Fill in every field except the one you want — the empty field is solved for.
Molarity = 0.4 M
- Convert grams to moles: 5.844 g ÷ 58.440 g/mol =
0.1 mol - Convert volume to litres: 250 mL ÷ 1000 =
0.25 L - M = n ÷ V = 0.1 mol ÷ 0.25 L =
0.4 mol/L
How it works
Molarity mode solves M = n / V. When the amount is in grams, the solute's formula is used to find its molar mass and convert to moles first; volumes in mL are divided by 1000. Dilution mode solves C₁V₁ = C₂V₂ and also reports how much solvent to add, and it refuses inputs where the "diluted" solution would be more concentrated than the stock.
Frequently asked questions
- What is molarity?
- Molarity (M) is moles of solute per litre of solution. A 1 M sodium chloride solution contains 1 mol (58.44 g) of NaCl in every litre of the final solution.
- How do I make a solution of a given molarity?
- Multiply molarity by volume in litres to get moles, then by molar mass to get grams. For 250 mL of 0.40 M NaCl: 0.40 × 0.250 = 0.100 mol, × 58.44 = 5.84 g. Dissolve it and add water up to 250 mL total — not 250 mL of water plus the solid.
- How does the dilution formula work?
- Adding solvent does not change the number of moles of solute, so C₁ × V₁ (moles before) equals C₂ × V₂ (moles after). Any three values give the fourth, and the volumes just need to share a unit.
- Is molarity the same as molality?
- No. Molarity is moles per litre of solution; molality is moles per kilogram of solvent. Molality does not change with temperature, which is why it is used for boiling-point and freezing-point calculations.
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