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how to calculate the molarity of 30% hydrogen peroxide

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punu
India

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Status: Frog Egg
 Topic Started by punu on 12/26/2011 23:34 PM

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Robo
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Status: Frog Egg
 Posted By Robo on 1/17/2012 9:34 AM

Calculation of molarity of 30% H2O2 solution

1. Overview
H2O2 has been used in biological research as a source of ROS, as a inducer of apoptosis as well as in many protocols (APL enzyme reaction). H2O2 is commercially available as 30% - 40% (weight / weight) aqueous solution. Most of our biological experiments use molar concentration of H2O2, therefore, it is required to convert the % concentration to molar concentration.

2. List of important terms and formulars

• 2.1 Percent Concentration (Weight / Weight, also called by weight)
This can be defined as the amount of solute (in grams) present in 100 grams of solution. Following formula is used to calculate
Percent Concentration (Weight / Weight)= 100 X Amount of solute (in grams) / Amount of solution (in grams)
• 2.2 Percent Concentration (Weight / volume)
This can be defined as the amount of solute (in grams) present in 100 ml of solution. Following formula is used to calculate
Percent Concentration (Weight / volume)= 100 X Amount of solute (in grams) / Amount of solution (in ml)
• 2.3 Density
Density of a matter can be defined as the mass per unit volume. Following formula is used to calculate
Density = Mass / Volume
• 2.4 Mole
Mole of a substance can be calculated using following formula.
Moles = Mass of substance (in gram) / Atomic weight (Formula weight)
• 2.5 Molarity
Molarity can be defined as number of moles of solute present in 1 litre of solution. Molarity of a solution can be calculated using following formula.
Molarity = Number of moles of solute/ Volume of solution (in litre)

3. Calculation

• 3.1 Understanding the concentration terms of commercially available H2O2 solution
If one carefully read the bottle of H2O2 or Data sheet, one may find the concentration of H2O2 written like this:
30% H2O2 by weight
30% H2O2 Weight / Weight
This means 30 g of H2O2 is present in 100 g of solution (See 2.1).
• 3.2 Calculating the volume of 100 gram of H2O2 solution
If one carefully read the bottle of H2O2 or Data sheet, one may find the density of H2O2 solution. It is 1.11 g/ml.
Now calculate the volume of 100 gram of H2O2 solution using formula

Density = Weight / Volume (See 2.3)
Volume = Weight / Density

Density = 1.1 g/ml
Weight = 100 g
Volume = 100/1.1 = 90.09 ml

• 3.3 Calculating the percentage concentration (weight/volume) of H2O2 solution
Volume of solution = 90.09 ml
Amount of H2O2 = 30 gram

Formula
Percent Concentration (Weight / volume)= 100 X Amount of solute (in grams) / Amount of solution (in ml)
Percent Concentration (Weight / volume)= 100 X 30 / 90.09 = 33.30 gram H2O2 in 100 ml solution

• 3.4 Calculating the moles of H2O2 present in 33.30 gm of H2O2
Molecular weight of H2O2 = 34.01
Amount of H2O2 = 33.30 gram

Formula
Moles = Mass of substance (in gram) / Atomic weight (See 2.4)
Moles of H2O2 = 33.30 / 34.01 = 0.979 moles of H2O2
Now we know that 0.979 moles of H2O2 is present in 100 ml solution

• 3.5 Calculating the Molarity of H2O2 solution
Moles of H2O2 = 0.979
Volume of solution = 100 ml or 0.1 litre

Formula
Molarity = Number of moles of solute/ Volume of solution (in litre)
Moles of H2O2 = 0.979 / 0.1 = 9.79 M

4. Result
The Molarity of 30% H2O2 (Weight / Weight) solution (Or 33.30 % H2O2 solution (Weight / Volume) is 9.79.

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