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Oxalic Acid Formula – Structure, Properties, Uses, Sample Questions

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  • Last Updated : 01 Jun, 2022
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Carbon (C), is a non-metallic chemical element in group 14 of the periodic table. Although widely distributed in nature, carbon is not abundant enough to make up only about 0.025% of the Earth’s crust but forms more compounds than all other elements combined.

Hydrogen (H), a colorless, odorless, tasteless, flammable gaseous substance, is the simplest member of the chemical element family. A hydrogen atom has a nucleus made up of protons carrying a positive charge of one unit. Electrons are also associated with this nucleus, which carries one unit of negative charge. Under normal conditions, gaseous hydrogen is a loose accumulation of hydrogen molecules, each composed of a pair of atoms,  diatomic H2 molecules.

Oxygen is a chemical element with the symbol O and atomic number 8. It is a highly reactive nonmetal and oxidizing agent that readily forms oxides with most elements as well as other compounds.

What is the Oxalic acid formula?

It is a poisonous acid having a sour taste with the IUPAC name ethanedioic acid .it has the appearance of a white solid which forms a colorless solution in water. 

Oxalic acid is a strong dicarboxylic acid in nature and structure. Oxalic acid is a natural organic acid found in plants and vegetables. It is the simplest dicarboxylic acid containing only two carboxylic acids directly bonded to each other at carbon atoms, i.e. (COOH) groups. Hence, the formula of oxalic acid is C2H2O4.

Structure of Oxalic acid 

Oxalic acid crystallizes as columnar crystals with or without aluminum is a naturally occurring organic acid in plants, vegetables, etc. 


Preparation of Oxalic acid

Although readily available, oxalic acid can be made in the laboratory by oxidizing sucrose with nitric acid in the presence of a small amount of vanadium pentoxide as a catalyst. The hydrated solid can be dehydrated by heat or azeotropic distillation.


  • Take the watch glass, wash it with distilled water and let it dry.  
  • Weigh the exact amount of clean and dry watch glass and record its weight in a notebook. 
  • Correctly weigh 3.15 g of oxalic acid on a  watch glass and write down this weight in a notebook.  
  • Using a  funnel, gently and carefully transfer oxalic acid from the watch glass to a clean, dry volumetric flask. 
  • Wash the watch glass with distilled water and use a wash bottle to wash away the particles adhering to the watch glass with foam.
  • For completing the experiment, the amount of water should not exceed 50 ml.
  • Rinse the funnel with distilled water several times and use a wash bottle to flush the adherent particles into the volumetric flask.
  • Add a small amount of water while washing the funnel. 
  • The amount of distilled water used for this should not exceed 50 ml.
  • Rinse the funnel with distilled water and rinse the solution to funnel into a flask. 
  • Rotate the volumetric flask until the oxalic acid dissolves. 
  • Using a  wash bottle, fill the volumetric flask with sufficient distilled water just below the etched marks.
  • Add the last ml of distilled water droplets to the volumetric flask until the reduced meniscus level just touches the mark.
  • Place a stopper in the opening of the flask and shake gently to even out the entire solution. 
  • Now, we will get a solution of M/10 oxalic acid.

Physical Properties of Oxalic acid

  • The molar mass of oxalic acid is 126 g/mol. 
  • Its Density is 1.90 g/cm3
  • Its Melting points vary from 1890°C to 1910°C.
  • It appears as a white crystal and smells odorless.
  • Its heat capacity is 91.0 J·mol-1·K-1

Chemical Properties of Oxalic acid

  • For oxalic acid, the valence coefficient is 2. 
  • It readily reacts with typical carboxylic acids to form acid chlorides and ester derivatives. 
  • Oxalic acid is highly toxic and therefore harmful. Inhalation can cause serious damage to mucous membranes and the respiratory tract. Also, symptoms such as cough, and wheezing are one of the symptoms of this. It is also toxic if swallowed and can cause kidney failure.
  • When oxalic acid reacts with Potassium Manganate(VII), get dissociates as:

2MnO4– + 5C2H2O4 + 6H3O+   →   2Mn2+  +  10CO2 + 14H2O

  • The reaction of oxalic acid with concentrated sulphuric acid is given by,

 C2H2O4 + conc. H2SO4   →  CO + CO2 + H2O

Uses of oxalic acid 

  1. Oxalic acidencourages the dying process.
  2. As a strong acid, it is also useful as an extractor and reducing agent for lanthanide metals and as an analytical reagent.
  3. It can be used for polishing marble carvings and in bleach. 
  4. Oxalic acid is useful for removing food and ink stains. 
  5. Also useful for developing movies and used in wastewater treatment to remove calcium deposits.

Sample Questions

Question 1: Write the formula for oxalic acid and determine its basicity.


The formula for oxalic acid is (COOH)2.2H2O and its basicity is 2.

Question 2: How to convert oxalic acid solution M/20 to oxalic acid solution N/20?


To make the conversion, we have to add an equal volume of water so that the solution is converted to N/20.

Question 3: What happens when KMnO4 reacts with oxalic acid?


The reaction between oxalic acid and potassium permanganate is endothermic as a redox reaction that occurs in the presence of sulphuric acid and heat. Potassium permanganate and sulphuric acid produce oxygen, which reacts with oxalic acid to form carbon dioxide and water.

Question 4: Which indicator do you use to titrate KMnO4 with oxalic acid?


Potassium permanganate itself is purple and serves as its own indicator.

Question 5: Why do we heat oxalic acid solution containing sulphuric acid up to 50–60°C in the permanganate titration?


When heated to 50-60 °C, the oxalic acid remains decomposed, which contributes to a better interaction between oxalate and potassium permanganate.

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