of them will turn red litmus to blue?

    1. Acid
    2. Base
    3. Distilled water
    4. More than one of the above
    5. None of the above
    Show answer

    Answer: B — Base

    A basic (alkaline) solution turns red litmus blue; an acid does the reverse, turning blue litmus red. Distilled water is neutral and leaves litmus unchanged, so only the base produces the colour change asked about.

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