molarium
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Acid & base stocks

% w/w

From the bottle label or certificate.

g/mL
g/mol

Stock as supplied

Molarity 11.97 M
Content 436.6 g/L

To prepare the dilution

Concentrated stock 83.51 mL
Water 916.5 mL

Always add the concentrated acid or base slowly to water, never water to acid. Work in a fume hood.

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Method & reference

Molarity of a concentrated reagent from its assay and density, and the volume to dilute.

M = (% ÷ 100) × ρ (g/mL) × 1000 ÷ MW. Then Vstock = Mtarget × Vtarget ÷ Mstock. Typical assay and density values are pre-filled; replace them with the values on your bottle. Always add acid to water.

What is the molarity of concentrated hydrochloric acid?

Concentrated HCl is about 37 % w/w with a density of 1.18 g/mL, which is 0.37 × 1.18 × 1000 ÷ 36.46 = 11.97 M, usually rounded to 12 M. Check the exact assay on your bottle.

How do I make 1 L of 1 M HCl from concentrated acid?

Take 1 ÷ 11.97 L = 83.5 mL of concentrated acid and add it slowly to about 900 mL of water, then make up to 1 L. Always add acid to water, never water to acid.

Why is ammonium hydroxide given on an NH3 basis?

Ammonia solution is sold as 25 to 30 % NH3 by weight, so its molarity is calculated with the molar mass of NH3, 17.03 g/mol, giving about 14.8 M for a 28 % solution.