How do I calculate molarity when using hydrated salts?

Use the molar mass of the hydrated compound, not the anhydrous form. For CuSO 4 ·5H 2 O, the molar mass is 249.69 g/mol (not 159.61 g/mol for anhydrous CuSO 4 ). The water of crystallization adds to the mass you weigh but does not change the moles of CuSO 4 in solution. Simply enter 249.69 as the molar mass in the calculator.

How do I calculate the molarity of mixed solutions?

For two solutions of the same solute mixed together, calculate total moles and divide by total volume. Total moles = (M 1 × V 1 ) + (M 2 × V 2 ). Total volume = V 1 + V 2 assuming volumes are additive. Mixture molarity = total moles / total volume. For different solutes, calculate each concentration independently.

Molarity Calculator – Solution Concentration & Dilution

Use the standard formula M = (wt% × density × 1000) / molar mass. This formula converts weight-based concentration (grams of solute per 100 g solution) into moles per liter by using density to determine volume. Example (37% HCl): wt% = 37, density = 1.18 g/mL, molar mass = 36.46 g/mol. M = (37 × 1.18 × 1000) / 36.46 = 12.08 M. The calculator performs this conversion instantly and accurately.

Weight percent is mass-based while molarity is volume-based, so density is required for conversion. Formula: M = (wt% × density × 1000) / molar mass. Common conversions:
37% HCl → 12.08 M.
98% H₂SO₄ → 18.39 M.
50% NaOH → 19.06 M.
Glacial acetic acid → 17.45 M.

Use the Quick Fill feature for fast, pre-verified values.

Concentrated reagents show wt% purity and density on the label. Apply the formula M = (wt% × density × 1000) / molar mass using the exact values provided on your bottle. Standard reference values:
HCl 37% → 12.08 M.
H₂SO₄ 98% → 18.39 M.
HNO₃ 70% → 15.67 M.
NaOH 50% → 19.06 M.

Always prefer the values printed on your specific reagent bottle for highest accuracy.

The dilution formula C₁V₁ = C₂V₂ conserves the number of moles of solute. To find stock volume needed: V₁ = (C₂ × V₂) / C₁. Examples: 500 mL of 0.1 M HCl from 12.08 M stock → 4.14 mL stock. 1 L of 1 M H₂SO₄ from 18.39 M stock → 54.37 mL stock. The "Volume Needed" mode in this calculator applies the formula automatically.

Molarity (M) = moles of solute per liter of solution. Normality (N) = number of reactive equivalents per liter of solution. Relationship: N = M × n, where n is the equivalents factor. Common n values: HCl = 1, H₂SO₄ = 2, H₃PO₄ = 3, NaOH = 1. Normality is especially useful in titrations. Enable Advanced Mode to calculate both units simultaneously.

Determine stock molarity (use Quick Fill or the formula). Calculate required stock volume with C₁V₁ = C₂V₂. Add roughly half the final volume of distilled water to a volumetric flask. Slowly add the concentrated stock (acid to water only). Cool if necessary, then top up to the final volume and mix well. Label properly. This safe method is used for preparing 0.1 M, 1 M, and other common laboratory solutions.

Weight percent describes mass of solute per mass of solution, while molarity requires moles per volume (liter) of solution. Density bridges this gap by converting mass of solution into volume. Without density, accurate conversion is impossible. Even small variations in density can noticeably affect the calculated molarity.

Use the simple formula N = M × n, where n is the equivalents factor based on the number of reactive H⁺ or OH⁻ ions. Examples:
12.08 M HCl × 1 = 12.08 N.
18.39 M H₂SO₄ × 2 = 36.78 N.
19.06 M NaOH × 1 = 19.06 N.

This calculator computes normality automatically in Advanced Mode.

Dilution factor (DF) = initial concentration / final concentration = final volume / stock volume. Examples: 10-fold: 1 part stock + 9 parts diluent. 100-fold: 1 part stock + 99 parts diluent. For serial dilutions, multiply the individual factors. The calculator handles all dilution calculations instantly.

Calculate the required stock volume using V₁ = (C₂ × V₂) / C₁. Then follow safe lab practice: Start with half the final volume of water in the flask. Add the concentrated reagent slowly (acid to water). Cool if heat is generated. Make up to final volume and mix thoroughly. The calculator provides exact volumes for any target concentration.

Use the molar mass of the hydrated compound, not the anhydrous form. For CuSO₄·5H₂O, the molar mass is 249.69 g/mol (not 159.61 g/mol for anhydrous CuSO₄). The water of crystallization adds to the mass you weigh but does not change the moles of CuSO₄ in solution. Simply enter 249.69 as the molar mass in the calculator.

Molarity (M) is moles of solute per liter of solution. Molality (m) is moles of solute per kilogram of solvent. Molarity changes with temperature because volume expands. Molality is temperature-independent because mass does not change. Use molarity for most lab work, titrations, and spectrophotometry. Use molality for freezing point depression, boiling point elevation, and other colligative property calculations.

Always add concentrated acid to water slowly while stirring, never the reverse. Dilution of concentrated acids generates significant heat. Adding water to acid can cause rapid boiling and dangerous splashing. Wear safety goggles, a lab coat, and chemical-resistant gloves. Work in a fume hood for volatile acids like HCl and HNO₃. Use this calculator to determine the exact volumes needed before you start.

For two solutions of the same solute mixed together, calculate total moles and divide by total volume. Total moles = (M₁ × V₁) + (M₂ × V₂). Total volume = V₁ + V₂ assuming volumes are additive. Mixture molarity = total moles / total volume. For different solutes, calculate each concentration independently.

Standard reference values:
Hydrochloric acid (37% wt) = 12.08 M.
Sulfuric acid (98%) = 18.39 M.
Nitric acid (70%) = 15.67 M.
Phosphoric acid (85%) = 14.63 M.
Glacial acetic acid (99.7%) = 17.45 M.
Ammonium hydroxide (28%) = 14.53 M.
Sodium hydroxide (50%) = 19.06 M.

Always verify the exact wt% and density printed on your specific reagent bottle, as values vary slightly between manufacturers.

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