The balanced chemical equation for the synthesis of 2,4-dichloronitrobenzene from nitrobenzene and chlorine gas is:C6H5NO2 + 2 Cl2 C6H3Cl2NO2 + 2 HClNitrobenzene C6H5NO2 reacts with chlorine gas Cl2 to form 2,4-dichloronitrobenzene C6H3Cl2NO2 and hydrogen chloride HCl .