Grams for Target Molarity Calculator
Work out how many grams of solute to weigh out to make a solution of a target molarity and volume from the compound’s molar mass.
How it works
grams = molarity (mol/L) × volume (L) × molar mass (g/mol)
To prepare a solution of a known molarity you first find how many moles of solute the target concentration and volume require, then convert that mole count into a weighable mass using the molar mass. Dissolve the weighed solid and dilute to the final volume — usually in a volumetric flask — to hit the concentration precisely. It is the everyday recipe for making up a standard solution.
Worked example
To make 500 mL of 0.50 M NaCl (molar mass 58.44 g/mol): moles = 0.50 × 0.500 = 0.25 mol, so grams = 0.25 × 58.44 = 14.61 g. Weigh 14.61 g of NaCl and dilute to 500 mL.
Sources: Molar concentration — Wikipedia
Frequently asked questions
Do I add water to the volume or dissolve in that volume?
Dissolve the solute in less water first, then top up to the final volume in a volumetric flask. Adding solute to a full volume overshoots the target volume and dilutes the concentration.
Where do I find the molar mass?
Sum the atomic masses of every atom in the formula from the periodic table, or use a molar-mass calculator. For NaCl it is 22.99 + 35.45 = 58.44 g/mol.
How do I make a more dilute solution from this one?
Use C₁V₁ = C₂V₂ to figure out how much of the stock to take and how much water to add — a dilution calculator does this directly.
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This calculator is for educational purposes. Double-check important results before acting on them.