potassium chromate or potassium hromovoloknisty (international name: Kalium chromicum, Kaliumchromat, Potassium chromate) - is an inorganic compound, yellow crystals of rhombic system, water-soluble.It refers to salts H2CrO4 chromic acid, which in the free state exists.In substance potassium chromate following formula: CrK2O4
How to get potassium chromate?
Hromovoloknisty potassium obtained in several ways:
1. By oxidation of chromium oxide, potassium chlorate (the reaction takes place at a temperature of 500-700 degrees):
Cr2O3 (chromium oxide) + KClO3 (potassium chlorate) + K2CO3 (potassium carbonate) =2K2CrO4 (potassium chromate) + KCl (potassium chloride) + 2CO2 (carbonic acid gas)
2. By dissolving the chromium oxide in potassium hydroxide:
CrO3 (chromium oxide) + 2KOH (potassium hydroxide) = K2CrO4 (potassium chromate) + H2O(water)
3. By the decomposition of potassium dichromate by heating (the reaction is carried out at a temperature of 500-600 degrees):
4K2Cr2O7 (potassium dichromate) = 4K2CrO4 (potassium chromate) + 2Cr2O3 (chromium oxide) + 3O2 (oxygen)
4. By acting a concentrated solution of potassium hydroxide to potassium dichromate:
K2Cr2O7 (potassium dichromate) + 2KOH (potassium hydroxide) = 2K2CrO4 (potassium chromate) + H2O (water)
5. In nature rare mineral which is called "tarapakait. "It hromovoloknisty potassium alloy.
chemical properties of potassium chromate:
1. In dilute acids hromovoloknisty potassium enters potassium dichromate, whose formula K2Cr2O7.An example is the following reaction:
2K2CrO4 (potassium chromate) + 2HCl (hydrochloric acid diluted) = K2Cr2O7 (potassium dichromate) + 2KCl (potassium chloride) + H2O (water)
2. In the reaction with concentrated acids occurs alreadyother reaction, for example:
K2CrO4 (potassium chromate) + 2HCl (hydrochloric acid in concentrated form) = K (Cr (Cl) O3) (complex chromium compound) + KCl (potassium chloride) + H2O (water)
3.In conjunction with hot concentrated acids, potassium chromate exhibits oxidative properties.An example is the following reaction is carried out at a temperature of 90 degrees:
2K2CrO4 (potassium chromate) + 16HCl (Hydrochloric acid) = 2CrCl3 (chromium chloride) + 3Cl2 (chlorine as a gas) + 4KCl (potassium chloride) + 8H2O (water)
4. Hromovoloknisty potassium may enter into exchange reactions.For example:
K2CrO4 (potassium chromate) + 2AgNO3 (silver nitrate) = Ag2CrO4 (chromate silver precipitates) + 2KNO3 (potassium nitrate)
K2CrO4 (potassium chromate) + Hg2 (NO3) 2 (mercuric nitrate) = Hg2CrO4 (chromate of mercury precipitates) + 2KNO3 (potassium nitrate)
physical properties of potassium chromate:
1. Its density is 2.732 g / cm3.
2. Potassium chromate is melted at a temperature of 968,3 ° C.At a temperature of 668 degrees becomes red hexagonal phase - acquires a different color - red.However, when cooled again becomes yellow.
3. Forms yellow crystals rhombic system.
4. It belongs to the space group P-nam.
5. Refers to the paramagnetic.6.
poorly soluble in ethanol, insoluble in water.Insoluble in ethyl alcohol and diethyl.
7. The molar mass of 194.19 g / mol.
optical properties of potassium chromate:
The refractive index of 1,74
Where applicable potassium chromate?
1. The leather industry is used as a tanning agent.When dyeing of fabrics used as a mordant.
2. It is used as a component of the composition of electrolytes special chemical degreasing.
3. As whitener waxes and oils.
4. In organic synthesis as an oxidant, such as the manufacture of dyes.
5. Also hromovoloknisty potassium is used to prepare a solution of the electrochemical oxidation of silver, and for passage of products from alloys of copper and silver.
6. In medicine, used as a homeopathic remedy.
7. In laboratories dishwashing is a mixture of equal volumes of concentrated sulfuric acid solution and K2Cr2O7, pre-saturated in the cold.
Potassium dichromate (the technical name - Chrompick)
is a crystal red-orange color.No crystalline forms, has a density of 2.684 gram per cubic centimeter, melts at 397 degrees.With further heating decomposes.Solubility in water at 20 degrees is equal to 12.48 grams of salt per 100 grams of water.Potassium dichromate has been widely used as an oxidizer in pyrotechnics, match industry and hromametrii as a reagent.
