The Percent Purity of a Malonic Acid Reagent Must Be

The percent purity of a malonic acid reagent must be calculated.A student weighs out 0.1511 grams of malonic acid,CH₂(CO₂H)₂,and quantitatively transfers the solid to a 250 mL Erlenmeyer flask.To the flask 50.00 mL of distilled water is added to dissolve the malonic acid.After dissolution,the student uses a 50 mL volumetric pipet to add 50 mL of 0.200 M Ce⁴⁺,which is allowed to react with the malonic acid.After complete reaction,the excess Ce⁴⁺ is back titrated with 14.58 mL of 0.100 M Fe²⁺ solution.Calculate the percent purity malonic acid.
CH₂(CO₂H)₂ + 2 H₂O + 6 Ce⁴⁺ → 2 CO₂ + HCO₂H + 6 Ce³⁺ + 6 H⁺
Ce⁴⁺ + Fe²⁺ ⇋ Ce³⁺ + Fe³⁺