Popular LabKit · Recipe
0.1 N Hydrochloric Acid: Preparation and Standardisation
How to prepare 0.1 N (0.1 M) HCl from 37% hydrochloric acid and standardise it with anhydrous sodium carbonate – quantities, method, formula and a worked example.
Preparation: 0.1 N (0.1 M) hydrochloric acid, 1000 mL
| Component | Amount |
|---|---|
| Hydrochloric acid 37% (about 12 M) | 8.5 mL (8.3 mL theoretical) |
| Purified water | to 1000 mL |
Preparation
- Work in a fume hood with gloves and eye protection.
- Put about 500 mL of purified water in a 1000 mL volumetric flask.
- Add 8.5 mL of concentrated hydrochloric acid slowly, using a measuring cylinder or pipette. Always add acid to water.
- Mix, cool to room temperature and make up to 1000 mL.
Standardisation with sodium carbonate
- Dry anhydrous sodium carbonate at 270 °C for 1 hour and cool in a desiccator.
- Weigh accurately about 0.15 g into a conical flask and dissolve in 50 mL of water.
- Add 2 drops of methyl orange (or methyl red) indicator.
- Titrate with the HCl until the colour changes. With methyl red, boil gently for 2 minutes near the end point to expel CO₂, cool and finish the titration.
- Repeat twice more and use the mean factor.
1 mL of 0.1 M HCl ≡ 0.005300 g Na₂CO₃
Worked example
0.1520 g Na₂CO₃ needed 28.45 mL. Molarity = 0.1520 ÷ 105.99 × 2 ÷ 0.02845 = 0.1008 M, factor 1.0082.
Calculate your factor (pre-filled) →
Recipes are calculated with the Popular LabKit buffer model (ionic strength and temperature corrected) and checked against published buffer tables. For a pharmacopoeial test, follow the reagent or buffer recipe in your monograph. Always confirm pH with a calibrated pH meter.
Frequently asked questions
Why use 8.5 mL instead of 8.3 mL?
Concentrated HCl loses HCl gas over time and bottle strengths vary (35–38%). Taking slightly more gives a solution just above 0.1 N, and standardisation gives the exact factor.
Can I standardise HCl with borax?
Yes – borax (sodium tetraborate decahydrate) is also a primary standard for acids. Choose “Hydrochloric acid vs borax” in the factor calculator.
Is 0.1 N HCl the same as 0.1 M?
Yes, because HCl gives one H⁺ (n-factor 1). For sulphuric acid, 0.1 N = 0.05 M.