What mass of iodine would react with 48 grams of magnesium to make magnesium iodide?

501.248 g

Explanation:

The chemical equation of the reaction between magnesium and iodine is

Mg  +  I₂  ⇒  MgI₂

Convert grams of magnesium to moles.  The molar mass is 24.305 g/mol.

(48 g)/(24.305 g/mol) = 1.975 mol

To convert moles of magnesium to moles of iodine, you need to use stoichiometry.  Looking at the chemical equation, you can see that for every mole of magnesium, one mole of iodine is needed.  This means that the moles required from each molecule is equal.

1.975 mol Mg  =  1.975 mol I₂

Now, convert moles of iodine to grams.  The molar mass is 253.8089 g/mol.

(1.975 mol) × (253.8089 g/mol) = 501.248 g

You will need 501.248 g of iodine for the reaction to occur.