Calculation of molarity of 30% H_{2}O_{2} solution


1. Overview
H_{2}O_{2} 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). H_{2}O_{2} is commercially available as 30%  40% (weight / weight) aqueous solution. Most of our biological experiments use molar concentration of H_{2}O_{2}, 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 H_{2}O_{2} solution
If one carefully read the bottle of H_{2}O_{2} or Data sheet, one may find the concentration of H_{2}O_{2} written like this:
30% H_{2}O_{2} by weight
30% H_{2}O_{2} Weight / Weight
This means 30 g of H_{2}O_{2} is present in 100 g of solution (See 2.1).
4. Result
The Molarity of 30% H_{2}O_{2} (Weight / Weight) solution (Or 33.30 % H_{2}O_{2} solution (Weight / Volume) is 9.79.