sodium dichromate reactions

Anxurus · Post by **Anxurus** » Fri Jan 08, 2010 8:15 am

What are the products of the reaction of sodium dichromate and water
Na₂Cr₂O₇ + H₂₀

What are the products of the reaction of sodium dichromate, water and sodium phosphate
Na₂Cr₂O₇ + H₂₀ + Na₂HPO₄

What are the products of the reaction of sodium dichromate, water and sodium monophosphate
Na₂Cr₂O₇ + H₂₀ + NaH₂PO₄

What are the products of the reaction of sodium dichromate, water and sodium silicate
Na₂Cr₂O₇ + H₂₀ + Na₂SiO₃

What are the products of the reaction of sodium dichromate, water and CMC
Na₂Cr₂O₇ + H₂₀ + C₈H₁₆O₈

expert · Post by **expert** » Fri Jan 08, 2010 8:58 am

Na₂Cr₂O₇ + H₂₀ <==> Na₂CrO₄ + H₂CrO₄ - simple hydrolysis

Na₂Cr₂O₇ + H₂₀ + Na₂HPO₄ --> Na₂CrO₄ + NaH₂PO₄

Na₂Cr₂O₇ + H₂₀ + NaH₂PO₄ --/--> no reaction

Na₂Cr₂O₇ + H₂₀ + Na₂SiO₃ --> Na₂CrO₄ + H₂SiO₃ (silica gel)

Na₂Cr₂O₇ + H₂₀ + C₈H₁₆O₈

Carboxymethyl celulose is a reducer http://en.wikipedia.org/wiki/Carboxymethyl_cellulose
while Na₂Cr₂O₇ is an oxidizer. In proper conditions (in the presence of extra acid) sodium bichromate will completely oxidize CMC:

Na₂Cr₂O₇ + H₂SO₄ + C₈H₁₆O₈ --> Na₂SO₄ + Cr₂(SO₄)₃ + CO₂ + H₂O

In the absence of acid will be partial oxidation with undefined products

Anxurus · Post by **Anxurus** » Fri Jan 08, 2010 10:25 am

Thanks a lot for your greta help.
I have used the same equations in this website to balnce the equations you provided me. These arethe balanced equations

Na₂Cr₂O₇ + H₂₀ <==> Na₂CrO₄ + H₂CrO₄
Na₂Cr₂O₇ + H₂O = Na₂CrO₄ + H₂CrO₄

Na₂Cr₂O₇ + H₂₀ + Na₂HPO₄ --> Na₂CrO₄ + NaH₂PO₄
Na₂Cr₂O₇ + H₂O + 2 Na₂HPO₄ = 2 Na₂CrO₄ + 2 NaH₂PO₄

Na₂Cr₂O₇ + H₂₀ + NaH₂PO₄ --/--> no reaction

Na₂Cr₂O₇ + H₂₀ + Na₂SiO₃ --> Na₂CrO₄ + H₂SiO₃ (silica gel)
Na₂Cr₂O₇ + H₂O + Na₂SiO₃ = 2 Na₂CrO₄ + H₂SiO₃

Na₂Cr₂O₇ + H₂SO₄ + C₈H₁₆O₈ --> Na₂SO₄ + Cr₂(SO₄)₃ + CO₂ + H₂O
16 Na₂Cr₂O₇ + 64 H₂SO₄ + 3 C₈H₁₆O₈ = 16 Na₂SO₄ + 16 Cr₂(SO₄)₃ + 24 CO₂ + 88 H₂O

expert · Post by **expert** » Fri Jan 08, 2010 9:39 pm

OK, good! Make sure you think about these results, not just copy. Don't hesitate to ask why. Main things about bichromates that they are oxidizers and acid salts at the same time. Chromate (Na₂CrO₄ is a neutral salt.

Anxurus · Post by **Anxurus** » Sat Jan 09, 2010 10:44 pm

thanks for the hint,

I will have to ask why?
I don't really knwo the risks of mixing the H₂SO₄ and Sodium dichromate
Please explain
thanks

expert · Post by **expert** » Sun Jan 10, 2010 11:17 am

Please read my previous post on the safety issues with Na₂Cr₂O₇/H₂SO₄ mix and also read this MSDS
http://www.astraldiagnostics.com/MSDS/D ... n_3309.pdf