You need to make an aqueous solution of 0.121 M magnesium chloride for an experiment in lab, using a 250 mL volumetric flask. How much solid magnesium chloride should you add ?
How many moles do you need? That is M x L = ??
moles = grams/molar mass. You know moles and molar mass, solve for grams.
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To calculate the amount of solid magnesium chloride needed to make a 0.121 M solution, we need to use the formula:
Molarity (M) = moles of solute / volume of solution (in liters)
Given:
Molarity (M) = 0.121 M
Volume of solution = 250 mL = 0.25 L
We need to rearrange the formula to solve for moles of solute:
Moles of solute = Molarity (M) x Volume of solution (in liters)
Moles of solute = 0.121 M x 0.25 L
Moles of solute = 0.03025 moles
Now, we need to convert moles into the mass of magnesium chloride using its molar mass. The molar mass of magnesium chloride is 95.211 g/mol.
Mass of magnesium chloride = Moles of solute x Molar mass of magnesium chloride
Mass of magnesium chloride = 0.03025 moles x 95.211 g/mol
Mass of magnesium chloride = 2.8836 g
Therefore, you need to add approximately 2.8836 grams of solid magnesium chloride to the 250 mL volumetric flask to make a 0.121 M aqueous solution.