Tag: empirical formula, percentage composition and molecular formula

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Multiple choice chemistry the language of chemistry percent composition percentage composition and empirical formula empirical formula, percentage composition and molecular formula

Calculate the number of molecules present in $0.5$ moles of magnesium oxide $\left( MgO \right) $. 

[Atomic weights :  $Mg=24, O=16$]

  1. $14.09\times { 10 }^{ 23 }$ molecules
  2. $3.0115\times { 10 }^{ 23 }$ molecules
  3. $30.12\times { 10 }^{ 23 }$ molecules
  4. $14.09\times { 10 }^{ -23 }$ molecules
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B Correct answer
Explanation
1 mole of MgO contains Avogadro's number of molecules which is $ \displaystyle 6.023 \times 10^{23}$ molecules.

0.5 mole of MgO will contain $ \displaystyle 0.5 \times 6.023 \times 10^{23}=3.0115 \times 10^{23}$ molecules.