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1. Some basic concept of chemistry — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistry1. Some basic concept of chemistry1 Mark
MCQ
An element, $X$ has the following isotopic composition :

$^{200}X \,:\, 90\%$       $^{199}X\, :\, 8.0\%$       $^{202}X\, :\, 2.0\%$

The weighted average atomic mass of the naturally occurring element $X$ is closest to......$amu$

  • A
    $201$
  • B
    $202$
  • C
    $199 $
  • ✓
    $200$
✓

Answer

Correct option: D.
$200$
d
Weight of $^{200} X=0.90 \times 200=180.00 u$

Weight of $^{199} X=0.08 \times 199=15.92 u$

Weight of $^{202} X=0.02 \times 202=4.04 u$

Total weight $=199.96 \approx 200 u$

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