Question

You are given 1.000 grams of hydrated Magnesium Sulfate (MgSO4*XH20). You place it into a crucible and heat it up past 100 C so that the water evaporates from the hydrated salt. Once you are done, the mass of the dry anhydrous Magnesium Sulfate is 0.488 grams.

How many molecules of water are attached to each atom of Magnesium?
show work?

Answer 1

MgSO4. 7H2O

There are seven water molecules attached to the hydrated salt.

Step-by-step explanation:

From the equation;

Number of moles of hydrated salt = number of moles of anhydrous salt, we obtain:

Mass of hydrated salt/ molar mass of hydrated salt = mass of anhydrous salt/ molar mass of anhydrous salt

From the question;

Mass of hydrated salt = 1.000g

Molar mass of hydrated salt = 120.366 +18x gmol-1

Mass of anhydrous salt= 0.488g

Molar mass of anhydrous salt= 120.366 gmol-1

Substituting into the equation above;

1.000/120.366 +18x = 0.488/120.366

1.000/120.366 +18x = 0.004

1.000= 0.004 (120.366 +18x)

1.000= 0.48 + 0.072x

1.000 - 0.48 = 0.072x

0.52= 0.072x

x= 0.52/0.072

x=7

Therefore the hydrated salt is MgSO4. 7H2O