Complete Question:
What mass of magnesium bromide would be required to prepare 720mL of a 0.0939M aqueous solution?
Answer:
Molarity is calculated using following formula,
Molarity = Moles / Volume of Solution ---- (1)
Data Give;
Molarity = 0.0939 mol.L⁻¹
Volume = 720 mL = 0.72 L
Solving eq.1 for Moles,
Moles = Molarity × Volume
Moles = 0.0939 mol.L⁻¹ × 0.72 L
Moles = 0.0676 moles
Now convert Moles into Mass using following formula,
Moles = Mass / M.Mass
Solving for Mass,
Mass = Moles × M.Mass
Mass = 0.0676 mol × 184.113 g.mol⁻¹
Mass = 12.44 grams
