What mass of magnesium contains the same number of atoms as 8.0g of calcium?

1 Answer

4.9 g Mg

Explanation:

Molar Mass of Magnesium (Mg): 24.31 g/mol
Molar Mass of Calcium (Ca): 40.08 g/mol

Avogadro's constant =6.0221023 particles of a substance per mol of that substance

8.0g Ca1mol Ca40.08g Ca6.0221023atoms of Ca1mol Ca=1.21023atoms of Ca

The number of atoms of Mg should be the same as the number of atoms of Ca, so:

1.21023atoms of Mg1mol Mg6.0221023atoms of Mg24.31g Mg1mol Mg=4.9g Mg

You can also eliminate the step of converting to atoms, as a mol of any substance contains 6.0221023 particles of that substance