Quantitative Analysis of Metallic Iron I put the penny in the silver nitrate solution for a half hour

Quantitative Analysis of Metallic Iron

I put the penny in the silver nitrate solution for a half hour. The penny gives black precipitation and bubbles which come off the surface of the penny.

My questions:
1. What is the gas that comes off the surface of the penny? (Hint: the half reactions that are going on between silver ions and copper)
2. Which is being reduced, the silver ions of the copper?
3. What would you expect to see (if anything) if instead of a penny, a piece of nickel metal was placed in a solution of zinc chloride?