16.3.1 The elemental substances of Cr, Mo and W Group VIB elements:Cr,Mo,W Valence electron configuration: Cr,Mo:(n-1)d5nsl,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 ) 16.3.1 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℃] a2CrOa(s) H20 Na,CO;(s) 02① Fe2O3(s) 浸取 Na CrO w一8 H2S04 Na2Cr20 1③ (aq) 酸化 ② carbon C,00 ①4Fe(Cr02)2+8Na2C03+702 2Fe203+8Na2Cr04+8C02 ② 2Na2CrO+H2SO-Na2Cr2O7+Na2SO+H2O ③Na2Cr20,+2C→Cr203+Na2C03+C0 ④2Al+Cr2032Cr+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 Cr3+(紫) 2Cr+2H2S04(浓)→Cr(S04)3+3S02+H,O Chromium will be passivated in both hot and cold concentrated nitric acid
Chromium will be passivated in both hot and cold concentrated nitric acid 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 + 2H 2SO 4 ( 浓 ) → Cr （ 2 SO 4 ） 3 + 3SO 2 + H 2 O Cr + 2H + → Cr2+ + H 2 2. The properties of elemental Cr
The element potential diagram of Cr ER/V Cr2031.33Cr3+-0.41Cr2+-0.91Cr -0.74 E唱/V CrO-0.12 Cr(OH)11 Cr(OH):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
16.3.2 The compounds of chromium Cr,03(铬绿) color mp./℃ changes when heated 250℃分解为 CrO3(铬酐) 暗红色 198 Cr203与02 K,CrO4 黄色 975 熔融不分解 K2Cr202(红矾) 橙红色 398 熔融不分解 Cr203(铬绿) 绿色 2330 不分解 CrCl36H2O 紫色 83 失去结晶水 KCr(S04)212H0 暗紫色 89 失去结晶水上
color m.p./℃ changes when heated CrO3 (铬酐) 暗红色 198 250℃分解为 Cr2O3与O2 K2CrO4 黄色 975 熔融不分解 K2Cr2O7 (红矾) 橙红色 398 熔融不分解 Cr2O3 (铬绿) 绿色 2330 不分解 CrCl3·6H2O 紫色 83 失去结晶水 KCr(SO4)2·12H2O 暗紫色 89 失去结晶水 Cr2O3 (铬绿) 16.3.2 The compounds of chromium