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已知重铬酸钾( K 2 Cr 2 O 7 )溶液中存在如下平衡: Cr 2 O 7 2- (橙色) + H 2 O 2H + + 2 CrO 4 2- (黄色) 1 向 2 mL 0.1 mol·L -1 K 2 Cr 2 O 7 溶液中滴入 3滴6 mol·L -1 NaOH 溶液,溶液由橙色变为黄色;向所得溶液中再滴入 5滴浓 H 2 SO 4 ,溶液由黄色变为橙色。 2 向 2 mL 0.1 mol·L -1 酸化的 K 2 Cr 2 O 7 溶液中滴入适量 (NH 4 ) 2 Fe(SO 4 ) 2 溶液,溶液由橙色变为绿色,发生反应: Cr 2 O 7 2- + 14H + + 6Fe 2+ === 2Cr 3+ ( 绿色 ) + 6Fe 3+ + 7H 2 O 。 下列分析正确的是 ( ) A .实验 1和2均能证明K 2 Cr 2 O 7 溶液中存在上述平衡 B .实验 2能说明氧化性: Cr 2 O 7 2- > Fe 3+ C . CrO 4 2- 和 Fe 2+ 在酸性溶液中可以大量共存 D .稀释 K 2 Cr 2 O 7 溶液时,溶液中各离子浓度均减小
A.
．实验①和②均能证明K 2 Cr 2 O 7 溶液中存在上述平衡
B.
．实验②能说明氧化性： Cr 2 O 7 2- > Fe 3+
C.
． CrO 4 2- 和Fe 2+ 在酸性溶液中可以大量共存
D.
．稀释 K 2 Cr 2 O 7 溶液时，溶液中各离子浓度均减小
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