Question

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

Answer 1

`"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 `= 6.022*10^23` particles of a substance per mol of that substance

`8.0"g Ca" * (1 "mol Ca")/(40.08"g Ca")*(6.022*10^23"atoms of Ca")/(1 "mol Ca") = 1.2*10^23"atoms of Ca"`

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

`1.2*10^23"atoms of Mg"*(1 "mol Mg")/(6.022*10^23"atoms of Mg")*(24.31"g Mg")/(1"mol Mg") = 4.9"g Mg"`

You can also eliminate the step of converting to atoms, as a mol of any substance contains `6.022*10^23` particles of that substance