# Question #93cfa

Sep 26, 2016

You need to know the concentration accurately to work out the molarity of the concentrated acid.......

#### Explanation:

Concentrated hydrochloric acid is available in a variety of concentrations that are all in the reagion of 37 - 39% HCl, so you would need to know the exact % of your starting material before making your 1M acid.

If you take the product supplied by Sigma Aldrich for lab use, that is stated as being 37.2% or 12.1M solution.

To make the 1M solution you simply mix some of the concentrated acid into water using an appropriate volumetric container.

To work out how much acid you need, just use:

${M}_{1} / {M}_{2}$ x V where ${M}_{1}$ is your desired molarity, ${M}_{2}$ is the current molarity, and V is the volume you want in ml.

Lets say you want 1000 ml of 1M hydrochloric acid.

$\frac{1}{12.1}$ x 1000 = 82.6

So you carefully measure out 82.6 ml of 37% hydrochloric acid into your volumetric container using a syringe or other suitable device (or work out the mass from the density and use a 4 place balance) then make up the volume to 1000 ml with water. Mix thoroughly - all done!