碘在科研与生活中有重要应用,某兴趣小组用\(\rm{0.50mol⋅L^{-1}}\) \(\rm{KI}\)、\(\rm{0.2\%}\)淀粉溶液、\(\rm{0.20mol⋅L^{-1}}\) \(\rm{K_{2}S_{2}O_{8}}\)、\(\rm{0.10mol⋅L^{-1}}\) \(\rm{Na_{2}S_{2}O_{3}}\)等试剂,探究反应条件对化学反应速率的影响.
已知:
\(\rm{S_{2}O_{8}^{2-}+2I^{-}⇌2SO_{4}^{2-}+I_{2}(}\)慢\(\rm{)}\)
\(\rm{I_{2}+2S_{2}O_{3}^{2-}⇌2I^{-}+S_{4}O_{6}^{2-}(}\)快\(\rm{)}\)
\(\rm{(1)}\)向\(\rm{KI}\)、\(\rm{Na_{2}S_{2}O_{3}}\)与淀粉的混合溶液中加入一定量的\(\rm{K_{2}S_{2}O_{8}}\)溶液,当溶液中的 ______
耗尽后,溶液颜色将由无色变为蓝色
\(\rm{(2)}\)为探究反应物浓度对化学反应速率的影响,设计的实验方案如表:
实验序号 | 体积\(\rm{V/mL}\) |
\(\rm{K_{2}S_{2}O_{8}}\)溶液 | 水 | \(\rm{KI}\)溶液 | \(\rm{Na_{2}S_{2}O_{3}}\)溶液 | 淀粉溶液 |
\(\rm{①}\) | \(\rm{10.0}\) | \(\rm{0.0}\) | \(\rm{4.0}\) | \(\rm{4.0}\) | \(\rm{2.0}\) |
\(\rm{②}\) | \(\rm{9.0}\) | \(\rm{1.0}\) | \(\rm{4.0}\) | \(\rm{4.0}\) | \(\rm{2.0}\) |
\(\rm{③}\) | \(\rm{8.0}\) | \(\rm{V_{x}}\) | \(\rm{4.0}\) | \(\rm{4.0}\) | \(\rm{2.0}\) |
表中\(\rm{V_{x}=}\) ______ \(\rm{mL}\),理由是 ______
.