Question

Oxalic acid is often used to remove rust stains. What properties of oxalic acid allow it to do this?

Short answer

Oxalic acid is widely used in the form of acid rinse in laundriesbecause of its effective nature in removing rust and ink stains.

Rust consists of iron. Oxalic acid helps inconverting most of the insoluble iron compounds into some soluble complex ions.

Step-by-step solution

Oxalic Acid.

The formula of oxalic acid is$H_2{C}_2{O}_4$ . The acidic nature is because it can release its H-atoms in the aqueous solution when dissolved.

The RUST.

Rust (iron oxide) contains iron. It has a formula${\text{Fe}}_{\text{2}}{\text{O}}_{\text{3}}$ .

When oxalic acid is used, it forms a soluble oxalate complex with the iron (III) ion, which is present in the rust.

$H_2{C}_2{O}_4+F{e}_2{O}_3\to Fe{C}_2{O}_4$

The iron that is formed has a +2 oxidation state and therefore is called Iron(II) Oxalate.

The Properties of Oxalic Acid

The bleach-like nature of oxalic acid helps remove rust from the strained body.

Many cleansing products, like detergents, contain oxalic acid.

The acid is also used in polishing several old objects.