7th Class Science Acids, Bases and Salts Question Bank Acids, Bases and Salts

  • question_answer A blue litmus paper was first dipped I dilute hydrochloric acid and then in dilute sodium hydroxide solution. It was observed that the colour of the litmus paper:

    A) changed to red

    B) changed first to red and then to blue

    C) changed blue to colourless

    D) remained blue in both solutions.

    Correct Answer: B

    Solution :

    When blue litmus paper is dipped in dilute hydrochloric acid it becomes red. If red litmus paper is dipped in dilute sodium hydroxide solution it becomes blue.


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