Question

If oxygen is removed from a sample of air as iron rusts, what happens to the partial pressure of oxygen in the air?

Answer 1

It increases

Explanation:

There are 2 key things to know

1, Rusting is where oxygen binds to iron and forms iron oxide.
So once iron rusts, there is oxygen, just not in air; it's in the iron oxide.

1. All reactions are reversible, albeit at different rates (the "irreversible" ones are still reversible, but much slower given that they take so much collision luck and energy.

So given this, if you take away all of the oxygen in the air, the partial pressure is 0 atm. And the only thing iron oxide can do is decompose, then the pressure will only go up (very slightly though.)
(0.000000000001atm is greater than 0atm)