OVERVIEW

A 70% (w/w) perchloric acid can be purchased from several commercial suppliers. It is a clear colorless liquid and can be diluted to prepare solutions of known concentrations. Here we describe a procedure to prepare 1M perchloric acid solution by diluting a 70% (w/w) concentrated perchloric acid solution.

REQUIREMENTS

Reagents and solutions
70% (w/w) perchloric acid stock solution
Distilled water

Equipment and disposables
Measuring cylinder/volumetric flask
Beaker (1 Liter)
Magnetic stirrer

OBJECTIVE
Preparation of 1 Liter of 1M perchloric acid solution using Concentrated Stock Solution (70%, w/w)

PROCEDURE

Use personal protective equipment (lab coat, gloves, goggles etc) for your safety and follow the guidelines of your institute.

PART I: Calculate how much 70% (w/w) concentrated perchloric acid stock solution is required to prepare 1 L of 1 M perchloric acid solution

Step 1: Calculate the molarity of 70% (w/w) concentrated perchloric acid solution
The procedure to calculate molarity of 70% (w/w) concentrated perchloric acid solution is described in detail in the post “Molarity of 70% (w/w) Perchloric Acid (HClO4)”. From this post, you will know that the molarity of 70% (w/w) concentrated perchloric acid solution is 11.706M.

Step 2: Calculate how much stock solution is required to prepare 1L of 1M perchloric acid solution using dilution method.

Dilution method is described in detail in the post “Preparing Working Solution from Stock Solution by Dilution”.

Use the following formula to calculate the volume of concentrated solution required for the preparation of 1 liter of 1M solution of hydrochloric acid solution

Formula:   C_f x V_f = C_S x V_S

C_f (concentration of diluted (final) solution) = 1M
V_f (volume of diluted (final) solution) = 1 liter
C_S (concentration of stock solution) = 11.706 M
V_S (volume of stock solution) = ? (unknown)

Place all values in the formula:

1 x 1 = 11.706 x V_S

V_S = 1x 1/ 11.706 = 0.08542 liter (85.42 ml)

So you need 0.08542 liter (85.42 ml) liters of 70% (w/w) concentrated perchloric acid solution to prepare a 1 liter of 1M perchloric acid solution.

Step 3: Calculate the volume of solvent to be taken.

Final volume of diluted solution = 1 liter
Volume of concentrated solution = 0.08542 liter
Volume of solvent (water) required = 1 – 0.08542 = 0.91458 liter

So you need to mix 0.08542 liter (85.42 ml) of concentrated solution to 0.91458 liter (914.58 ml) water to prepare 1 liter of 1M perchloric acid solution.

STORAGE
Solution can be stored at room temperature.