1. During electroplating copper (for example), the impure copper is made the anode. After passing through electricity, some impurities such as gold, silver and platinum will settle at the bottom of the container. Why they don't like other metal ions, like zinc ions, oxidise themselves?
2. Chlorine gas is used to sterliise the water of swimming pool, but sodium hypochlorite (NaOCl) is more preferrable. Why?