The correct option is A 85%
20 mL of the same stock solution of KI requires 30 mL of M10KIO3.
50 mL of the same stock solution of KI requires 30×5020=75 mL of M10KIO3.
Out of this, 50 mL is required for reaction with excess KI.
Hence, 75−50=25 mL of KIO3 corresponds to the KI that has reacted with AgNO3.
1 mole KIO3=2 mole KI =2moleAgNO3
Number of moles of AgNO3=2×2510×1000=0.005 moles
Mass of AgNO3=0.005×169.87=0.85 g
The percentage of silver nitrate in the sample =0.851×100=85 %.