Chemistry Titration

Question

In a titration of 72.0 mL of a 0.500 M solution of a diprotic acid H₂C₃H₂O₄ (malonic acid) with 0.255 M NaOH, how many mL of the base are required to reach the first equivalence point?

Answer 1

Write the correctly balanced equation to reach the FIRST equivalence point:

H₂C₃H₂O₄ + NaOH ==> HC₃H₂O₄Na + H₂O .. balanced eq for first equivalence point

Moles H₂C₃H₂O₄ = 72.0 ml x 1 L / 1000 ml x 0.500 mol / L = 0.0360 mol H₂C₃H₂O₄

Moles NaOH required = 0.0360 mol H₂C₃H₂O₄ x 1 mol NaOH/mol H₂C₃H₂O₄ = 0.0360 mol NaOH

Volume NaOH needed = 0.0360 mol NaOH x 1 L / 0.255 mol x 1000 ml / L = 141 ml NaOH needed