The process may be natural during time.
No. The citric acid in the tomatoes changed the copper oxide back to copper.
If the coin is a valuable coin you shouldn't use anything acid or cleaner on it you will devalue the coin
if pH paper is dipped in a strong acid it turns red and if the same pH paper is dipped in the weak acid it turns blue
Copper+Nitric Acid - Copper Nitrate
Only if the acid is above the melting point of copper. However, the copper might dissolve in acid if the acid is oxidizing. If it did, copper ions would be present in the solution formed, but there would not be an metallic copper in it.
Sulfuric acid plus copper (II) nitrate yields nitric acid plus copper (II) sulfate. Sulfuric acid plus copper (I) nitrate yields nitrous acid plus copper (I) sulfate.
No. Copper oxide has no acid-base properties.
Copper dissolves in any oxidising acid like nitric acid.
16Mtric acid will dissolve copper, without heating.
No, Copper is a metal.
Turns red.
no