Concentrated Acid Molarity and Dilution Calculator
Concentrated Acid Molarity and Dilution Calculator
Calculate the molarity of 37% HCl, 98% H2SO4, 65% HNO3 and other concentrated reagents from their assay and density, then how many mL to pipette to make a dilute solution.
What is the molarity of a concentrated reagent?
Concentrated acid labels do not state molarity. They state the assay (% w/w, mass percent) and the density. You need to calculate the molarity first before diluting it with the dilution formula M1 × V1 = M2 × V2.
Concentrated acid molarity formula
The factor 10 comes from the unit conversion: 1 L of solution with density ρ g/mL weighs 1000 × ρ grams, and % of that mass is solute (1000 × ρ × % ÷ 100 = 10 × % × ρ grams per litre).
Molarity of common concentrated reagents
| Reagent | Assay | Density (g/mL) | Mr | Molarity | Normality |
|---|---|---|---|---|---|
| HCl | 37% | 1.19 | 36.46 | 12.08 M | 12.08 N |
| H2SO4 | 98% | 1.84 | 98.08 | 18.38 M | 36.77 N |
| HNO3 | 65% | 1.40 | 63.01 | 14.44 M | 14.44 N |
| CH3COOH | 100% | 1.05 | 60.05 | 17.49 M | 17.49 N |
| NH3 | 25% | 0.91 | 17.03 | 13.36 M | 13.36 N |
| H3PO4 | 85% | 1.69 | 97.99 | 14.66 M | 43.98 N |
| H2O2 | 30% | 1.11 | 34.01 | 9.79 M | – |
Assay and density values above are typical. The actual assay is on the label and lot CoA, and density shifts slightly with temperature, so use the values from your bottle for an exact result. H3PO4 normality assumes full neutralisation (e = 3).
Worked examples
Example 1: 0.1 M HCl from 37% HCl
How many mL of 37% HCl (ρ 1.19 g/mL) are needed for 1000 mL of 0.1 M HCl?
- M1 = 10 × 37 × 1.19 ÷ 36.46 = 12.08 M
- V1 = M2 × V2 ÷ M1 = 0.1 × 1000 ÷ 12.08 = 8.28 mL
Answer: pipette about 8.3 mL of 37% HCl into a 1000 mL volumetric flask that already contains water, then make up to the mark.
Example 2: 1 N H2SO4 from 98% H2SO4
How many mL of 98% H2SO4 (ρ 1.84 g/mL) are needed for 500 mL of 1 N H2SO4?
- H2SO4 releases 2 H+, so 1 N = 0.5 M
- M1 = 10 × 98 × 1.84 ÷ 98.08 = 18.38 M
- V1 = 0.5 × 500 ÷ 18.38 = 13.60 mL
Answer: about 13.6 mL of 98% H2SO4, added slowly to water with stirring and cooling.
Safety when diluting concentrated acids
- Acid into water, never water into acid. Diluting H2SO4 releases a lot of heat; water poured into concentrated acid can boil instantly and spatter.
- Work in a fume hood with safety glasses, acid-resistant gloves and a lab coat.
- Add the acid in small portions while stirring, and let the solution cool before making up to the mark.
- Know the hazard pictograms on our hazard symbols page and read your reagent's SDS.
FAQ
What is the molarity of 37% HCl?
At a density of 1.19 g/mL, 37% HCl is about 12.08 M (also 12.08 N, since e = 1).
What is the molarity of concentrated H2SO4?
98% H2SO4 at 1.84 g/mL is about 18.38 M, or 36.77 N.
Why is my result slightly different from other tables?
Sources use slightly different assay and density values (for example 36% or 37% HCl, density 1.18 or 1.19). A few percent difference is normal; use the values on your bottle.
Does the diluted solution need standardisation?
For titration, yes. The assay of a concentrated reagent is not precise enough for a standard solution, so diluted HCl or H2SO4 is standardised against a primary standard such as sodium carbonate or borax. See the titration formula.
Prepare solutions with analytical-grade reagents
AMI Scientific is one of the official TCI distributors in Indonesia. Reagents with lot CoA & SDS, formal quotations and tax invoices for universities and laboratories.
Other formulas & calculators: molarity, mole, molality, normality, dilution, titration, pH, buffer, molar mass, ppm, mole fraction, mass percent, periodic table, chemical MSDS.