Stock Solution Calculator

To calculate molarity from percentage purity and density, use the formula: M = (% purity × density × 1000) / molar mass. For example, 37% HCl with density 1.18 g/mL and molar mass 36.46 g/mol gives: M = (37 × 1.18 × 1000) / 36.46 = 12.08 M. This weight percent to molarity conversion is essential for laboratory solution preparation from concentrated stock chemicals.

The formula for converting weight percent to molarity is: M = (wt% × density × 1000) / molecular weight. The multiplication by 1000 converts g/mL to g/L. This molarity calculation is crucial when preparing solutions from concentrated acids and bases where the label shows weight percent purity.

To calculate stock solution concentration from a concentrated acid like HCl, H₂SO₄, or HNO₃, enter the percentage purity, density (typically shown on the bottle), and molar mass. The calculator converts these to molarity automatically. For example, commercial 98% H₂SO₄ (density 1.84 g/mL) equals approximately 18.4 M.

Molarity (M) = moles of solute per liter of solution, while normality (N) = equivalents of solute per liter. For monoprotic acids like HCl, 1 M = 1 N. For diprotic acids like H₂SO₄, 1 M = 2 N. For triprotic acids like H₃PO₄, 1 M = 3 N. Enable Advanced Mode to calculate normality from molarity using the equivalents factor.

The C₁V₁ = C₂V₂ formula (also written as M₁V₁ = M₂V₂) relates stock and diluted concentrations. C₁/V₁ = stock concentration/volume, C₂/V₂ = target concentration/volume. To find volume of stock needed: V₁ = (C₂ × V₂) / C₁. This serial dilution calculation ensures accurate laboratory solution preparation.

To prepare a working solution from stock: 1) Calculate stock molarity from purity/density/molar mass, 2) Use C₁V₁ = C₂V₂ to find volume of stock needed, 3) Add that volume to a volumetric flask, 4) Dilute to final volume with solvent. This dilution factor approach is standard for preparing buffers and reagents.

Density matters because it provides the mass-to-volume conversion for the concentrated solution. Without density, you cannot determine how many grams of solute are in a milliliter. Since molarity requires moles per liter, and purity is given as weight percent, density bridges these units: mass = density × volume.

To calculate normality from molarity, multiply molarity by the number of reactive equivalents per molecule. For acids: equivalents = number of H⁺ ions donated (HCl = 1, H₂SO₄ = 2, H₃PO₄ = 3). For bases: equivalents = number of OH⁻ ions accepted (NaOH = 1, Ca(OH)₂ = 2). Enable Advanced Mode to enter equivalents for normality calculation.

The dilution factor (DF) indicates how much to dilute a stock solution. DF = Cstock / Cworking = Vfinal / Vstock. For example, to make 0.1 M from 12 M stock: DF = 12 / 0.1 = 120-fold dilution. The C₁V₁ = C₂V₂ equation directly gives you the volumes needed for any dilution factor.

To dilute a concentrated solution to a specific molarity: 1) Use the calculator to find your stock molarity from purity/density, 2) Enter target molarity and target volume, 3) The calculator uses V₁ = (C₂ × V₂) / C₁ to give you the exact volume of stock needed. Then add diluent to reach your final volume for accurate laboratory dilution.