Ethanoic (Acetic) acid and NaOH Reaction, pH change, Titration
Aqueous ethanoic (acetic) acid is a carboxylic acid. Rection of ethanoic acid and aqueous NaOH is a weak acid - strong base reaction. Sodium ethanoate (salt) and water are given as products. During the titration of acetic acid and NaOH, pH value is changed. Also, this reaction is an example to weak acid - strong base neutralization reaction.
written by: Heshan Nipuna, last update: 27/05/2020
CH3COOH + NaOH → CH3COO-Na+ + H2O
This reaction is an exothermic reaction (heat is given to outside).
Ethanoic acid and NaOH
Sodium ethanoate and water are given as products by the reaction of ethanoic acid and aqueous NaOH. Sodium ethanoate is a salt and soluble in water. pH of the solution is changed during the reaction.
Titration of adding sodium hydroxide to ethanoic acid
Aqueous ethanoic acid shows a pH value below than 7 (usually 3-7, but may change due to concentration). When, aqueous NaOH solution is added, ethanoic acid concentration is reduced and pH value is increased. When all ethanoic acid is finished (when reaction is completed), pH value will be just above than 7 because, sodium ethanoate is a weak base.
After completion of the reaction, if you add one more drop of NaOH, pH value increased dramatically due to presence free OH- in the solution given by NaOH.
Titration of adding ethanoic acid to aqueous sodium hydroxide
Aqueous sodium hydroxide shows a pH value higher than 7 because it is a strong base. When, aqueous ethanoic acid solution is added, NaOH concentration is reduced and pH value is decreased. When all NaOH is finished (when reaction is completed), pH value will be above than 7 because, sodium ethanoate is a weak base as when sodium hydroxide is added to ethanoic acid.
Heat of reaction
- Heat of reaction: -56.1 kJ mol-1
When 1 mol of aqueous NaOH reacts with 1 mol of ethanoic acid, 56.1 kJ is emitted to the outside. This energy is less than strong acid - strong base neutralization enthalpy.
Questions asked by students
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If same amount (mol) of sodium hydroxide and ethanoic acid are mixed, what will be the pH value, is it less than seven or greater than seven?
When same amount (mol) of sodium hydroxide and ethanoic acid are mixed, mixture contains sodium ethanoate. Sodium ethanoate dissociate completely in the water to ethnaote ion and sodium ion. But, ethnaote ion is not stable in the water and hydrolysis the water and release hydroxyl ions. Due to formation of hydroxyl ions, solution become basic and pH value will be higher than seven.
Is ethanoic acid and sodium hydroxide reaction similar to the ethanoic acid and potassium hydroxide reaction
Yes. Both sodium hyroxide and potasium hydroxide are srong base reacts in same way with ethanoic acid
I have prepared sodium ethanoate from the reaction of ethanoic acid and sodium hydroxide. Can I get back ethanoic acid from sodium ethanoate?
You can try adding aqueous HCl to sodium ethanoate. Then you can do a separation method to get ethanoic acid.