A Cute Little Problem

Call it nostalgia, or call it slacking, but I was looking at some past CIC exams (part C) just now. And, ooh, cute problem!

Dilute hydrochloric acid was added to a metallic looking compound A (molecular weight 90.756). A colourless gas B with a characteristic, unpleasant odour was formed together with a pale green solution of the cation C.

The gas B was burned in air to give another colourless gas D that turned yellow dichromate paper green. Mixing B and D gave a yellow solid element E. Depending on the mole ratios, E reacted with chlorine gas to give two chlorides, F and G, in addition of hydrogen chloride (HCl).

Addition of zinc metal to a sample of the green cation solution C gave a metal H (with electron configuration of [Ar]3d84s2).

Identify each of the substances and write balanced chemical equations for each reaction.

From: the CIC examination 2007, part C, Problem 3b.

Of course, it's somewhat an outdated problem, and quite straightforward to solve (says the pseudo-second-year* university student) given some familiarity with descriptive chemistry. I mean, nowadays if you want to know what the sample is, well, just dissolve it and throw the thing in an ICP or an AA for elemental composition. Because the sample happens to have a simple, stoichiometric formula, it's easy to figure out what the empirical formula actually is. Of course, reality is more complicated even if we assume a "pure" sample. (E.g. the problem might be more evil if the metal is iron, because the sample could be pyrite or pyrrhotite).

But I like this problem. It's cute. Unlike the other problems in the exam. It'd be much more fun/crazy (if much less efficient) to identify a substance this way, too. Acids! Flames! Halogens! Strong oxidants and reductants! Dangerous products! Whee! It'll also be edifying: the reactions themselves are good introductions to redox, descriptive, and main-group chemistry, and actually performing the experiments will make one realize that nothing ever works out the way they should. Oh, one assumption on that "dichromate paper" (shouldn't it be orange, anyway?): the paper should be acidic.

In addition, the sample itself is indeed, really quite shiny. Gotta love that, too.

Incidentally, the project is still kicking my ass. My supervisor will not be pleased (I don't know what to say to him...eep.).

*I say pseudo-second-year because the Registrar somehow managed to get even that wrong. Anyway, technically I am done with second year. (Yay?)