# Solution Preparation Calculator

Free solution preparation calculator. Calculate how much solute to weigh to make a solution of desired molarity and volume. Step-by-step instructions.

## What this calculates

Calculate the mass of solute needed to prepare a solution of a given molarity and volume. Enter the desired concentration, volume, and molar mass to get precise weighing instructions.

## Inputs

- **Desired Molarity** (M) — min 0 — Target concentration in mol/L.
- **Desired Volume** (mL) — min 0 — Total volume of solution to prepare in milliliters.
- **Solute Molar Mass** (g/mol) — min 0.001 — Molar mass of the solute (e.g., NaCl = 58.44 g/mol).
- **Solute Purity** (%) — min 1, max 100 — Purity of the solute (100% for pure reagents).
- **Common Solute (reference)** — options: Custom (enter molar mass above), NaCl - 58.44 g/mol, NaOH - 40.00 g/mol, HCl - 36.46 g/mol, KCl - 74.55 g/mol, CaCl₂ - 110.98 g/mol, Glucose - 180.16 g/mol, Sucrose - 342.30 g/mol, Na₂CO₃ - 105.99 g/mol — Select for automatic molar mass.

## Outputs

- **Solute to Weigh** (g) — Mass of solute to weigh out.
- **Moles of Solute** (mol) — Moles of solute needed.
- **Adjusted for Purity** (g) — Mass accounting for impurity.
- **Preparation Instructions** — formatted as text — Step-by-step instructions for preparing the solution.

## Frequently Asked Questions

**Q: How do I prepare a molar solution?**

A: Calculate mass needed (mass = M × V × molar mass), weigh the solute, dissolve in a small amount of solvent, transfer to a volumetric flask, and add solvent to the desired final volume.

**Q: Why do I dissolve first then add to volume?**

A: Dissolving the solute can change the total volume (due to volume of dissolution). By dissolving first and then bringing to final volume in a volumetric flask, you ensure the exact concentration.

**Q: What is purity correction?**

A: If your solute is not 100% pure (e.g., 95% NaOH), you need to weigh more to account for the impurity. Adjusted mass = pure mass / (purity/100).

**Q: What is a standard solution?**

A: A standard solution is one whose concentration is accurately known. Primary standards (like sodium carbonate or potassium hydrogen phthalate) can be weighed directly. Secondary standards must be standardized by titration.

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Source: https://vastcalc.com/calculators/chemistry/solution-preparation
Category: Chemistry
Last updated: 2026-04-21