In chemistry we did a lab examining iron nails corroding in agar. one of the nails was wrapped in zinc, and the nail did not rust. a whitish substance appeared around the nail, what is the whitish substance?

Zn(OH)₂

Explanation:

Zn is above Fe in the activity series, so it is more readily oxidized:

Zn(s) ⟶ Zn²⁺(aq) + 2e⁻

The zinc ions go into solution.

The electrons travel from the Zn to the surface of the iron nail, where they reduce the water to hydrogen and hydroxide ions.

2H₂O(ℓ) + 2e⁻ ⟶ H₂(g) + 2OH⁻(aq)

Neither the zinc ions nor the hydroxide ions can move far through the gel.

Their concentration builds up around the hail. The ions find each other and form a precipitate.

Zn²⁺(aq) + 2OH⁻(aq) ⟶  Zn(OH)₂(s)