To calculate the theoretical yield, we need to first determine the limiting reactant. We can do this by comparing the moles of each reactant to the stoichiometry of the balanced chemical equation.The balanced chemical equation for the reaction between hydrazine N2H4 and 2,4-dinitrochlorobenzene C6H3ClN2O4 is:N2H4 + C6H3ClN2O4 C6H3N4O4 + HClNow, let's find the moles of each reactant:Molar mass of N2H4 = 2 14.01 + 4 1.01 = 32.05 g/molMoles of N2H4 = 0.25 g / 32.05 g/mol = 0.0078 molMolar mass of C6H3ClN2O4 = 6 12.01 + 3 1.01 + 35.45 + 2 14.01 + 4 16.00 = 202.56 g/molMoles of C6H3ClN2O4 = 0.45 g / 202.56 g/mol = 0.0022 molNow, we can compare the mole ratios to the stoichiometry of the balanced equation:Mole ratio of N2H4 to C6H3ClN2O4 = 0.0078 mol / 0.0022 mol = 3.55Since the stoichiometry of the balanced equation is 1:1, hydrazine N2H4 is in excess, and 2,4-dinitrochlorobenzene C6H3ClN2O4 is the limiting reactant.Now, we can calculate the theoretical yield of 2,4-dinitrophenylhydrazine C6H3N4O4 :Moles of C6H3N4O4 = moles of limiting reactant = 0.0022 molMolar mass of C6H3N4O4 = 6 12.01 + 3 1.01 + 4 14.01 + 4 16.00 = 198.14 g/molTheoretical yield of C6H3N4O4 = 0.0022 mol 198.14 g/mol = 0.436 gSo, the theoretical yield of 2,4-dinitrophenylhydrazine is 0.436 grams, assuming 100% conversion efficiency and complete reaction.