Aqua Regia dissolves Gold - Periodic Table of Videos
Why Chemistry Stack Exchange recommends it
Chemistry Stack Exchange users link it when they need a clear demonstration of aqua regia dissolving gold, whether as an illustration in an answer or as a cited explanation in a question.
Recommended by 1 people across 1 different months, 2016 to 2020.
What it is
A short Periodic Videos demonstration in which a piece of gold is dissolved in aqua regia, a mixture of nitric and hydrochloric acids. Professor Martyn Poliakoff of the University of Nottingham explains the chemistry while Brady Haran films, as the first of the channel's extra "Molecular Videos".
What people said
Recommends Jacob Nowatzke · 2016-09 · Chemistry Stack Exchange · on “Are there metals that react with sulfuric acid but not hydrochloric (or vice versa)?”
I think you will be astounded to learn about aqua regia [this video] . Also, have a look at the reactivity series [LINK] to learn more about the reactivity of various metals. To make your point that different metals react differently, you could reference this reactivity series and show the trend of certain metals and their ions to lose and/or gain electrons. Following on what @Hanry said, in aqua regia, nitric acid is used to partially dissolve the gold, whereas hydrochloric acid is used to "take advantage" of chloride ions by using them to form a complex with chloride anions to form a complex of tetrachloroaurate(III) anions, thereby allowing nitric acid to continuously dissolve a small amount o
Cites Spencer · 2019-01 · Chemistry Stack Exchange · on “Why does the surface of an acid appear to have a stronger "dissolving power"?”
In this Periodic Videos YouTube video [this video] by Brady Haran and the University of Nottingham, we see a piece of gold being dissolved in aqua regia [LINK] , while Professor Poliakoff explains why aqua regia can dissolve gold even though its constituent acids can't. The piece of gold was placed partway into the acid. I noticed that the acid appears to attack the gold the strongest at the liquid's surface, and the gold was first "dissolved through" along a line at the surface, leaving a little plate of undissolved gold dangling in the acid by one corner. You can see this best from about 4:10 to 4:30 into the video. I was wondering if there's some effect at the surface of the liquid that causes
Cites KingLogic · 2020-05 · Chemistry Stack Exchange · on “Can aqua regia/royal water be produced with sources of chloride and nitrate other than hydrochloric acid and nitric acid?”
According to Professor Poliakov [this video] and a question on Chemistry Stackexchange [LINK] here, gold dissolves in aqua regia because the nitrate ion oxidizes the gold into $\ce{Au^3+}$ , and the chloride bonds to the gold to form tetrachloroaurate III ions ( $\ce{AuCl4−}$ ). This means that the actual acidity of the compound plays no role in the actual oxidization and dissolution of gold. Therefore, if I just provide nitrate ions and chloride ions, the reaction should still proceed (ex: use $\ce{NaNO_3}$ for the source of nitrate ions and $\ce{NaCl}$ for the source of chloride ions). According to the equations given by an answer to the Stackexchange question earlier [LINK] , aqua regia can re