Question

If one mole of Carbon contains x atoms, then the number of atoms in 12 g of Magnesium is:
1. 2x
2. 0.5x
3. 0.25x
4. 4x

Answer 1

Correct Answer - Option 2 : 0.5x

The correct answer is option 2) i.e. 0.5x

CONCEPT:

• Avogadro's number: The number of units present in one mole of a given substance is called the Avogadro's number.
  • Avogadro's number (NA) is equal to 6.022140857 × 1023.
  • This number also called Avogadro's constant is equal to the number of atoms present in 12 grams of Carbon-12.
  • Mole is a fundamental unit of measure of the amount of a substance.
  • For atoms, the mass of Avogadro's number of particles is equal to their atomic mass in grams.
  • For molecules, the mass of Avogadro's number of particles is equal to their molecular mass in grams.

EXPLANATION:

​1 mole of C = x atoms = N_A atoms. 

We know that NA = the number of atoms present in 12 grams of Carbon-12

So,  x = N_A

The atomic mass of Mg is 24 g/mol i.e. 1 mole of Mg = 24 g = x atoms

The number of moles in 12 g of Mg = 12/24 = 0.5 moles

1 mole of Mg → x atoms

0.5 mole of Mg → 0.5x atoms

Therefore, 12 g of Magnesium has 0.5x atoms.