Chemical Cell

Chemical Cell: When making a Chemical Cell (Year 9 Energy—Electricity) using a Zinc electrode and a carbon electrode in Acidified Potassium Dichromate, what molarity should the Dichromate be and how much Sulfuric acid (and what molarity) do I add to it to acidify it?

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Publication Date: 14 October 2014
Asked By: ESHS
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Answer by labsupport on question Answer by labsupport on question Answer by delese on question Chemical Cell

Thank you for your question.  The members of the ASSIST team have no direct experience with this particular activity.  We are, however, very concerned about the potential use of potassium dichromate in a Year 9 activity because of its extremely hazardous nature.  It is highly toxic, a known sensitiser, and has evidence of carcinogenic and teratogenic effects (1).  In a school science setting, potassium dichromate use would normally be limited to senior chemistry practicals and be under strict supervision. 

If the purpose of the activity is to demonstrate a chemical cell generating a small electric current, then we strongly recommend that another activity using safer chemicals be substituted.  There are many possibilities here including

  • Al and Cu electrodes with salt water solution
  • Cu and Zn electrodes with copper & zinc sulfate solution 
  • Fruit batteries using lemons, kiwi fruit

A web search on electrochemistry experiments will locate useful websites such as those below which include such activities:

Since your question is about making chemical cells, we hope that this answer has helped.

(1) Safety Data Sheet: http://www.chemsupply.com.au/ProdSearch.aspx?Search=potassium%20dichromate&SearchType=contains

Answer by Karin on question Chemical Cell

I have never heard of a prac that uses dichromate to make an electro-chemical  cell. Dichromate is toxic and carcinogenic, I wouldn't use it for year 9s.

A much safer way of making a cell would be to make the good old Daniell cell, this site has a good write up about it. 

http://www.nuffieldfoundation.org/sites/default/files/11_Cells_and_batte...

You can substitute the copper and zinc sulfate with copper and zinc nitrate (all 1M solutions), the salt bridge should be made from potassium sulfate or nitrate to correspond with the anion used in the cell. 

If the only purpose of the prac is to show students that the cell produces a voltage, you can further increase the safety of the prac by reducing the concentrations of the copper and zinc to 0.1M.

 

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