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topic 54322

Will copper dissolve in hydrochloric acid under 100 °C?




February 10, 2010

I did a lab the other day in grade 11 chemistry class. I put copper wire in HCl in a test tubeand it didn't react. I heated it up in a water bath at 100 °C ( possibly higher) and I saw bubbles along the copper. Thinking it was only water bubbles I shook it off of the copper in the test tube. But the bubbles reappeared slowly. Is this really hydrogen bubbles or is it just more water bubbles coming back?

Tian X.
student - Chatham, Ontario, Canada


February 12, 2010

Tian,

First of all you need to do the chemical equation for the reaction between hydrochloric acid and copper. Now, would you expect hydrogen to be produced?

What concentration of hydrochloric acid were you using? Generally, at a school level you will be using reasonably dilute acid. Now, what would you expect to happen to the reaction rate when you raise the temperature? There is a general rule of thumb for the change in temperature effects on reaction rate. If you can't find it ask your science teacher. By the way, unless you are below sea level or the vessel is under pressure you can assume that the water boils at 100 centigrade.

Finally, there is only one way to prove what gas is being generated on the wire and that is to collect and test it. Common reactions are: a lighted splint will "pop" in the presence of hydrogen, a glowing splint will relight in the presence of oxygen, most other gases and vapours will extinguish a lighted splint (including water vapour).

Best of luck in finding your answers.

Brian Terry
Aerospace - Yeovil, Somerset, UK


March 13, 2010

Copper is a base metal. Dissolve in only nitric or sulphuric acid. HCl is used to remove oxidation layer on copper.

Bhupesh Mulik
jewelry - Mumbai, India


March 16, 2010

The purpose of the lab experiment is to see visually what you can find in a good reference book like the handbook of chemistry and physics. It will tell you that copper metal (clean)is very slightly soluble in HCl. The chapter on rates of reactions will show you that raising the temperature of MOST solutions will raise the rate of the reaction. So, you saw what is a given in a good reference book.

James Watts
- Navarre, Florida



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