7.
已知重铬酸钾\(\rm{(K_{2}Cr_{2}O_{7})}\)溶液中存在如下平衡:\(\rm{Cr_{2}O_{7}}\) \(\rm{{\,\!}^{2-}(}\)橙色\(\rm{)+H_{2}O⇌2H^{+}+2CrO_{4}^{2-}}\) \(\rm{(}\)黄色\(\rm{)}\),
\(\rm{①}\)向\(\rm{2mL}\) \(\rm{0.1mol⋅L^{-1}}\) \(\rm{K_{2}Cr_{2}O_{7}}\)溶液中滴入\(\rm{3}\)滴\(\rm{6mol⋅L^{-1}}\) \(\rm{NaOH}\)溶液,溶液由橙色变为黄色;向所得溶液中再滴入\(\rm{5}\)滴浓\(\rm{H_{2}SO_{4}}\),溶液由黄色变为橙色
\(\rm{②}\)向\(\rm{2mL}\) \(\rm{0.1mol⋅L^{-1}}\) 酸化的\(\rm{K_{2}Cr_{2}O_{7}}\)溶液中滴入适量\(\rm{(NH_{4})_{2}Fe(SO_{4})_{2}}\)溶液,溶液由橙色变为绿色,发生反应:\(\rm{Cr_{2}O_{7}}\) \(\rm{{\,\!}^{2-}+14H^{+}+6Fe^{2+}=2Cr^{3+}(}\)绿色\(\rm{)+6Fe^{3+}+7H_{2}O.}\)
下列分析正确的是\(\rm{(}\) \(\rm{)}\)