Explain how you would decide which represents a greater mass: 3.25 x 1022 atoms of Ca or 2.45 grams of Mg?

Mg

Explanation:

Given data:

Number of atoms of Ca = 3.25×10²²

Mass of Mg = 2.45 g

which has greater mass = ?

Solution:

1 mole = 6.022 ×10²³ atoms

3.25×10²² atoms × 1 mol/6.022 ×10²³ atoms

0.54×10⁻¹ mol

0.054 mol

Mass of Ca:

Mass = number of moles × molar mass

Mass = 0.054 mol × 40 g/mol

Mass = 2.16 g

Mass of Mg = 2.45 g

The  3.25×10²² atoms of Ca has 2.16 g mass while the other given Mg has 2.45 g mass. Thus Mg has greater mass.