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How do we dilute concentrated hydrochloric acid to give 10% HCl?

Mar 2, 2017

Carefully, and YOU ALWAYS ADD ACID TO WATER..........You also wear a lab coat and a pair of safety spex..................

Explanation:

38% $H C l$ is as far as I know the most concentrated hydrochloric acid solution you can get.

The reported concentrations must be: "mass of HCl"/"mass of solution"xx100%.

And thus you add $\text{1 part acid}$ to $\text{3 parts}$ water by volume. The order of addition is IMPORTANT.

Mar 21, 2017

You add 260 mL of the 38 % acid to enough water to make 1 L.

Explanation:

Let's say you wanted to prepare 1 L of 10 % $\text{HCl}$.

Since you are using solutions with the same concentration units, you don’t need the density information.

You can simply use the dilution formula

$\textcolor{b l u e}{\overline{\underline{| \textcolor{w h i t e}{\frac{a}{a}} {c}_{1} {V}_{1} = {c}_{2} {V}_{2} \textcolor{w h i t e}{\frac{a}{a}} |}}} \text{ }$

We can rearrange this formula to get

V_1 = V_2 × c_2/c_1

c_1 = 38 %; V_1 = ?
c_2 = 10 %; V_2 = "1 L"

${V}_{1} = \text{1 L" × (10 color(red)(cancel(color(black)(%))))/(38 color(red)(cancel(color(black)(%)))) = "0.26 L" = "260 mL}$

Thus, you would slowly and carefully add 260 mL of the 38 % acid to about 500 mL of distilled water in a volumetric flask, always swirling gently to make sure that the acid is evenly mixed.

Then you would add more distilled water until the level just reaches the 1 L mark on the flask.

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