IUBio Biosequences .. Software .. Molbio soft .. Network News .. FTP

How to prepare 1M H2O2 using 30% hydrogen peroxide?

thekingmbembe from gmail.com via methods%40net.bio.net (by thekingmbembe from gmail.com)
Thu Sep 27 05:15:19 EST 2018

c(H2O2) = 1 mol/L
To prepare 100 mL of a 1 mol/L solution of hydrogen peroxide we will need to dilute 5.68513 mL of 50 % H2O2 to a final volume of 100 mL with deionized (distilled) water.

    Name: Hydrogen peroxide  
    Formula: H2O2
    Formula weight: 34.015 g/mol
    CAS Number: 7722-84-1 
    NFPA: Health 3, Flammability 0, Instability 1, Special OX

The key concept is that the amount of solute in the desired solution must be equal to the amount of solute in the source solution. Remember, the concentration is the amount of a solute divided by the volume of the solution.

Before we make any calculations we have to make sure that we only use one system and one unit of measurement. DO NOT mix measurement systems and units.

    Desired solution:
    V0 = 100 mL * (1 L)/(1000 mL) = 0.1 L
    c0 = 1 mol/L
    Source solutions:
    w1 = 50 % = 50 * 1/100 = 0.5
    d1 = 1.19662 kg/L * (1 g/L)/(0.001 kg/L) = 1196.62 g/L

Then, we determine the concentration of the source (stock) solution

    c1 = d(H2O2) * w(H2O2) / M(H2O2)
    c1 = 1196.62 g/L * 0.5 / 34.0147 g/mol
    c1 = 17.5897 mol/L

Since the total amount of solute is the same before and after dilution, the volume of stock solution needed is

    V1 = V0 * c0 / c1
    V1 = 0.1 L * 1 mol/L / 17.5897 mol/L
    V1 = 0.00568513 L

To convert the result into a desired unit we will use dimensional analysis again

    V(50 % H2O2) = 0.00568513 L * (1000 mL)/(1 L) = 5.68513 mL

First of all, fill the volumetric flask about halfway with deionized water to avoid violent reactions. NEVER add water to concentrated acid.

Choose a clean pipette of suitable size and transfer the liquid to the volumetric flask. When the whole solution has been drained, touch the tip of the pipette to the side of the volumetric flask to allow the last of the liquid to drain out. DO NOT blow out the remaining solution.

Allow the solution to reach room temperature because a volumetric flask is only accurate at the temperature at which it has been calibrated (usually 20 癈). Very carefully fill the flask to the mark on the neck of the flask, using a dropping pipette to add the last few milliliters of liquid. Mix your solution thoroughly, by inverting the flask and shaking. NEVER hold large volumetric flasks by the neck alone - provide support at the bottom.

Transfer the prepared solution to a clean, dry storage bottle and label it. NEVER store solutions in a volumetric flask.

- When making chemical solutions, always use the appropriate safety equipment.
- As a general rule, always add the more concentrated solution to the less concentrated solution.
- All chemicals that you are unfamiliar with should be treated with extreme care and assumed to be highly flammable and toxic.

More information about the Methods mailing list

Send comments to us at biosci-help [At] net.bio.net