21 The elements of chromium and Manganese family 21.1 The elemental substances of Cr,Mo and W 21.2 The compounds of chromium 21.3 The elemental substance of Mn -21.4 The compounds of manganese
21.2 The compounds of chromium 21.1 The elemental substances of Cr, Mo and W §21 The elements of chromium and Manganese family 21.3 The elemental substance of Mn 21.4 The compounds of manganese
21.1 The elemental substances of Cr, Mo and W Group VIB elements:Cr,Mo,W Valence electron configuration: Cr,Mo:(n-1)d5ns1,W:5d46s2 1.The preparation of elemental Cr (the hardest metal It exists in the form of chromite Fe(CrO2)2 (铬铁矿)
Group VIB elements：Cr, Mo, W It exists in the form of chromite Fe(CrO2 )2 (铬铁矿) 1. The preparation of elemental Cr (the hardest metal ) 21.1 The elemental substances of Cr, Mo and W Valence electron configuration： Cr, Mo: (n-1)d5ns1 , W: 5d46s2
+3 Fe(CrO2)2(s) 1000℃~1300℃ Na,CrOa(s) H20 NazCO3(s) 02① Fe203(s) 浸取 Na2CrO4 ·8 H2S04 Na2Cr2O 7③ (aq) ② carbon( ①4Fe(Cr02)2+8Na2C03+702 2Fe203+8Na2Cr04+8C02 ②2Na2CrO4+H2S04→Na2Cr202+Na2S04+H2O 3Na,Cr2O+2C-Cr2O3+Na2CO3+CO ④2Al+Cr203→2Cr+Al203
1000 ℃ ~1300℃ ① H2O 浸取 H2SO4 酸化 ② Cr2O3 Cr Al ④ Fe(CrO2 )2 (s) Na2CO3 (s) Na2CrO4 (s) Fe2O3 (s) Na2CrO4 (aq) Na2Cr2O7 (aq) Na2Cr2O7 K2Cr2O7 ③ 2Fe 2O3 8Na 2CrO4 8CO2 + + 2 2 8Na 2CO3 7O2 ① 4Fe(CrO ) + + ② 2Na 2CrO4 + H2SO4 Na 2Cr2O7 +Na 2SO4 +H2O 2Al Cr2O3 2Cr Al2O3 ④ + + ③ Na 2Cr2O7 + 2C Cr2O3 + Na 2CO3 + CO +3 O2 carbon
2.The properties of elemental Cr 1 Offwhite,the hardest metal,high m.p and b.p 2 Reactive metal,the formation of a layer of oxide protects the metal from further attack 3Pure metal reacts with acids Cr+2Ht→Cr2++H2 02 Cr3+(紫) 2Cr+2HS04(浓)→Cr2(S04)3+3S02+H2O Chromium will be passivated in both hot and cold concentrated nitric acid HNO
Chromium will be passivated in both hot and cold concentrated nitric acid HNO3 ③ Pure metal reacts with acids ② Reactive metal, the formation of a layer of oxide protects the metal from further attack ① Offwhite, the hardest metal, high m.p and b.p Cr ( ) 2 3+ 紫 O 2Cr + 2H2 SO4 (浓) Cr（2 SO4 ）3 +3SO2 + H2 O Cr + 2H+ Cr2+ + H2 2. The properties of elemental Cr
The element potential diagram of Cr ER/V Cr2031.33Cr3+-041Cr2+-0.91Cr -0.74 E唱/V Cro01 Cr(OH)Cr(OB),14-Cr -1.3
• The element potential diagram of Cr Cr O Cr Cr Cr 2 3 2 2 7 - + + -0.74 1.33 -0.41 -0.91 CrO Cr(OH) Cr(OH) Cr 4 2 2 4 - -0.12 - -1.1 -1.4 -1.3 EB / V EA / V