Sciencemadness Discussion Board

Zn + technical HCl = red precipitate?! Selenium?

Draeger - 25-7-2020 at 05:32

So, a few days ago I decided to make some ZnCl2. I mixed the stoichiometric amounts and let it react. I smelt heavy metal hydrides, but I was told there wouldn't be much produced, so I just put plastic wrap over the top and let it stand.

Now, a few days later, I noticed a tiny metal mirror, which is hopefully just zinc. Some zinc remained, so I added a bit more HCl.

Well, a few days later there's this red precipitate.

Here's a picture:


Could it be selenium, or is it just copper?

[Edited on 25-7-2020 by Draeger]

RogueRose - 25-7-2020 at 08:34

It looks like copper to my. I found that zinc is excellent at dissolving metals and I suspect that is what is in there. If it was a zinc alloy, it might have been mixed with aluminum as well as I have many zinc alloys that have both Al and Cu.

Draeger - 25-7-2020 at 09:09

Quote: Originally posted by RogueRose  
It looks like copper to my. I found that zinc is excellent at dissolving metals and I suspect that is what is in there. If it was a zinc alloy, it might have been mixed with aluminum as well as I have many zinc alloys that have both Al and Cu.

My zinc has 99,8% purity, so I doubt it would precipitate that much copper. Maybe it's the HCl?

Tsjerk - 25-7-2020 at 09:20

How do you know how much is there? I highly doubt this is from your HCl. Is it colorless?

Draeger - 25-7-2020 at 10:46

I can see how much is there by just looking. The entire ground of the beaker is covered, with some thickness. And it can only be from the HCl, since there's only 200mg of impurity in the zinc if Onyxmet is to be trusted. The HCl is pretty noticeably green.

Edit: I didn't look correctly. The precipitate is very thin. Maybe it is the 200mg.

Edit: fixed number
[Edited on 25-7-2020 by Draeger]

[Edited on 25-7-2020 by Draeger]

CharlieA - 25-7-2020 at 15:39

Looks can be deceiving...:D