错误:
%28NH4%292Cr2O7 %2B KOH %3D %28NH4%292CrO4 %2B K2CrO4 %2B H2O
^
不需要的字符 ('%')%28NH4%292Cr2O7 %2B KOH %3D %28NH4%292CrO4 %2B K2CrO4 %2B H2O
^
不需要的字符 ('%')