1. The problem statement, all variables and given/known data Basically I'm doing a lab report where we place copper pennies in a solution of salt and vinegar. This should strip the copper oxide off the outside of the pennies, leaving the copper underneath shiny and looking "new". The problem is why we add the salt. 2. Relevant equations The main reaction is with the copper oxide and the vinegar. 2 C2H4O2 + Cu ===> Cu(C2H3O2)2 + H2 3. The attempt at a solution I've looked online and I see some people's opinions are that the salt was added so the chlorine in it would combine with some hydrogen to form hydrochloric acid, however, wouldn't the bonds between NaCl be too strong for this to happen in an acid like vinegar? My guess is that salt somehow speeds this up because it is corrosive to metals?