Error:
%28NH4%292Cr2O7 %3D Cr2O3 %2B NH3 %2B O2 %2B H2O
^
Unexpected character ('%')%28NH4%292Cr2O7 %3D Cr2O3 %2B NH3 %2B O2 %2B H2O
^
Unexpected character ('%')