Question

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

Answer 1

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

Explanation:

`38%` `HCl` 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 `"1 part acid"` to `"3 parts"` water by volume. The order of addition is IMPORTANT.

Answer 2

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 % `"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

`color(blue)(bar(ul(|color(white)(a/a) c_1V_1 = c_2V_2color(white)(a/a)|)))" "`

We can rearrange this formula to get

`V_1 = V_2 × c_2/c_1`

In your problem,

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

∴ `V_1 = "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.