How does HCL corrode zinc

Experiment of the month
October 2003


If two metals are conductively connected to one another, aLocal element in front. Electrochemical reactions take place particularly quickly on local elements. Local elements therefore play a major role in technology, but also in medicine.

Equipment and chemicals:
2 M copper sulfate solution, zinc sheet, 2 M hydrochloric acid
Beaker, test tube, tripod.

Execution:
A zinc sheet is half immersed in a copper sulfate solution. The sheet is covered with a brown-black copper layer. Place the tray with the copper coating facing up in a test tube filled with dilute hydrochloric acid (or dilute sulfuric acid). An intensive gas development immediately begins, which is strongest at the border between bare zinc sheet and copper coating. In the figure, a strong bubble formation can also be seen in the upper right corner, the point of application of the tweezers.

Explanation:
Zinc is a base metal, so it is attacked by dilute acids. A local element is present through the copper coating. Oxidation and reduction take place spatially separately on a local element. In this reaction, oxidation takes place on the free zinc surface:

Zn Zn2+ + 2 e
The reduction of the protons takes place on the copper:
2 H+ + 2 e H2
The electrons flow through the metal layer between the reaction centers. The current flow is greatest at the border between zinc and copper, and therefore the corrosion is most intense there.

Hints:
Local elements can also be used for corrosion protection.
Local elements can be formed in the oral cavity when amalgam and gold fillings are introduced at the same time.Chemistry for doctors

Hazards:
Copper salts are harmful to health.

Disposal:
The neutralized solutions come to the heavy metal waste.

Literature & Links:
Chemistry internship for physicians: Experiment 5.4
own documents

Mrs Dipl.-Chem. Gisela Martinek, Mr Dipl.-Umw.Wiss. Simon Spycher and mr cand. med. Tobias Vogt I thank you very much for your support.


September 2003: Inertia of the alkanes

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Page created on: Tuesday, September 30, 2003,A. Schunk, CCC Univ. Gain.

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