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8th Class Science Combustion and Flame Question Bank Combustion and Flame HOTS Objective Problems

  • question_answer
    Swati took two glass plates I and II. She introduced them to the-different zones of a flame (as shown in the figure). She held them there with a pair of tongs for about 10 seconds. She observes that a circular-blackish ring has developed on plate I, while no such blackish ring is observed on plate II. From Swati's experiment, it can be concluded that ______i______ zone is the zone containing unburnt particles, and the ___ii___ zone is the zone of complete combustion.
    The information in which alternative completes the given statement?

    A)  i-outermost, ii-Innermost

    B)  i-Innermost, ii-Outermost

    C)  i-Innermost, ii-Middle.

    D)  i-Middle, ii-Innermost

    Correct Answer: B

    Solution :

      A circular-blackish ring has developed on plate I when it is held near the innermost zone. This indicates that the innermost zone contains unburnt carbon particles. On the other hand, no such ring is observed on plate II when it is held near the outermost zone. This indicates that the outermost zone contains no unburnt particles. Hence, the outermost zone is the zone of complete combustion. The correct answer is B.


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