7.
在恒温、恒容的密闭容器中进行反应\(\rm{2H_{2}O_{2} \dfrac { \overset{\;MnO_{2}\;}{}}{\;}2H_{2}O+O_{2}↑.}\)若\(\rm{H_{2}O_{2}}\)溶液的浓度由\(\rm{2.0mol⋅L^{-1}}\)降到\(\rm{1.0mol⋅L^{-1}}\)需\(\rm{10s}\),那么\(\rm{H_{2}O_{2}}\)浓度由\(\rm{1.0mol⋅L^{-1}}\)降到\(\rm{0.5mol⋅L^{-1}}\)所需的反应时间为\(\rm{(}\) \(\rm{)}\)