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9th Class Science Atoms and Molecules Question Bank Atoms and Molecules

  • question_answer
    Four different experiments were conducted in the following ways :
    I. 3 g of carbon was burnt in 8 g of oxygen to give 11 g of \[\text{C}{{\text{O}}_{\text{2}}}\].
    II. 1.2 g of carbon was burnt in air to give 4.2 g of \[\text{C}{{\text{O}}_{\text{2}}}\].
    III. 4.5 g of carbon was burnt in enough air to give 11 g of \[\text{C}{{\text{O}}_{\text{2}}}\].
    IV. 4 g of carbon was burnt in oxygen to form 30.3 g of \[\text{C}{{\text{O}}_{\text{2}}}\].
    Law of constant proportions is illustrated in experiment(s)

    A) I and III                       

    B) II and III          

    C) IV only

    D)        I only.

    Correct Answer: D

    Solution :

    According to law of constant proportions, the ratio of carbon and oxygen by weight should always be 3 : 8 in\[\text{C}{{\text{O}}_{\text{2}}}\]. In experiment I - C : 0 = 3 : 8 In experiment II - C : 0 = 1.2 : 3 In experiment III - C : 0 = 4.5 : 6.5 In experiment IV - C : 0 = 4 : 26.3


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