Hello, I did an experiment to try and clean copper pennies with acids like lemon juice and vinegar. When they are dipped in only lemon juice, nothing happens. However, when you add salt, the effect is almost instantaneous. Why does adding salt to lemon juice (citric acid?) make it a much stronger acid? I've looked online and some people say it is because you have H+ and Cl- which makes hydrochloric acid but it also says that it is not the real explanation. If someone can explain what is really going on, that would be great.