Question

On the first day of your new job as a chemist, you are given a bottle of magnesium sulfate and asked to make 30 mL of 0.3 M MgSO4. The formula on the bottle is MgSO4∗7H2O (also known as Epsom salt). Calculate the amount of salt you need (in milligrams).

Answer 1

Answer:

The answer to your question is 15500 mg of MgSO₄ 7H₂O

Explanation:

Data

Volume = 30 ml

Concentration = 0.3 M

Formula MgSO4∗7H2O

Process

1.- Calculate the number of moles needed

 Molarity = moles / volume

Solve for moles

 moles = Molarity x volume

Substitution

 moles = 0.3 x 0.03 l

 moles = 0.009 moles of MgSO₄

2.- Calculate the molecular mass of MgSO4∗7H2O

molecular mass = 24 + 32 + 64 + 14 + 112

                           = 246 g

3.- Get the proportion MgSO4 :7H2O, this proportion is 1 : 7

4.- Calculate the amount of MgSO4∗7H2O

    $0.009 mol of MgSO4 \frac{7 MgSO4 7H2O}{1 mol MgSO4} \frac{246 g MgSO4 7H2O}{1 mol MgSO4 7H2O}$

Simplification

   15.5 g = 15500 mg