Question

1. Janine is asked to make up a solution of 10% MgS04. She has a bottle that is labeled MgS04 – 5H20. How many grams will she need to make up this solution? Describe the how she will make up this solution, including instrumentation, pipettes and glassware.

Answer 1

Molecualr weight of MgSO₄.5H₂O = 210.44 g/mol

Molecualr weight of MgSO₄ = 120.36 g/mol

10 % MgSO₄ = 10 g in 100 mL or 100 g in 1 liter

10 g of MgSO₄ = 10 g / 120.36 g/mol = 0.0831 mol

hence 0.0831 moles of MgSO₄.5H₂O = 210.44 g/mol x 0.0831 mol = 17.48 g in 100 mL .

weigh 17.48 g of MgSO4. 5H2O in a labeled bottle and dissove in small amount of water and make up the solution 100 mL by using pipette.