Chapter 19: Problem 11

How will you prepare the following? (a) Chromyl chloride (b) Potassium chromate (c) Pure \(\mathrm{MnO}_{2}\) (d) Sodium cobaltinitrite (e) Prussian blue

Short Answer

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Chromyl Chloride is prepared by heating potassium dichromate with common salt and concentrated sulphuric acid. Potassium chromate is obtained by reacting potassium dichromate with potassium hydroxide. Pure \(\mathrm{MnO}_2\) can be prepared by decomposing potassium permanganate at high temperatures. Sodium cobaltinitrite is prepared by reacting cobalt (II) chloride with sodium nitrite in the presence of sodium acetate. Lastly, Prussian blue is prepared by mixing solutions of ferric chloride and potassium ferrocyanide.

Step by step solution

Preparation of Chromyl Chloride

Chromyl chloride is prepared by heating potassium dichromate salt and common salt together in the presence of concentrated sulphuric acid. This is followed by distillation to separate chromyl chloride. The reaction is as follows:\[\mathrm{K}_{2}\mathrm{Cr}_{2}\mathrm{O}_{7}+4\mathrm{NaCl}+6\mathrm{H}_{2}\mathrm{SO}_{4}\rightarrow 2\mathrm{CrO}_{2}\mathrm{Cl}_{2}+2\mathrm{KHSO}_{4}+4\mathrm{NaHSO}_{4}+3\mathrm{H}_{2}\mathrm{O}\]

Preparation of Potassium Chromate

Potassium chromate is prepared by reacting potassium dichromate with potassium hydroxide. The reaction is as follows:\[\mathrm{K}_{2}\mathrm{Cr}_{2}\mathrm{O}_{7}+2\mathrm{KOH}\rightarrow 2\mathrm{K}_{2}\mathrm{CrO}_{4}+\mathrm{H}_{2}\mathrm{O}\]

Preparation of Pure \(\mathrm{MnO}_2\)

Pure \(\mathrm{MnO}_2\) can be prepared by decomposition of potassium permanganate at high temperature. The reaction is as follows:\[2\mathrm{KMnO}_{4}\rightarrow\mathrm{K}_{2}\mathrm{MnO}_{4}+\mathrm{MnO}_{2}+\mathrm{O}_{2}\]

Preparation of Sodium Cobaltinitrite

Sodium cobaltinitrite is prepared by the reaction of cobalt (II) chloride with sodium nitrite in the presence of sodium acetate under specific conditions, that include heating the reaction mixture at 60–70 degrees Celsius for 4-5 hours. Here is the reaction:\[\mathrm{CoCl}_{2}+6\mathrm{NaNO}_{2}+2\mathrm{CH}_{3}\mathrm{COONa}\rightarrow\mathrm{Na}_{3}\mathrm{Co}\left(\mathrm{NO}_{2}\right)_{6}+2\mathrm{CH}_{3}\mathrm{COOH}+2\mathrm{NaCl}\]

Preparation of Prussian Blue

Prussian blue can be prepared by mixing solutions of ferric chloride and potassium ferrocyanide. This will result in the formation of a deep blue precipitate, known as Prussian blue. Here is the chemical equation:\[2\mathrm{FeCl}_{3}+3\mathrm{K}_{4}\left[\mathrm{Fe}\left(\mathrm{CN}\right)_{6}\right]\rightarrow\mathrm{Fe}_{4}\left[\mathrm{Fe}\left(\mathrm{CN}\right)_{6}\right]_{3}+\mathrm{KCl}\]

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How will you prepare the following? (a) Chromyl chloride (b) Potassium chromate (c) Pure \(\mathrm{MnO}_{2}\) (d) Sodium cobaltinitrite (e) Prussian blue

Short Answer

Step by step solution

Preparation of Chromyl Chloride

Preparation of Potassium Chromate

Preparation of Pure \(\mathrm{MnO}_2\)

Preparation of Sodium Cobaltinitrite

Preparation of Prussian Blue

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