In the process  (in aq medium), initially there are 2 mole I2 & 2 mole I- . But at equilibrium, due to addition of AgNO3(aq), 1.75 mole yellow ppt is obtained. KC for the process is (Vflask=1 dm3) nearly

Initial moles of I2 = 2Initial moles of I - = 2Volume of the vessel = 1 litreYellow ppt formed by the addition of AgNO3 is AgINumber moles of AgI precepitated at equilibrium = 1.75number of moles of I- at equilibrium = 1.75Number of moles of I- reacted = (2 -1.75) = 0.25According to stoichiometry1 mole of I2 reacts with 1 mole of I-x mole of I2 reacts with 0.25 moles of I-Similarly moles of formed due to the reaction of 0.25 moles each of I2 & I- will 0.25