Question #862f2

1 Answer
Stefan V.
Feb 4, 2016

Not by the reaction between potassium chloride, potassium dichromate, and concentrated sulfuric acid.

Explanation:

Chlorine gas, #"Cl"_2#, is not obtained by heating potassium chloride, #"KCl"#, potassium dichromate, #"K"_2"Cr"_2"O"_7#, and concentrated sulfuric acid, #"H"_2"SO"_4#.

This reaction is actually called the chromyl chloride test for the chloride anion, #"Cl"^(-)#.

The idea is that when you heat a compound that contains chloride (a solid salt, not a solution that contains the solvated anion) with potassium dichromate and concentrated sulfuric acid, the reaction produces chromyl chloride, #"CrO"_2"Cl"_2#, a red fuming liquid.

The balanced chemical equation for this reaction is

#4"KCl"_text((s]) + "K"_2"Cr"_2"O"_text(7(s]) + "H"_2"SO"_text(4(aq]) stackrel(color(red)(Delta)color(white)(aa))(->) 6"KHSO"_text(4(aq]) + 2"CrO"_2"Cl"_text(2(g]) + 3"H"_2"O"_text((l])#

Mind you, this is kind of an overall description of the reaction.

Here's what's actually going on - the sulfuric acid reacts with the potassium chloride and potassium dichromate separately to produce hydrochloric acid, #"HCl"#, and chromium trioxide, #"CrO"_3#, respectively.

#"KCl" + "H"_2"SO"_4 -> "KHSO"_4 + "HCl"#

#"K"_2"Cr"_2"O"_7 + 2"H"_2"SO"_4 -> 2"KHSO"_4 + 2"CrO"_3 + "H"_2"O"#

It is then the reaction between hydrochloric acid and chromium trioxide that produces chromyl chloride.

#2"HCl" + "CrO"_3 -> "CrO"_2"Cl"_2 + "H"_2"O"#

If you add these equations together (and balance them out), you'll get the chemical equation that describes the overall reaction.

I think that some chlorine gas can actually be produced here as a side-product of the reaction, but even if that happens this reaction will still qualify as your answer.

Here's a very cool video detailing the reaction

All the other reactions produce chlorine gas, #"Cl"_2#, as a major product.

Potassium permanganate, #"KMnO"_4#, will react with concentrated hydrochloric acid to form potassium chloride, #"KCl"#, mangane(II) chloride, #"MnCl"_2#, chlorine gas, and water.

http://socratic.org/questions/how-to-balance-an-equation-in-its-molecular-form-eg-kmno4-hcl-gives-kcl-mncl2-h2

Manganese dioxide, #"MnO"_2#, will react with concentrated hydrochloric acid to produce manganese(II) chloride, chlorine gas, and water

http://socratic.org/questions/hcl-is-added-to-following-oxides-which-one-would-give-h2o2-1-mno2-2-pbo2-3-bao2-

Finally, potassium chloride will react with fluorine gas to form chlorine gas and potassium fluoride, #"KF"#

#"KCl"_text((s]) + "F"_text(2(g]) -> 2"KF"_text((s]) + "Cl"_text(2(g])#

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