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Some Basic Concepts of Chemistry question

2007 · Q92
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Some Basic Concepts of Chemistry question

2007 · Q92

NEETChemistrySome Basic Concepts of ChemistryMCQ+4 / −1
An element, X has the following isotopic composition:
200X : 90%  199X : 8.0%  202X : 2.0%

The weighted average atomic mass of the naturally occuring element X is closest to
  1. A
    201 amu
  2. B
    202 amu
  3. C
    199 amu
  4. D
    200 amu
View written solutionFree

Correct answer: D

Average isotope mass of X

= 200×90+199×8+202×290+8+2{{200 \times 90 + 199 \times 8 + 202 \times 2} \over {90 + 8 + 2}}90+8+2200×90+199×8+202×2​

= 18000+1592+404100{{18000 + 1592 + 404} \over {100}}10018000+1592+404​

= 199.96 a.m.u ≈\approx≈ 200 a.m.u

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