Properties and Oxidation States of Chromium
– Chromium is a shiny metal.
– It forms a thin coating of chromium(III) oxide when exposed to air, preventing further rusting.
– Chromium has multiple oxidation states, including +2, +3, and +6.
– Chromium compounds are known for their colorful nature.
– Specific compounds include chromium(II) oxide (black, reducing agent), chromium(II) chloride (blue when dissolved in water, unstable), chromium(III) oxide (dark green), chromium(III) chloride (green when hydrated, purple when anhydrous), chromium(IV) oxide (black, used in cassettes), chromium(VI) oxide (red, toxic), chromyl chloride (red liquid), chrome alum, and trivalent chromium compound.
Chromium Compounds
– Chromium compounds have various oxidation states, including +2, +3, and +6.
– Chromium(II) oxide is black and acts as a reducing agent.
– Chromium(II) chloride appears blue when dissolved in water but is unstable.
– Chromium(III) oxide is dark green in color.
– Chromium(III) chloride is green when hydrated and purple when anhydrous.
Trivalent Chromium
– Trivalent chromium is one of the main types of chromium ions found in compounds.
– It is essential for the proper functioning of the human body and other animals.
– Adequate intake of trivalent chromium is necessary for maintaining bodily functions.
– Chromium is obtained from food sources, and supplements are used to ensure sufficient intake.
– Excessive intake of trivalent chromium can be harmful to the body.
Hexavalent Chromium
– Hexavalent chromium, also known as chromate, is another type of chromium ion in the +6 oxidation state.
– Exposure to hexavalent chromium can cause cancer and illness.
– Industries involved in chromium metal production require proper cleanup due to the presence of hexavalent chromium.
– Hexavalent chromium can be converted into trivalent chromium by reacting it with reducing agents.
– Chromates, which contain the chromate ion (CrO4), are generally yellow in color, while dichromates, containing the dichromate ion (Cr2O7), are red or orange.
Occurrence and Preparation of Chromium
– Chromium occurs as chromite, a mixture of iron(II) oxide and chromium(III) oxide.
– Chromite (FeCr2O4) is heated with sodium carbonate to produce sodium chromate, iron(III) oxide, and carbon dioxide.
– Sodium chromate is then reacted with sulfuric acid to obtain sodium dichromate.
– Sodium dichromate is reduced by carbon to yield chromium(III) oxide.
– Chromium metal is obtained by reacting chromium(III) oxide with aluminum.Sources: https://simple.wikipedia.org/wiki/Chromium
