What is the actual formula for iron rust ??
Rust is just iron oxide, so it is made up of iron and oxygen. We can find the empirical formula (simplest ratio of a compound's components) by looking at the ions each element forms.
Compounds have an overall neutral charge, so we need to find a combination of iron and oxygen which results in their charges balancing out. This basically involves finding the lowest common multiple of their two charges - so for 2 and 3 this is 6, and so we have
This gives us the final formula
Hope this helped; let me know if I can do anything else:)