Oxalic acid solution titrated with NaOH solution using phenolphthalein as an indicator.H2​C2​O4​+2NaOH⟶Na2​C2​O4​+2H2​OEquivalent of H2​C2​O4​ reacted = Equivalent of NaOH reactedM(NaOH)​​=10005×2×0.1​=10009×M(NaOH)​×1​=91​=0.11​