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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: aoibhd on January 25, 2019, 07:09:34 AM

Title: Oxidation of Ethanol by Chromium (VI) calculations
Post by: aoibhd on January 25, 2019, 07:09:34 AM

If anyone could help me I would really appreciate it.
Im struggling to calculate the concentration of HCrO4- in the stock solution K2Cr2O7.
The concentration of the stock solution is 0.0037M in 3.6 M HCl.

Any help would be great,
Thanks,
aoibh

Title: Re: Oxidation of Ethanol by Chromium (VI) calculations
Post by: Borek on January 25, 2019, 07:57:45 AM

In concentrated HCl solution most of the chromic acid is already dehydrated to dichromate, so you will need to deal with a multistep equilibrium in a solution that has a very high ionic strength. It can be quite challenging to find out the exact equilibrium for such a solution.

What do you need it for?

Title: Re: Oxidation of Ethanol by Chromium (VI) calculations
Post by: aoibhd on January 25, 2019, 08:27:57 AM

I need the initial concentration in order to calculate the number of moles of HCrO4- during the oxidation of ethanol over time.

Title: Re: Oxidation of Ethanol by Chromium (VI) calculations
Post by: Borek on January 25, 2019, 05:37:43 PM

But why specifically HCrO₄^-? Why not Cr(VI) total?

Title: Re: Oxidation of Ethanol by Chromium (VI) calculations
Post by: chenbeier on January 26, 2019, 01:39:58 PM

Additionally dichromate will be reduced by HCl ,creating Chlorine.  Normaly sulfuric acid is used.

For the ethanol oxidation only the amount of Cr(VI) is neccessary.