Question

The 20-ml volume of water added to the erlenmeyer flask is to be previously boiled, deionized water. since water does absorb co2 from the atmosphere and since co2 dissolved in water causes it to be slightly acidic, will the use of deionized water that has not been previously boiled cause the mass of acetic acid in the vinegar to be calculated as too high or too low? explain.

Answer 1

The amount of acetic acid in vinegar is determined by the volumetric titration of acetic acid with standardized NaOH solution. When atmospheric carbon dioxide is absorbed by deionized water used in the titration, it would react with water and form carbonic acid.

$CO_{2}(aq) + H_{2}O(l) H_{2}CO_{3}(aq)$

When the deionized water is contaminated with carbonic acid, it would result in the consumption of a higher amount of NaOH for neutralization. Therefore, the amount of acetic acid determined would be too high than it should be.