How many milliliters of 0.635M K2CrO4 are needed to precipitate all the silver in 410mL of 0.158M AgNO3 as AgCrO4 ?

Answer 1

2AgNO3 + K2CrO4 ==> Ag2CrO4 + 2KNO3

How many mols AgNO3 do you have? That's M x L = 0.158*0.410 = about 0.065 but you do it more accurately than that.
That requires 1/2 that K2CrO4 or about 0.032 (look at the coefficients in the balanced equation).
Then M K2CrO4 = mols K2CrO4/L K2CrO4. You have mols and M, solve for L and convert to mL