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Some Basic Concepts of Chemistry — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistrySome Basic Concepts of Chemistry1 Mark
MCQ
The number of atoms present in one mole of an element is equal to Avogadro number. Which of the following element contains the greatest number of atoms?
  • A
    $\ce{4g He}$
  • B
    $\ce{46g Na}$
  • C
    $\ce{0.40g Ca}$
  • ✓
    $\ce{12g He}$
✓

Answer

Correct option: D.
$\ce{12g He}$
As we new that
Number of atoms $=\text{Mol.}\times\text{N}_\text{A}$
Number of moles $=\frac{\text{wt.}}{\text{Mol. wt.}}$
  1. $4\text{g}\ \text{He}=\frac{4}{4}-1\ \text{mole}$
  2. $46\text{g}\ \text{Na}=\frac{46}{23}=2\ \text{moles}$
  3. $0.40\text{g}\ \text{Ca}=\frac{0.40}{40}=0.01\ \text{mole}$
  4. $12\text{g}\ \text{He}=\frac{12}{4}=3\ \text{moles}$
Hence, $12 \ \ce{g  He}$ of $\ce{He}$ contains the greatest number of atoms.

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