A 65.00 mL solution of 0.4950 M AgNO3 was added to a solution of AsO3−4 . Ag3AsO4 precipitated and was filtered off. Fe3+ was added and the solution was titrated with 0.2150 M KSCN . After 38.00 mL of KSCN solution was added, the solution turned red. What mass of AsO3−4 was in the original solution? I know i need to find the original conc of Ag^+ and minus the original from the final to get the final mass