calculate the molar concentration of the malonic acid if 38.17 mL of 0.315 M potassium hydroxide was required to neutralize 25.0 mL of malonic acid to a phenolpthalein end point.

Question

not sure how to proceed after determining the moles ;/

Answer 1

Hello Jasmine

The balanced equation for this neutralization reaction is:

HOOC-CH2-COOH + 2KOH --> K^+ -^OOC-CH2-COO^- K^+ + 2H2O

Malonic acid is a dicarboxylic acid, which requires 2 moles of KOH to neutralize 1 mole of malonic acid. Use the volume and Molarity of KOH to calculate the moles of KOH used.

moles of KOH = 0.315 mol/L x 38.17 mL x (1 L / 1000 mL) = 0.0120 mol KOH

moles of malonic acid (MA) neutralized = 0.0120 mol KOH x (1 mol MA / 2 mol KOH) = 0.00600 mol MA

Volumes in a titration are additive. Total volume of the solution after neutralization = Vacid + Vbase = 25.0 mL + 38.17 mL = 63.17 mL

Molarity of MA = (0.00600 mol / 63.17 mL) x (1000 mL / 1 L) = 0.0950 M