Question

Why do we boil water first, in the vinager analysis lab?

Answer 1

Ans. Distilled water stored in carboy or other vessels turn acidic due to solvation of some CO₂ gas in it.

            H₂O + CO₂ -----> H₂CO₃ ------> H⁺ + HCO₃^-

CO₂ reacts with water to form carbonic acid. Carbonic acid is a weak acid that dissociates to form H⁺ ions in water, thus makes it acidic.

# If some CO₂ is already there is the distilled water (to be used to dissolve vinegar), the total acidity of resultant vinegar is greater than the actual as follow-

            Total acidity = acidity due to vinegar + acidity due to CO₂

So, if such solution is analyzed for vinegar, the resultant amount of vinegar would be greater than actual because NaOH neutralizes both the vinegar and carbonic acid.

# Boiling water removes dissolved CO₂ from water. Preparing vinegar solution/dilution in boiled water eliminates the chances of error due to contamination carbonic acid.

Therefore, boiling the water before vinegar analysis is preferred.