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Some Basic Concepts of Chemistry question

2016 · Q79
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Some Basic Concepts of Chemistry question

2016 · Q79

NEETChemistrySome Basic Concepts of ChemistryMCQ+4 / −1
Suppose the elements X and Y combine to form two compounds XY2 and X3Y2. When 0.1 mole of XY2 weights 10 g and 0.05 mole of X3Y2 weighs 9 g, the atomic weights of X and Y are
  1. A
    40, 30
  2. B
    60, 40
  3. C
    20, 30
  4. D
    30, 20
View written solutionFree

Correct answer: A

Assume the atomic weight of element X is x and element Y is y.

For XY2, n=wMol.  wt.n = {w \over {Mol.\,\,wt.}}n=Mol.wt.w​

0.1=10x+2y0.1 = {{10} \over {x + 2y}}0.1=x+2y10​

⇒x+2y=100.1=100 \Rightarrow x + 2y = {{10} \over {0.1}} = 100⇒x+2y=0.110​=100    ...(i)

For X3Y2, n=wMol.  wt.n = {w \over {Mol.\,\,wt.}}n=Mol.wt.w​

0.05=93x+2y0.05 = {9 \over {3x + 2y}}0.05=3x+2y9​

⇒3x+2y=90.05=180 \Rightarrow 3x + 2y = {9 \over {0.05}} = 180⇒3x+2y=0.059​=180    ...(ii)

On solving equations (i) and (ii),

we get y = 30 g mol-1

Put the value of y in equation. (i)

x + 2(30) = 100

⇒\Rightarrow⇒ x = 100 - 60 = 40 g mol-1

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