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10th Class Science Periodic Classification of Elements Question Bank Periodic Classification of Elements

  • question_answer
    Three elements X, Y and Z form a m Dobereiner triad. Their atomic weights are in the ratio 5 : 11 : 17. If the sum of the atomic weights of extreme elements is 176, then find the atomic weights of X, Y and Z.                

    A)
    X Y Z
    40 80 176

    B)  
    X Y Z
    40 88 136

    C)  
    X Y Z
    40 80 120

    D)  
    X Y Z
    80 100 120

    Correct Answer: B

    Solution :

    Let the given ratio of atomic weights of X, Y, Z be 5x, 11 x, 17x respectively. Sum of extreme elements\[(5x+17x)=176\](given).                 \[22x=176,x=\frac{176}{22}=8\] \[\therefore \] At wt. of \[X=5\times 8=40,Y=11\times 8=88,\] \[\text{Z}=\text{17}\times \text{8}=\text{136}\].            


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