Remember?

Q1: What can dissolve gold?
Q2. What is the medical application of platinum?
Q3: What is 砒霜?

A1: Aqua regia (also known as royal water or 王水 ) can dissolve gold. Aqua regia is prepared by mixing one part of concentrated nitric acid with three parts of concentrated hydrocholric acid. It is interesting to note that neither concentrated nitric acid nor concentrated hydrocholric acid alone can dissolve gold.

A2: cis-platin, [PtCl2(NH3)2], is an effective drug for certain types of cancer.

A3: Arsenic, another Group 5 element.