To solve for this problem, we need to employ the molar mass - moles ratio. Remember that:

`Number of mol es of any compound = (Given mass)/(molar mass)`

Since we are after to the given mass, we can have it as:

`Given mass = Molar mass * Number of mol es`

`Given mass = (4.23 mol es Magn esium s u l f a te)*(120.366 (grams)/(mol e))`

Given mass = 509.15 Grams Magnesium sulfate

Note: The molar mass of Magnesium sulfate is 120.366