重铬酸钾(K 2 Cr 2 O 7 )是工业生产和实验室的重要氧化剂,工业上常用铬铁矿(主要成份为FeO?Cr 2 O 3

2025-03-15 17:13:09
推荐回答(1个)
回答1:

(1)根据反应的元素化合价变化可知,反应中Cl元素的化合价由+5价降到-1价,反应中得电子,所以KClO 3 为反应中的氧化剂,根据氧化还原反应中氧化剂和还原剂得失电子数目相等可写出反应的化学方程式为6FeO?Cr 2 O 3 +24NaOH+7KClO 3
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12Na 2 CrO 4 +3Fe 2 O 3 +7KCl+12H 2 O,则Na 2 CrO 4 的系数是12,故答案为:KClO 3 ;12;
(2)Al 2 O 3 与纯碱反应转变为可溶性盐,生成NaAlO 2 ,反应的化学方程式为Al 2 O 3 +Na 2 CO 3
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2NaAlO 2 +CO 2 ↑,NaFeO 2 能强烈水解,为强碱弱酸液,水解呈碱性,生成氢氧化铁沉淀,反应的离子方程式为FeO 2 - +2H 2 O=Fe(OH) 3 ↓+OH -
故答案为:Al 2 O 3 +Na 2 CO 3
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2NaAlO 2 +CO 2 ↑;FeO 2 - +2H 2 O=Fe(OH) 3 ↓+OH -
(3)由于硅酸钠和偏铝酸钠在溶液中发生水解,SiO 3 2- +H 2





HSiO 3 - +OH - 、HSiO 3 - +H 2





H 2 SiO 3 +OH - 、AlO 2 - +2H 2





Al(OH) 3 +OH - ,降低pH有利于水解平衡向正反应方向移动,当pH调到7~8时能使它们完全水解生成沉淀,
故答案为:H 2 SiO 3 、Al(OH) 3
(4)由反应Cr 2 O 7 2- +6I - +14H + =2Cr 3+ +3I 2 +7H 2 O;I 2 +2S 2 O 3 2- =2I - +S 4 O 6 2- 可得反应的关系式为Cr 2 O 7 2- ~3I 2 ~6S 2 O 3 2- ,根据关系式计算.
     Cr 2 O 7 2- ~3I 2 ~6S 2 O 3 2-
     1mol   3mol  6mol
      n           cV 2 ×10 -3 mol
n=
c V 2 × 10 -3 mol
6
,则Vml含重铬酸钾的物质的量为
V
V 1
×
c V 2 × 10 -3 mol
6
,则所得产品中重铬酸钾纯度为
294×c×V× V 2
6×1000× V 1 ×m
×100%

故答案为:
294×c×V× V 2
6×1000× V 1 ×m
×100%

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