Molarity Calculator
Calculate solution molarity, moles, and mass for chemical preparation.
Calculator
No signup required. Results are indicative—verify for your standards.
Moles: 1.0000 mol
Molarity: 0.5000 M (mol/L)
Formula
Molarity (M) = Moles of solute / Volume of solution (L). Moles = Mass (g) / Molar mass (g/mol). Mass required = Molarity × Volume × Molar mass.
Example calculation
Prepare 2 L of 0.5 M NaOH solution. Molar mass NaOH = 40 g/mol. Mass = 0.5 × 2 × 40 = 40 g. Dissolve 40 g NaOH in water, make up to 2 L.
Engineering notes
Always add acid to water (not water to acid) when preparing acidic solutions. Use volumetric flasks for accurate concentration. For concentrated acid dilutions, calculate heat of dilution and cool the solution. Verify concentration of critical solutions by titration or pH measurement.
When to use this calculator
- Chemical dosing — calculate reagent concentration and dose volume for water or effluent treatment
- Laboratory preparation — prepare standard solutions of known concentration for analysis
- Cleaning solution preparation — calculate chemical concentrate required for specified use-strength
- Corrosion inhibitor dosing — determine inhibitor quantity for process water treatment
- pH adjustment — calculate acid or alkali dose to achieve target pH in a process tank
Frequently asked questions
- What is molarity and how is it different from molality?
- Molarity (M) = moles of solute per litre of solution. It is the most common concentration unit in chemistry and changes with temperature (because liquid volume changes). Molality (m) = moles of solute per kilogram of solvent. It does not change with temperature, making it preferable for thermodynamic calculations. For most laboratory and industrial applications at near-ambient temperature, molarity is used.
- How do I dilute a concentrated solution to a target molarity?
- Use the dilution equation: C₁V₁ = C₂V₂, where C₁ and V₁ are the concentration and volume of the stock solution, C₂ and V₂ are the target concentration and volume. Example: dilute 11.6 M HCl to 1 M, prepare 500 mL: V₁ = (1 × 0.5) / 11.6 = 0.043 L = 43 mL. Carefully add 43 mL concentrated HCl to approximately 400 mL water, then make up to 500 mL.
- What safety precautions apply when preparing chemical solutions?
- Always wear PPE: chemical-resistant gloves, safety goggles, lab coat. Work in a fume hood for volatile chemicals. Add acid to water — NEVER water to concentrated acid (exothermic, can splatter). Check SDS (Safety Data Sheet) for each chemical before preparation. Have eyewash station and emergency shower accessible. Label all prepared solutions clearly with name, concentration, date, and hazard pictograms.