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5 B boron; use: 2.08 g/cm 3: CR2 ... 5.5 g/cm 3: 24 Cr chromium; use: ... 25 Mn manganese; use: 5.95 g/cm 3: CR2 (at m.p.) 5.95 g/cm 3: 26 Fe iron; use: 6.98 g/cm 3 ...
Chromium is a member of group 6 of the transition metals. The +3 and +6 states occur most commonly within chromium compounds, followed by +2; charges of +1, +4 and +5 for chromium are rare, but do nevertheless occasionally exist. [3] [4]
It is obtained on a vast scale by roasting chromium ores in air in the presence of sodium carbonate: 2Cr 2 O 3 + 4 Na 2 CO 3 + 3 O 2 → 4 Na 2 CrO 4 + 4 CO 2. This process converts the chromium into a water-extractable form, leaving behind iron oxides.
Historically, the mole was defined as the amount of substance in 12 grams of the carbon-12 isotope.As a consequence, the mass of one mole of a chemical compound, in grams, is numerically equal (for all practical purposes) to the mass of one molecule or formula unit of the compound, in daltons, and the molar mass of an isotope in grams per mole is approximately equal to the mass number ...
The anhydrous form of chromium(II) acetate, and also related chromium(II) carboxylates, can be prepared from chromocene: 4 RCO 2 H + 2 Cr(C 5 H 5) 2 → Cr 2 (O 2 CR) 4 + 4 C 5 H 6. This method provides anhydrous derivatives in a straightforward manner. [8] Because it is so easily prepared, Cr 2 (OAc) 4 (H 2 O) 2 is a
Chromium(II) sulfate is an inorganic compound with the chemical formula Cr S O 4. It often comes as hydrates CrSO 4 ·nH 2 O. Several hydrated salts are known. The pentahydrate CrSO 4 ·5H 2 O is a blue solid that dissolves readily in water. Solutions of chromium(II) are easily oxidized by air to Cr(III) species.
For example, 50 g of zinc will react with oxygen to produce 62.24 g of zinc oxide, implying that the zinc has reacted with 12.24 g of oxygen (from the Law of conservation of mass): the equivalent weight of zinc is the mass which will react with eight grams of oxygen, hence 50 g × 8 g/12.24 g = 32.7 g.
Chromium triiodide is prepared by the direct reaction of chromium metal with an excess of iodine. The reaction is conducted at 500 °C: 2 Cr + 3 I 2 → 2 CrI 3. To obtain high purity samples, the product is thermally decomposed at 700 °C to sublime out chromium(II) iodide. The diiodide is then reiodinated. [2]