Volume or percentage strength of hydrogen peroxide is a term to express concentration of H2O2 in terms of volumes of oxygen gas based on its decomposition to form water and oxygen. 2H2O2 →Δ 2 H2O + O2 The volume of oxygen released at S.T.P. is used to quantitate the concentration of hydrogen peroxide in solution and this is called the volume strength or percentage strength. Volume strength is the volume of oxygen at STP liberated from one volume sample of hydrogen peroxide on heating. 1 volume of H2O2 gives 20 volume of O2 at S.T.P Conversion of molarity to volume strength Suppose we have a solution of M moles of H2O2 in 1L solution From the reaction stoichiometry, 2 moles of H2O2 gives 1mol of oxygen or 22.4L at S.T.P 1mole of H2O2 = 11.2 L of O2 M mole of H2O2 = 11.2 x M L of O2 1L of H2O2 gives 11.2 x M L of O2 Vol strength of H2O2 = 11.2 x M In terms of Normality, N n factor for H2O2 is 2 N = M x n or N = M x 2 Volume strength = 11.2 M = 11.2 x N/2 = 5.6 N
