Convert 3.45g of magnesium chloride to moles

Answer 1

Magnesium chloride (MgCl₂) has a molecular weight of 95.2 g/mol:

Cl₂ = 2 chlorine atoms: 35.45 g/mol × 2 = 70.9 g/mol

Mg = 1 magnesium atom: 24.3 g/mol

24.3 g/mol + 70.9 g/mol = 95.2 g/mol

To calculate the number of moles are in 3.45 grams of MgCl₂, we will do a stoichiometric conversion:

3.45 g MgCl₂ × 1 mol MgCl₂/95.2 g MgCl₂ = 0.0362 moles MgCl₂

The reason why we used the reciprocal 95.2 grams was to move the grams unit into the denominator. This would then cancel out grams on both sides, leaving moles in the numerator for the final answer. It may be more helpful for you to visualize this solution if you write the fractions vertically instead of horizontally like I did.