The balanced chemical equation for the preparation of 2,4-dichloronitrobenzene from nitrobenzene and chlorine gas is:C6H5NO2 + 2 Cl2 C6H3Cl2NO2 + 2 HClTo calculate the theoretical yield, we first need to determine the limiting reactant. We will do this by calculating the moles of each reactant and comparing their mole ratios.Molar mass of nitrobenzene C6H5NO2 = 123.11 g/molMolar mass of chlorine gas Cl2 = 70.90 g/molMolar mass of 2,4-dichloronitrobenzene C6H3Cl2NO2 = 202.00 g/molMoles of nitrobenzene = 10 g / 123.11 g/mol = 0.0812 molMoles of chlorine gas = 20 g / 70.90 g/mol = 0.282 molNow, we will compare the mole ratios of the reactants:Mole ratio of nitrobenzene to chlorine gas = 0.0812 mol / 0.282 mol = 0.288Since the balanced equation requires a 1:2 ratio of nitrobenzene to chlorine gas, and the actual ratio is less than that, nitrobenzene is the limiting reactant.Now, we can calculate the theoretical yield of 2,4-dichloronitrobenzene:Moles of 2,4-dichloronitrobenzene = 0.0812 mol nitrobenzene * 1 mol 2,4-dichloronitrobenzene / 1 mol nitrobenzene = 0.0812 molTheoretical yield = 0.0812 mol * 202.00 g/mol = 16.4 gSo, the theoretical yield of 2,4-dichloronitrobenzene is 16.4 g.