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Specialty Chemistry Forums => Chemical Engineering Forum => Topic started by: Jayasudha on January 06, 2014, 10:02:14 PM

Title: Copper
Post by: Jayasudha on January 06, 2014, 10:02:14 PM

Hi all,

Am working in Electroplating Company.I have a small doubt in Copper Chloride formation

Can anyone just tell, how does copper change its color when react wito HCL and how it formed

Title: Re: Copper
Post by: Borek on January 07, 2014, 02:58:48 AM

Generally speaking copper doesn't react with HCl, so it is not clear what your question is about.

I guess you wonder why copper compounds are blue or green - that would require you to learn ligand field theory or crystal field theory.

Title: Re: Copper
Post by: Jayasudha on January 07, 2014, 03:24:32 AM

Hi,
Thanks for your suggestion.i go through the Crystal field theory but i can't get the answer
can you explain me why copper not react with HCL or Is Copper react with Nitric?

Title: Re: Copper
Post by: Borek on January 07, 2014, 05:58:23 AM

Quote from: Jayasudha on January 07, 2014, 03:24:32 AM

can you explain me why copper not react with HCL or Is Copper react with Nitric?

This in turn is about reactivity series.

Title: Re: Copper
Post by: Hunter2 on January 07, 2014, 08:11:44 AM

Quote from: Borek on January 07, 2014, 05:58:23 AM

Quote from: Jayasudha on January 07, 2014, 03:24:32 AM

can you explain me why copper not react with HCL or Is Copper react with Nitric?

This in turn is about reactivity series.

Look copper is more noble as hydrogen. Look the table of electro potentials of elements.

http://hyperphysics.phy-astr.gsu.edu/hbase/tables/electpot.html

Title: Re: Copper
Post by: Jayasudha on January 07, 2014, 10:23:45 AM

Thanks, its difficult to understand.Can anyone explain in a easy way?

Title: Re: Copper
Post by: Borek on January 07, 2014, 11:43:16 AM

Easy way: copper is not reactive enough to react with HCl.

Can't address "why" without talking about reactivity series.

Title: Re: Copper
Post by: Enthalpy on January 07, 2014, 11:43:45 AM

Simple acids attack metals by their H⁺ ion. The atom from the solid metal gives an electron to the H⁺ and becomes a positive ion in solution while neutral hydrogen is formed, first as atoms then as molecules, which bubble during the reaction.

The electrode potential is a measure of how favourable this reaction is. Referring to the linked table: potassium is very prone to this attack, even in neutral water; zinc as well; copper is rather resistant; gold is very resistant. At + potentials you find noble metals, wearable as jewellery on the skin and useable as electric contacts, and which may even exist as metallic ore rather than oxides.

Some acids work through other means in addition to H⁺. For instance nitric acid is an oxidizer. Then the previous scheme doesn't apply easily.

Some (many!) metals also have different behaviours than expected from the electrode potential. Aluminium, titanium, chromium, tantalum... develop a hard and tight oxide layer that prevents the reaction. This suffices against sweet or sea water (aluminium), many acids (chromium), or most chemicals (tantalum). This mechanism is extremely dependent on tiny sub-details of the alloy and its condition; for instance 13% chromium make a steel stainless, but if the weld seam must resist corrosion we may specify <0.02% carbon rather than <0.06%.

Title: Re: Copper
Post by: Jayasudha on January 07, 2014, 01:28:30 PM

yes..yes...thanks really understandable....

we doing acid and alkaline zinc plating. We hangout the Zinc anode in copper rod for better conductivity.
I always wonder in acid zinc bath the copper rod rapidly turns blue colour where the alkaline bath the copper not affected.

now i get the idea why it happen like that...thank you so much....