Easy
Chemical formula of rust is -
Explanation
Explanation
Rust forms when iron reacts with oxygen and moisture in the air, producing hydrated iron(III) oxide, whose basic chemical formula is written as Fe2O3. 'Fe' alone is just plain iron metal, not rust. So the correct answer is Fe2O3, option (1).
PRO TIP
Re-check your working by substituting the answer back into the original question.